PART III.

OF THE SUBDIVISION OF PHYSICS INTO DISTINCT BRANCHES, AND THEIR

MUTUAL RELATIONS.

CHAP. I.

Of the Phenomena of Force, and of the Constitution of Natural

Bodies. 221

CHAP. II.

Of the Communication of Motion through Bodies.--Of Sound and

Light. 246

CHAP. III.

Of Cosmical Phenomena. 265

CHAP. IV.

Of the Examination of the material Constituents of the World.

290

CHAP. V.

Of the Imponderable Forms of Matter. 310

CHAP. VI.

Of the Causes of the actual rapid Advance of the Physical

Sciences compared with their Progress at an earlier Period. 347

“In primis, hominis est propria VERI inquisitio atque

investigatio. Itaque cum sumus negotiis necessariis, curisque

vacui, tum avemus aliquid videre, audire, ac dicere,

cognitionemque rerum, aut occultarum aut admirabilium, ad benè

beatéque vivendum necessariam ducimus;--ex quo intelligitur,

quod VERUM, simplex, sincerumque sit, id esse naturæe hominis

aptissimum. Huic veri videndi cupiditati adjuncta est appetitio

quædam principatûs, ut nemini parere animus benè a naturâ

informatus velit, nisi præcipienti, aut docenti, aut utilitatis

causa justè et legitimè imperanti: ex quo animi magnitudo

existit, et humanararum rerum contemtio.”

CICERO, DE OFFICIIS, Lib. 1. § 13.

Before all other things, man is distinguished by his pursuit

and investigation of TRUTH. And hence, when free from needful

business and cares, we delight to see, to hear, and to

communicate, and consider a knowledge of many admirable and

abstruse things necessary to the good conduct and happiness of

our lives: whence it is clear that whatsoever is TRUE, simple,

and direct, the same is most congenial to our nature as men.

Closely allied with this earnest longing to see and know the

truth, is a kind of dignified and princely sentiment which

forbids a mind, naturally well constituted, to submit its

faculties to any but those who announce it in precept or in

doctrine, or to yield obedience to any orders but such as are

at once just, lawful, and founded on utility. From this source

spring greatness of mind and contempt of worldly advantages and

troubles.

PRELIMINARY DISCOURSE

ON

THE STUDY

OF

NATURAL PHILOSOPHY.

PART I.

OF THE GENERAL NATURE AND ADVANTAGES OF THE STUDY OF

THE PHYSICAL SCIENCES

CHAPTER I.

OF MAN REGARDED AS A CREATURE OF INSTINCT, OF REASON, AND

SPECULATION.--GENERAL INFLUENCE OF SCIENTIFIC PURSUITS ON THE

MIND.

(1.) The situation of man on the globe he inhabits, and over which he

has obtained the control, is in many respects exceedingly remarkable.

Compared with its other denizens, he seems, if we regard only his

physical constitution, in almost every respect their inferior, and

equally unprovided for the supply of his natural wants and his defence

against the innumerable enemies which surround him. No other animal

passes so large a portion of its existence in a state of absolute

helplessness, or falls in old age into such protracted and lamentable

imbecility. To no other warm-blooded animal has nature denied that

indispensable covering without which the vicissitudes of a temperate

and the rigours of a cold climate are equally insupportable; and to

scarcely any has she been so sparing in external weapons, whether for

attack or defence. Destitute alike of speed to avoid and of arms to

repel the aggressions of his voracious foes; tenderly susceptible of

atmospheric influences; and unfitted for the coarse aliments which the

earth affords spontaneously during at least two thirds of the year,

even in temperate climates,--man, if abandoned to mere instinct, would

be of all creatures the most destitute and miserable. Distracted by

terror and goaded by famine; driven to the most abject expedients

for concealment from his enemies, and to the most cowardly devices

for the seizure and destruction of his nobler prey, his existence

would be one continued subterfuge or stratagem;--his dwelling would

be in dens of the earth, in clefts of rocks, or in the hollows of

trees; his food worms, and the lower reptiles, or such few and crude

productions of the soil as his organs could be brought to assimilate,

varied with occasional relics, mangled by more powerful beasts of prey,

or contemned by their more pampered choice. Remarkable only for the

absence of those powers and qualities which obtain for other animals a

degree of security and respect, he would be disregarded by some, and

hunted down by others, till after a few generations his species would

become altogether extinct, or, at best, would be restricted to a few

islands in tropical regions, where the warmth of the climate, the

paucity of enemies, and the abundance of vegetable food, might permit

it to linger.

(2.) Yet man is the undisputed lord of the creation. The strongest

and fiercest of his fellow-creatures,--the whale, the elephant, the

eagle, and the tiger,--are slaughtered by him to supply his most

capricious wants, or tamed to do him service, or imprisoned to make

him sport. The spoils of all nature are in daily requisition for his

most common uses, yielded with more or less readiness, or wrested with

reluctance, from the mine, the forest, the ocean, and the air. Such

are the first fruits of reason. Were they the only or the principal

ones, were the mere acquisition of power over the materials, and the

less gifted animals which surround us, and the consequent increase

of our external comforts, and our means of preservation and sensual

enjoyment, the sum of the privileges which the possession of this

faculty conferred, we should after all have little to plume ourselves

upon. But this is so far from being the case, that every one who passes

his life in tolerable ease and comfort, or rather whose whole time

is not anxiously consumed in providing the absolute necessaries of

existence, is conscious of wants and cravings in which the senses have

no part, of a series of pains and pleasures totally distinct in kind

from any which the infliction of bodily misery or the gratification

of bodily appetites has ever afforded him; and if he has experienced

these pleasures and these pains in any degree of intensity, he will

readily admit them to hold a much higher rank, and to deserve much

more attention, than the former class. Independent of the pleasures

of fancy and imagination, and social converse, man is constituted a

speculative being; he contemplates the world, and the objects around

him, not with a passive, indifferent gaze, as a set of phenomena in

which he has no further interest than as they affect his immediate

situation, and can be rendered subservient to his comfort, but as

a system disposed with order and design. He approves and feels the

highest admiration for the harmony of its parts, the skill and

efficiency of its contrivances. Some of these which he can best trace

and understand he attempts to imitate, and finds that to a certain

extent, though rudely and imperfectly, he can succeed,--in others, that

although he can comprehend the nature of the contrivance, he is totally

destitute of all means of imitation;--while in others, again, and those

evidently the most important, though he sees the effect produced,

yet the means by which it is done are alike beyond his knowledge

and his control. Thus he is led to the conception of a Power and an

Intelligence superior to his own, and adequate to the production and

maintenance of all that he sees in nature,--a Power and Intelligence to

which he may well apply the term infinite, since he not only sees no

actual limit to the instances in which they are manifested, but finds,

on the contrary, that the farther he enquires, and the wider his sphere

of observation extends, they continually open upon him in increasing

abundance; and that as the study of one prepares him to understand and

appreciate another, refinement follows on refinement, wonder on wonder,

till his faculties become bewildered in admiration, and his intellect

falls back on itself in utter hopelessness of arriving at an end.

(3.) When from external objects he turns his view upon himself, on his

own vital and intellectual faculties, he finds that he possesses a

power of examining and analysing his own nature to a certain extent,

but no farther. In his corporeal frame he is sensible of a power to

communicate a certain moderate amount of motion to himself and other

objects; that this power depends on his will, and that its exertion

can be suspended or increased at pleasure within certain limits; but

_how_ his will acts on his limbs he has no consciousness: and whence he

derives the power he thus exercises, there is nothing to assure him,

however he may long to know. His senses, too, inform him of a multitude

of particulars respecting the external world, and he perceives an

apparatus by which impressions from without may be transmitted, as a

sort of signals to the interior of his person, and ultimately to his

brain, wherein he is obscurely sensible that the thinking, feeling,

reasoning being he calls _himself_, more especially resides; but by

what means he becomes conscious of these impressions, and what is the

nature of the immediate communication between that inward sentient

being, and that machinery, his outward man, he has not the slightest

conception.

(4.) Again, when he contemplates still more attentively the thoughts,

acts, and passions of this his sentient intelligent self, he finds,

indeed, that he can remember, and by the aid of memory can compare

and discriminate, can judge and resolve, and, above all, that he is

irresistibly impelled, from the perception of any phenomenon without

or within him, to infer the existence of something prior which stands

to it in the relation of a _cause_, without which it would not be, and

that this knowledge of causes and their consequences is what, in almost

every instance, determines his choice and will, in cases where he is

nevertheless conscious of perfect freedom to act or not to act. He

finds, too, that it is in his power to acquire more or less knowledge

of causes and effects according to the degree of attention he bestows

upon them, which attention is again in great measure a voluntary act;

and often when his choice has been decided on imperfect knowledge or

insufficient attention, he finds reason to correct his judgment, though

perhaps too late to influence his decision by after consideration. A

world within him is thus opened to his intellectual view, abounding

with phenomena and relations, and of the highest immediate interest.

But while he cannot help perceiving that the insight he is enabled to

obtain into this internal sphere of thought and feeling is in reality

the source of all his power, the very fountain of his predominance over

external nature, he yet feels himself capable of entering only very

imperfectly into these recesses of his own bosom, and analysing the

operations of his mind,--in this as in all other things, in short, “_a

being darkly wise_;” seeing that all the longest life and most vigorous

intellect can give him power to discover by his own research, or time

to know by availing himself of that of others, serves only to place

him on the very frontier of knowledge, and afford a distant glimpse

of boundless realms beyond, where no human thought has penetrated,

but which yet he is sure must be no less familiarly known to that

Intelligence which he traces throughout creation than the most obvious

truths which he himself daily applies to his most trifling purposes.

Is it wonderful that a being so constituted should first encourage a

hope, and by degrees acknowledge an assurance, that his intellectual

existence will not terminate with the dissolution of his corporeal

frame, but rather that in a future state of being, disencumbered of

a thousand obstructions which his present situation throws in his

way, endowed with acuter senses, and higher faculties, he shall drink

deep at that fountain of beneficent wisdom for which the slight taste

obtained on earth has given him so keen a relish?

(5.) Nothing, then, can be more unfounded than the objection which has

been taken, _in limine_, by persons, well meaning perhaps, certainly

narrow-minded, against the study of natural philosophy, and indeed

against all science,--that it fosters in its cultivators an undue and

overweening self-conceit, leads them to doubt the immortality of the

soul, and to scoff at revealed religion. Its natural effect, we may

confidently assert, on every well constituted mind is and must be

the direct contrary. No doubt, the testimony of natural reason, on

whatever exercised, must of necessity stop short of those truths which

it is the object of revelation to make known; but, while it places

the existence and principal attributes of a Deity on such grounds as

to render doubt impossible, it unquestionably opposes no natural or

necessary obstacle to further progress: on the contrary, by cherishing

as a vital principle an unbounded spirit of enquiry, and ardency of

expectation, it unfetters the mind from prejudices of every kind, and

leaves it open and free to every impression of a higher nature which

it is susceptible of receiving, guarding only against enthusiasm and

self-deception by a habit of strict investigation, but encouraging,

rather than suppressing, every thing that can offer a prospect or a

hope beyond the present obscure and unsatisfactory state. The character

of the true philosopher is to hope all things not impossible, and to

believe all things not unreasonable. He who has seen obscurities which

appeared impenetrable in physical and mathematical science suddenly

dispelled, and the most barren and unpromising fields of enquiry

converted, as if by inspiration, into rich and inexhaustible springs

of knowledge and power on a simple change of our point of view, or

by merely bringing to bear on them some principle which it never

occurred before to try, will surely be the very last to acquiesce in

any dispiriting prospects of either the present or future destinies of

mankind; while, on the other hand, the boundless views of intellectual

and moral as well as material relations which open on him on all hands

in the course of these pursuits, the knowledge of the trivial place he

occupies in the scale of creation, and the sense continually pressed

upon him of his own weakness and incapacity to suspend or modify the

slightest movement of the machinery he sees in action around him, must

effectually convince him that humility of pretension, no less than

confidence of hope, is what best becomes his character.

(6.) But while we thus vindicate the study of natural philosophy from a

charge at one time formidable, owing to the pertinacity and acrimony

with which it was urged, and still occasionally brought forward to

the distress and disgust of every well constituted mind, we must

take care that the testimony afforded by science to religion, be its

extent or value what it may, shall be at least independent, unbiassed,

and spontaneous. We do not here allude to such reasoners as would

make all nature bend to their narrow interpretations of obscure and

difficult passages in the sacred writings: such a course might well

become the persecutors of Galileo and the other bigots of the fifteenth

and sixteenth centuries, but can only be adopted by dreamers in the

present age. But, without going these lengths, it is no uncommon thing

to find persons, earnestly attached to science and anxious for its

promotion, who yet manifest a morbid sensibility on points of this

kind,--who exult and applaud when any fact starts up explanatory (as

they suppose) of some scriptural allusion and who feel pained and

disappointed when the general course of discovery in any department

of science runs wide of the notions with which particular passages in

the Bible may have impressed themselves. To persons of such a frame of

mind it ought to suffice to remark, on the one hand, that truth can

never be opposed to truth, and, on the other, that error is only to be

effectually confounded by searching deep and tracing it to its source.

Nevertheless, it were much to be wished that such persons, estimable

and excellent as many of them are, before they throw the weight of

their applause or discredit into the scale of scientific opinion on

such grounds, would reflect, first, that the credit and respectability

of _any_ evidence may be destroyed by tampering with its _honesty_;

and, secondly, that this very disposition of mind implies a lurking

mistrust in its own principles, since the grand and indeed only

character of truth is its capability of enduring the test of universal

experience, and coming unchanged out of every possible form of _fair_

discussion.

(7.) But if science may be vilified by representing it as opposed to

religion, or trammelled by mistaken notions of the danger of free

enquiry, there is yet another mode by which it may be degraded from

its native dignity, and that is by placing it in the light of a mere

appendage to and caterer for our pampered appetites. The question

“_cui bono_” to what practical end and advantage do your researches

tend? is one which the speculative philosopher who loves knowledge

for its own sake, and enjoys, as a rational being should enjoy, the

mere contemplation of harmonious and mutually dependent truths, can

seldom hear without a sense of humiliation. He feels that there is a

lofty and disinterested pleasure in his speculations which ought to

exempt them from such questioning; communicating as they do to his own

mind the purest happiness (after the exercise of the benevolent and

moral feelings) of which human nature is susceptible, and tending to

the injury of no one, he might surely allege _this_ as a sufficient

and direct reply to those who, having themselves little capacity, and

less relish for intellectual pursuits, are constantly repeating upon

him this enquiry. But if he can bring himself to descend from this

high but fair ground, and justify himself, his pursuits, and his

pleasures in the eyes of those around him, he has only to point to the

history of all science, where speculations, apparently unprofitable,

have, in innumerable instances, been those from which great practical

applications have emanated. What, for instance, could be more so than

the dry speculations of the ancient geometers on the properties of the

conic sections, or than the dreams of Kepler (as they would naturally

appear to his contemporaries) about the numerical harmonies of the

universe? Yet these are the steps by which we have risen to a knowledge

of the elliptic motions of the planets and the law of gravitation,

with all its splendid theoretical consequences, and its inestimable

practical results. The ridicule attached to “_Swing-swangs_” in

Hooke’s time[1] did not prevent him from reviving the proposal of the

_pendulum_ as a standard of measure, since so effectually wrought into

practice by the genius and perseverance of Captain Kater;--nor did

that which Boyle encountered in his researches on the elasticity and

pressure of the air act as any obstacle to the train of discovery which

terminated in the steam-engine. The dreams of the alchemists led them

on in the path of experiment, and drew attention to the wonders of

chemistry, while they brought their advocates (it must be admitted) to

merited contempt and ruin. But in this case it was moral dereliction

which gave to ridicule a weight and power not necessarily or naturally

belonging to it: but among the alchemists were men of superior minds,

who reasoned while they worked, and who, not content to grope always in

the dark, and blunder on their object, sought carefully in the observed

nature of their agents for guides in their pursuit. To these we owe the

creation of experimental philosophy.

(8.) Not that it is meant, by any thing above said, to assert

that there is no such thing as a great or a little in speculative

philosophy, or to place the solution of an enigma on a level with

the developement of a law of nature, still less to adopt the homely

definition of Smith[2], that a philosopher is a person whose trade it

is to do nothing, and speculate on every thing. The speculations of

the natural philosopher, however remote they may for a time lead him

from beaten tracks and every-day uses, being grounded in the realities

of nature, have all, of necessity, a practical application,--nay

more, such applications form the very criterions of their truth,

they afford the readiest and completest verifications of his

theories;--verifications which he will no more neglect to test them by

than an arithmetician would omit to _prove_ his sums, or a cautious

geometer to try his general theorems by particular cases.[3]

(9.) After all, however, it must be confessed, that to minds

unacquainted with science, and unused to consider the mutual

dependencies of its various branches, there is something neither

unnatural nor altogether blamable in the ready occurrence of this

question of direct advantage. It requires some habit of abstraction,

some penetration of the mind with a tincture of scientific enquiry,

some conviction of the value of those estimable and treasured

principles which lie concealed in the most common and homely

facts,--some experience, in fine, of success in developing and placing

them in evidence, announcing them in precise terms, and applying them

to the explanation of other facts of a less familiar character, or to

the accomplishment of some obviously useful purpose:--to cure the mind

of this tendency to rush at once upon its object, to undervalue the

means in over-estimation of the end, and while gazing too intently at

the goal which alone it has been accustomed to desire, to lose sight

of the richness and variety of the prospects that offer themselves on

either hand on the road.

(10.) We must never forget that it is principles, not phenomena,--the

interpretation, not the mere knowledge of facts,--which are the

objects of enquiry to the natural philosopher. As truth is single,

and consistent with itself, a principle may be as completely and as

plainly elucidated by the most familiar and simple fact, as by the

most imposing and uncommon phenomenon. The colours which glitter on

a soap-bubble are the immediate consequence of a principle the most

important from the variety of phenomena it explains, and the most

beautiful, from its simplicity and compendious neatness, in the whole

science of optics. If the nature of periodical colours can be made

intelligible by the contemplation of such a trivial object, from that

moment it becomes a noble instrument in the eye of correct judgment;

and to blow a large, regular, and durable soap-bubble may become the

serious and praiseworthy endeavour of a sage, while children stand

round and scoff, or children of a larger growth hold up their hands

in astonishment at such waste of time and trouble. To the natural

philosopher there is no natural object unimportant or trifling. From

the least of nature’s works he may learn the greatest lessons. The fall

of an apple to the ground may raise his thoughts to the laws which

govern the revolutions of the planets in their orbits; or the situation

of a pebble may afford him evidence of the state of the globe he

inhabits, myriads of ages ago, before his species became its denizens.

(11.) And this is, in fact, one of the great sources of delight

which the study of natural science imparts to its votaries. A mind

which has once imbibed a taste for scientific enquiry, and has

learnt the habit of applying its principles readily to the cases

which occur, has within itself an inexhaustible source of pure and

exciting contemplations:--one would think that Shakspeare had such

a mind in view when he describes a contemplative man as finding all

nature eloquent--the very trees, the brooks, and the stones reading

to him lessons of deep and serious import. Accustomed to trace the

operation of general causes, and the exemplification of general laws,

in circumstances where the uninformed and unenquiring eye perceives

neither novelty nor beauty, he walks in the midst of wonders: every

object which falls in his way elucidates some principle, affords some

instruction, and impresses him with a sense of harmony and order. Nor

is it a mere passive pleasure which is thus communicated. A thousand

questions are continually arising in his mind, a thousand subjects of

enquiry presenting themselves, which keep his faculties in constant

exercise, and his thoughts perpetually on the wing, so that lassitude

is excluded from his life, and that craving after artificial excitement

and dissipation of mind, which leads so many into frivolous, unworthy,

and destructive pursuits, is altogether eradicated from his bosom.

(12.) It is not one of the least advantages of these pursuits, which,

however, they possess in common with every class of intellectual

pleasures, that they are altogether independent of external

circumstances, and are to be enjoyed in every situation in which a man

can be placed in life. The highest degrees of worldly prosperity are so

far from being incompatible with them, that they supply inestimable

advantages for their pursuit, and that sort of fresh and renewed relish

which arises partly from the sense of contrast, partly from experience

of the peculiar pre-eminence they possess over the pleasures of sense

in their capability of unlimited increase and continual repetition

without satiety or distaste. They may be enjoyed, too, in the intervals

of the most active business; and the calm and dispassionate interest

with which they fill the mind renders them a most delightful retreat

from the agitations and dissensions of the world, and from the conflict

of passions, prejudices, and interests in which the man of business

finds himself involved. There is something in the contemplation of

general laws which powerfully induces and persuades us to merge

individual feeling, and to commit ourselves unreservedly to their

disposal; while the observation of the calm, energetic regularity of

nature, the immense scale of her operations, and the certainty with

which her ends are attained, tends, irresistibly, to tranquillize and

re-assure the mind, and render it less accessible to repining, selfish,

and turbulent emotions. And this it does, not by debasing our nature

into weak compliances and abject submission to circumstances, but by

filling us, as from an inward spring, with a sense of nobleness and

power which enables us to rise superior to them; by showing us our

strength and innate dignity, and by calling upon us for the exercise

of those powers and faculties by which we are susceptible of the

comprehension of so much greatness, and which form, as it were, a link

between ourselves and the best and noblest benefactors of our species,

with whom we hold communion in thoughts and participate in discoveries

which have raised them above their fellow-mortals, and brought them

nearer to their Creator.

CHAP. II.

OF ABSTRACT SCIENCE AS A PREPARATION FOR THE STUDY OF PHYSICS.--A

PROFOUND ACQUAINTANCE WITH IT NOT INDISPENSABLE FOR A CLEAR

UNDERSTANDING OF PHYSICAL LAWS.--HOW A CONVICTION OF THEIR TRUTH

MAY BE OBTAINED WITHOUT IT.--INSTANCES.--FURTHER DIVISION OF THE

SUBJECT.

(13.) Science is the knowledge of many, orderly and methodically

digested and arranged, so as to become attainable by one. The knowledge

of reasons and their conclusions constitutes _abstract_, that of causes

and their effects, and of the laws of nature, _natural science_.

(14.) Abstract science is independent of a system of nature,--of a

creation,--of every thing, in short, except memory, thought, and

reason. Its objects are, first, those primary existences and relations

which we cannot even conceive not to _be_, such as space, time,

number, order, &c.; and, secondly, those artificial forms, or symbols,

which thought has the power of creating for itself at pleasure, and

substituting as representatives, by the aid of memory, for combinations

of those primary objects and of its own conceptions,--either to

facilitate the act of reasoning respecting them, or as convenient

deposits of its own conclusions, or for their communication to others.

Such are, first, _language_, oral or written; its conventional forms,

which constitute grammar, and the rules for its use in argument,

in which consists the logic of the schools; secondly, _notation_,

which, applied to _number_, is _arithmetic_,--and, to the more general

relations of abstract quantity or order, is _algebra_; and, thirdly,

that higher kind of logic, which teaches us to use our reason in the

most advantageous manner for the discovery of truth; which points

out the criterions by which we may be sure we have attained it; and

which, by detecting the sources of error, and exposing the haunts where

fallacies are apt to lurk, at once warns us of their danger, and shows

us how to avoid them. This greater logic may be termed _rational_[4];

while, to that inferior department which is conversant with words

alone, the epithet _verbal_[5] may, for distinction, be applied.

(15.) A certain moderate degree of acquaintance with abstract science

is highly desirable to every one who would make any considerable

progress in physics. As the universe exists in time and place; and as

motion, velocity, quantity, number, and order, are main elements of

our knowledge of external things and their changes, an acquaintance

with these, abstractedly considered, (that is to say, independent of

any consideration of the particular things moved, measured, counted,

or arranged,) must evidently be a useful preparation for the more

complex study of nature. But there is yet another recommendation of

such sciences as a preparation for the study of natural philosophy.

Their objects are so definite, and our notions of them so distinct,

that we can reason about them with an assurance, that the words and

signs used in our reasonings are full and true representatives of the

things signified; and, consequently, that when we use language or signs

in argument, we neither, by their use, introduce extraneous notions,

nor exclude any part of the case before us from consideration. For

example: the words space, square, circle, a hundred, &c., convey to

the mind notions so complete in themselves, and so distinct from every

thing else, that we are sure when we use them we know and have in

view the whole of our own meaning. It is widely different with words

expressing natural objects and mixed relations. Take, for instance,

iron. Different persons attach very different ideas to this word. One

who has never heard of magnetism has a widely different notion of

_iron_ from one in the contrary predicament. The vulgar, who regard

this metal as incombustible, and the chemist, who sees it burn with the

utmost fury, and who has other reasons for regarding it as one of the

most combustible bodies in nature;--the poet, who uses it as an emblem

of rigidity; and the smith and engineer, in whose hands it is plastic,

and moulded like wax into every form;--the jailer, who prizes it as

an obstruction, and the electrician, who sees in it only a channel of

open communication by which that most impassable of obstacles, the

air, may be traversed by his imprisoned fluid, have all different, and

all imperfect, notions of the same word. The meaning of such a term

is like a rainbow--every body sees a different one, and all maintain

it to be the same. So it is with nearly all our terms of sense. Some

are indefinite, as hard or soft, light or heavy (terms which were at

one time the sources of innumerable mistakes and controversies); some

excessively complex, as man, life, instinct. But, what is worst of

all, some, nay most, have two or three meanings; sufficiently distinct

from each other to make a proposition true in one sense and false in

another, or even false altogether; yet not distinct enough to keep us

from confounding them in the process by which we arrived at it, or

to enable us immediately to recognise the fallacy when led to it by

a train of reasoning, each step of which we _think_ we have examined

and approved. Surely those who thus attach two senses to one word, or

superadd a new meaning to an old one, act as absurdly as colonists who

distribute themselves over the world, naming every place they come

to by the names of those they have left, till all distinctions of

geographical nomenclature are confounded, and till we are unable to

decide whether an occurrence stated to have happened at Windsor took

place in Europe, America, or Australia.[6]

(16.) It is, in fact, in this double or incomplete sense of words that

we must look for the origin of a very large portion of the errors

into which we fall. Now, the study of the abstract sciences, such as

arithmetic, geometry, algebra, &c., while they afford scope for the

exercise of reasoning about objects that are, or, at least, may be

conceived to be, external to us; yet, being free from these sources

of error and mistake, accustom us to the strict use of language as

an instrument of reason, and by familiarizing us, in our progress

towards truth, to walk uprightly and straight-forward on firm ground,

give us that proper and dignified carriage of mind which could never

be acquired by having always to pick our steps among obstructions

and loose fragments, or to steady them in the reeling tempest of

conflicting meanings.

(17.) But there is yet another point of view under which some

acquaintance with abstract science may be regarded as highly desirable

in general education, if not indispensably necessary, to impress on us

the distinction between strict and vague reasoning, to show us what

demonstration really _is_, and to give us thereby a full and intimate

sense of the nature and strength of the evidence on which our knowledge

of the actual system of nature, and the laws of natural phenomena,

rests. For this purpose, however, a very moderate acquaintance with the

more elementary branches of mathematics may suffice. The chain is laid

before us, and every link is submitted to our unreserved examination,

if we have patience and inclination to enter on such detail. Hundreds

have gone through it, and will continue to do so; but, for the

generality of mankind, it is enough to satisfy themselves of the

solidity and adamantine texture of its materials, and the unreserved

exposure of its weakest, as well as its strongest, parts. If, however,

we content ourselves with this general view of the matter, we must be

content also to take on trust, that is, on the authority of those who

have examined deeper, every conclusion which cannot be made apparent

to our senses. Now, among these there are many so very surprising,

indeed apparently so extravagant, that it is quite impossible for any

enquiring mind to rest contented with a mere hearsay statement of

them,--we feel irresistibly impelled to enquire further into their

truth. What mere assertion will make any man believe, that in one

second of time, in one beat of the pendulum of a clock, a ray of light

travels over 192,000 miles, and would therefore perform the tour of the

world in about the same time that it requires to wink with our eyelids,

and in much less than a swift runner occupies in taking a single

stride? What mortal can be made to believe, without demonstration, that

the sun is almost a million times larger than the earth? and that,

although so remote from us, that a cannon ball shot directly towards

it, and maintaining its full speed, would be twenty years in reaching

it, it yet affects the earth by its attraction in an inappreciable

instant of time?--a closeness of union of which we can form but a

feeble, and totally inadequate, idea, by comparing it to any material

connection; since the communication of an impulse to such a distance,

by any solid intermedium we are acquainted with, would require, not

moments, but whole years. And when, with pain and difficulty we have

strained our imagination to conceive a distance so vast, a force so

intense and penetrating, if we are told that the one dwindles to an

insensible point, and the other is unfelt at the nearest of the fixed

stars, from the mere effect of their remoteness, while among those

very stars are some whose actual splendour exceeds by many hundred

times that of the sun itself, although we may not deny the truth of the

assertion, we cannot but feel the keenest curiosity to know _how_ such

things were ever made out.

(18.) The foregoing are among those results of scientific research

which, by their magnitude, seem to transcend our powers of conception.

There are others, again, which, from their minuteness, would appear

to elude the grasp of thought, much more of distinct and accurate

measurement. Who would not ask for demonstration, when told that a

gnat’s wing, in its ordinary flight, beats many hundred times in a

second? or that there exist animated and regularly organized beings,

many thousands of whose bodies laid close together would not extend an

inch? But what are these to the astonishing truths which modern optical

enquiries have disclosed, which teach us that every point of a medium

through which a ray of light passes is affected with a succession of

periodical movements, regularly recurring at equal intervals, no less

than five hundred millions of millions of times in a single second!

that it is by such movements, communicated to the nerves of our eyes,

that we see:--nay more, that it is the _difference_ in the frequency of

their recurrence which affects us with the sense of the diversity of

colour; that, for instance, in acquiring the sensation of redness our

eyes are affected four hundred and eighty-two millions of millions of

times; of yellowness, five hundred and forty-two millions of millions

of times; and of violet, seven hundred and seven millions of millions

of times per second.[7] Do not such things sound more like the ravings

of madmen, than the sober conclusions of people in their waking senses?

(19.) They are, nevertheless, conclusions to which any one may most

certainly arrive, who will only be at the trouble of examining the

chain of reasoning by which they have been deduced; but, in order

to do this, something beyond the mere elements of abstract science

is required. Waving, however, such instances as these, which, after

all, are rather calculated to surprise and astound than for any other

purpose, it must be observed that it is not possible to satisfy

ourselves completely that we _have_ arrived at a true statement of any

law of nature, until, setting out from such statement, and making it

a foundation of reasoning, we can show, by strict argument, that the

facts observed must follow from it as necessary logical consequences,

and _this_, not vaguely and generally, but with all possible precision

in time, place, weight, and measure.

(20.) To do this, however, as we shall presently see, requires in many

cases a degree of knowledge of mathematics and geometry altogether

unattainable by the generality of mankind, who have not the leisure,

even if they all had the capacity, to enter into such enquiries,

some of which are indeed of that degree of difficulty that they can

be only successfully prosecuted by persons who devote to them their

whole attention, and make them the serious business of their lives.

But there is scarcely any person of good ordinary understanding,

however little exercised in abstract enquiries, who may not be readily

made to comprehend at least the general train of reasoning by which

any of the great truths of physics are deduced, and the essential

bearings and connections of the several parts of natural philosophy.

There are whole branches too and very extensive and important ones, to

which mathematical reasoning has never been at all applied; such as

chemistry, geology, and natural history in general, and many others,

in which it plays a very subordinate part, and of which the essential

principles, and the grounds of application to useful purposes, may

be perfectly well understood by a student who possesses no more

mathematical knowledge than the rules of arithmetic; so that no one

need be deterred from the acquisition of knowledge, or even from

active original research in such subjects, by a want of mathematical

information. Even in those branches which, like astronomy, optics, and

dynamics, are almost exclusively under the dominion of mathematics, and

in which no effectual progress can be made without _some_ acquaintance

with geometry, the principal _results_ may be perfectly understood

without it. To one incapable of following out the intricacies of

mathematical demonstration, the conviction afforded by verified

predictions must stand in the place of that purer and more satisfactory

reliance which a verification of every step in the process of reasoning

can alone afford, since every one will acknowledge the validity of

pretensions which he is in the daily habit of seeing brought to the

test of practice.

(21.) Among the verifications of this practical kind which abound

in every department of physics, there are none more imposing than

the precise prediction of the greater phenomena of astronomy; none,

certainly, which carry a broader conviction home to every mind from

their notoriety and unequivocal character. The prediction of eclipses

has accordingly from the earliest ages excited the admiration of

mankind, and been one grand instrument by which their allegiance (so

to speak) to natural science, and their respect for its professors,

has been maintained; and though strangely abused in unenlightened ages

by the supernatural pretensions of astrologers, the credence given

even to their absurdities shows the force of this kind of evidence on

men’s minds. The predictions of astronomers are, however, now far too

familiar to endanger the just equipoise of our judgment, since even the

return of comets, true to their paths and exact to the hour of their

appointment, has ceased to amaze, though it must ever delight all who

have souls capable of being penetrated by such beautiful instances of

accordance between theory and facts. But the age of mere wonder in

such things is past, and men prefer being guided and enlightened, to

being astonished and dazzled. Eclipses, comets, and the like, afford

but rare and transient displays of the powers of calculation, and of

the certainty of the principles on which it is grounded. A page of

“lunar distances” from the Nautical Almanack is worth all the eclipses

that have ever happened for inspiring this necessary confidence in the

conclusions of science. That a man, by merely measuring the moon’s

apparent distance from a star with a little portable instrument held

in his hand, and applied to his eye, even with so unstable a footing

as the deck of a ship, shall say positively, within five miles, where

he is, on a boundless ocean, cannot but appear to persons ignorant of

physical astronomy an approach to the miraculous. Yet, the alternatives

of life and death, wealth and ruin, are daily and hourly staked with

perfect confidence on these marvellous computations, which might

almost seem to have been devised on purpose to show how closely the

extremes of speculative refinement and practical utility can be brought

to approximate. We have before us an anecdote communicated to us by

a naval officer[8], distinguished for the extent and variety of his

attainments, which shows how impressive such results may become in

practice. He sailed from San Blas on the west coast of Mexico, and

after a voyage of 8000 miles, occupying 89 days, arrived off Rio de

Janeiro, having, in this interval, passed through the Pacific Ocean,

rounded Cape Horn, and crossed the South Atlantic, without making any

land, or even seeing a single sail, with the exception of an American

whaler off Cape Horn. Arrived within a week’s sail of Rio, he set

seriously about determining, by lunar observations, the precise line

of the ship’s course and its situation in it at a determinate moment,

and having ascertained this within from five to ten miles, ran the

rest of the way by those more ready and compendious methods, known to

navigators, which can be safely employed for short trips between one

known point and another, but which cannot be trusted in long voyages,

where the moon is the only sure guide. The rest of the tale we are

enabled by his kindness to state in his own words:--“We steered towards

Rio de Janeiro for some days after taking the lunars above described,

and having arrived within fifteen or twenty miles of the coast, I hove

to at four in the morning till the day should break, and then bore

up; for although it was very hazy, we could see before us a couple of

miles or so. About eight o’clock it became so foggy that I did not

like to stand in farther, and was just bringing the ship to the wind

again before sending the people to breakfast, when it suddenly cleared

off, and I had the satisfaction of seeing the great Sugar Loaf Rock,

which stands on one side of the harbour’s mouth, so nearly right ahead

that we had not to alter our course above a point in order to hit the

entrance of Rio. This was the first land we had seen for three months,

after crossing so many seas and being set backwards and forwards by

innumerable currents and foul winds.” The effect on all on board might

well be conceived to have been electric; and it is needless to remark

how essentially the authority of a commanding officer over his crew may

be strengthened by the occurrence of such incidents, indicative of a

degree of knowledge and consequent power beyond their reach.

(22.) But even such results as these, striking as they are, yet fall

short of the force with which conviction is urged upon us when,

through the medium of reasoning too abstract for common apprehension,

we arrive at conclusions which outrun experience, and describe

beforehand what will happen under new combinations, or even correct

imperfect experiments, and lead us to a knowledge of facts contrary

to received analogies drawn from an experience wrongly interpreted

or overhastily generalised. To give an example:--every body knows

that objects viewed through a transparent medium, such as water or

glass, appear distorted or displaced. Thus, a stick in water appears

bent, and an object seen through a prism or wedge of glass seems to

be thrown aside from its true place. This effect is owing to what is

called the _refraction_ of light; and a simple rule discovered by

Willebrod Snell enables any one to say exactly _how much_ the stick

will be bent, and _how far_, and in what _direction_, the apparent

situation of an object seen through the glass will deviate from the

real one. If a shilling be laid at the bottom of a basin of water

and viewed obliquely, it will appear to be raised by the water; if

instead of water spirits of wine be used it will appear more raised;

if oil, still more:--but in none of these cases will it appear to be

thrown _aside_ to the _right_ or _left_ of its true place, however

the eye be situated. The _plane_, in which are contained the eye,

the object, and the point in the surface of the liquid at which the

object is seen, is an upright or _vertical_ plane; and this is one of

the principal characters in the _ordinary refraction_ of light, viz.

that the ray by which we see an object through a refracting surface,

although it undergoes a bending, and is, as it were, broken at the

surface, yet, in pursuing its course to the eye, does not _quit a plane

perpendicular to the refracting surface_. But there are again other

substances, such as rock-crystal, and especially Iceland spar, which

possess the singular property of _doubling_ the image or appearance

of an object seen through them in certain directions; so that instead

of seeing one object we see two, side by side, when such a crystal or

spar is interposed between the object and the eye; and if a ray or

small sunbeam be thrown upon a surface of either of these substances,

it will be split into two, making an angle with each other, and each

pursuing its own separate course,--this is called _double refraction_.

Now, of these images or doubly refracted rays, one always follows

the same rule as if the substance were glass or water: its deviation

can be correctly calculated by Snell’s law above mentioned, and it

does not quit the plane perpendicular to the refracting surface. The

other ray, on the contrary, (which is therefore said to have undergone

_extraordinary refraction_) _does_ quit that plane, and the amount of

its deviation from its former course requires for its determination a

much more complicated rule, which cannot be understood or even stated

without a pretty intimate knowledge of geometry. Now, rock-crystal

and Iceland spar differ from glass in a very remarkable circumstance.

They affect naturally certain regular figures, not being found in

shapeless lumps, but in determinate geometrical forms; and they are

susceptible of being cleft or split much easier in certain directions

than in others--they have a _grain_ which glass has not. When other

substances having this peculiarity (and which are called _crystallized_

substances) were examined, they were all, or by far the greater part,

found to possess this singular property of _double refraction_; and

it was very natural to conclude, therefore, that the same thing took

place in all of them, viz. that of the two rays, into which any beam of

light falling on the surface of such a substance was split, or of the

two images of an object seen through it, _one_ only was turned aside

out of its _plane_ and _extraordinarily_ refracted, while the other

followed the _ordinary_ rule. Accordingly this was supposed to be the

case; and not only so, but from some trials and measurements purposely

made by a philosopher of great eminence, it was considered to be a fact

sufficiently established by experiment.

(23.) Perhaps we might have remained long under this impression, for

the measurements are delicate, and the subject very difficult. But

it has lately been demonstrated by an eminent French philosopher and

mathematician, M. Fresnel, that, granting certain _principles_ or

postulates, all the phenomena of double refraction, including perhaps

the greatest variety of facts that have ever yet been arranged under

one general head, may be satisfactorily explained and deduced from them

by strict mathematical calculation; and _that_, when applied to the

cases first mentioned, these principles give a satisfactory account

of the _want_ of the extraordinary image; _that_ when applied to such

cases as those of rock-crystal or Iceland spar, they also give a

correct account of both the images, and agree in their conclusions with

the rules before ascertained for them: but so far from coinciding with

that part of the previous statement, which would make these conclusions

extend to all crystallised substances, M. Fresnel’s principles lead

to a conclusion quite opposite, and point to a _fact_ which had never

been observed, viz. that in by far the greater number of crystallized

substances which possess the property of double refraction, _neither_

of the images follows the ordinary law, but both undergo a deviation

from their original plane. Now this had never been observed to be

the case in any previous trial, and all opinion was against it. But

when put to the test of experiment in a great variety of new and

ingenious methods, it was found to be fully verified; and to complete

the evidence, the substances on whose imperfect examination the

first erroneous conclusion was founded, having been lately subjected

to a fresh and more scrupulous examination, the result has shown

the insufficiency of the former measurements, and proved in perfect

accordance with the newly discovered laws. Now it will be observed

in this case, first, that, so far from the principles assumed by M.

Fresnel being at all obvious, they are extremely remote from ordinary

observation; and, secondly, that the chain of reasoning by which they

are brought to the test is one of such length and complexity, and the

purely mathematical difficulty of their application so great, that

no _mere_ good common sense, no general tact or ordinary practical

reasoning, would afford the slightest chance of threading their

mazes. Cases like this are the triumph of theories. They show at once

how large a part pure reason has to perform in our examination of

nature, and how implicit our reliance ought to be on that powerful and

methodical system of rules and processes which constitute the modern

mathematical analysis, in all the more difficult applications of exact

calculation to her phenomena.

(24.) To take an instance more within ordinary apprehension. An

eminent living geometer had proved by calculations, founded on strict

optical principles, that in the _centre of the shadow_ of a small

circular plate of metal, exposed in a dark room to a beam of light

emanating from a _very small brilliant point_, there ought to be no

darkness,--in fact, _no shadow_ at that place; but, on the contrary, a

degree of illumination precisely as bright as if the metal plate were

away. Strange and even impossible as this conclusion may seem, it has

been put to the trial, and found perfectly correct.[9]

(25.) We shall now proceed to consider more particularly, and in

detail,--

I. The nature and objects immediate and collateral of physical

science, as regarded in itself, and in its application to

the practical purposes of life, and its influence on the

well-being and progress of society.

II. The principles on which it relies for its successful

prosecution, and the rules by which a systematic examination

of nature should be conducted, with examples illustrative of

their influence.

III. The subdivision of physical science into distinct branches,

and their mutual relations.

CHAP. III.

OF THE NATURE AND OBJECTS, IMMEDIATE AND COLLATERAL, OF PHYSICAL

SCIENCE, AS REGARDED IN ITSELF, AND IN ITS APPLICATION TO THE

PRACTICAL PURPOSES OF LIFE, AND ITS INFLUENCE ON THE WELL-BEING

AND PROGRESS OF SOCIETY.

(26.) The first thing impressed on us from our earliest infancy is,

that events do not succeed one another at random, but with a certain

degree of order, regularity, and connection;--some constantly, and, as

we are apt to think, immutably,--as the alternation of day and night,

summer and winter,--others contingently, as the motion of a body from

its place, if pushed, or the burning of a stick if thrust into the

fire. The knowledge that the former class of events _has_ gone on,

uninterruptedly, for ages beyond all memory, impresses us with a strong

expectation that it will continue to do so in the same manner; and

thus our notion of an _order of nature_ is originated and confirmed.

If every thing were equally regular and periodical, and the succession

of events liable to no change depending on our own will, it may be

doubted whether we should ever think of looking for causes. No one

regards the night as the cause of the day, or the day of night. They

are alternate effects of a common cause, which their regular succession

alone gives us no sufficient clue for determining. It is chiefly,

perhaps entirely, from the other or contingent class of events that

we gain our notions of cause and effect. From them alone we gather

that there are such things as laws of nature. The very idea of a law

includes that of contingency. “_Si quis mala carmina condidisset, fuste

ferito_;” if such a case arise, such a course shall be followed,--if

the match be applied to the gunpowder, it will explode. Every law is a

provision for cases which _may_ occur, and has relation to an infinite

number of cases that never have occurred, and never will. Now, it is

this provision, _à priori_, for contingencies, this contemplation

of possible occurrences, and predisposal of what shall happen, that

impresses us with the notion of a _law_ and a _cause_. Among all the

possible combinations of the fifty or sixty elements which chemistry

shows to exist on the earth, it is likely, nay almost certain, that

_some_ have never been formed; that some elements, in some proportions,

and under some circumstances, have never yet been placed in relation

with one another. Yet no chemist can doubt that it is _already fixed_

what they will do when the case does occur. They will obey certain

laws, of which we know nothing at present, but which must _be_ already

fixed, or they could not be laws. It is not by habit, or by trial

and failure, that they will learn what to do. When the contingency

occurs, there will be no hesitation, no consultation;--their course

will at once be decided, and will always be the same if it occur ever

so often in succession, or in ever so many places at one and the same

instant. This is the perfection of a law, that it includes all possible

contingencies, and ensures implicit obedience,--and of this kind are

the laws of nature.

(27.) This use of the word _law_, however, our readers will of course

perceive has relation to us as understanding, rather than to the

materials of which the universe consists as obeying, certain rules.

To obey a law, to act in _compliance_ with a rule, supposes an

understanding and a will, a power of complying or not, in the being who

obeys and complies, which we do not admit as belonging to mere matter.

The Divine Author of the universe cannot be supposed to have laid down

particular laws, enumerating all individual contingencies, which his

materials have understood and obey,--this would be to attribute to

him the imperfections of human legislation;--but rather, by creating

them, endued with certain fixed qualities and powers, he has impressed

them in their origin with the _spirit_, not the _letter_, of his law,

and made all their subsequent combinations and relations inevitable

consequences of this first impression, by which, however, we would no

way be understood to deny the constant exercise of his direct power in

maintaining the system of nature, or the ultimate emanation of every

energy which material agents exert from his immediate will, acting in

conformity with his own laws.

(28.) The discoveries of modern chemistry have gone far to establish

the truth of an opinion entertained by some of the ancients, that

the universe consists of distinct, separate, indivisible _atoms_,

or individual beings so minute as to escape our senses, except when

united by millions, and by this aggregation making up bodies of even

the smallest visible bulk; and we have the strongest evidence that,

although there exist great and essential differences in individuals

among these atoms, they may yet all be arranged in a very limited

number of groups or classes, all the individuals of each of which

are, to all intents and purposes, _exactly alike_ in all their

properties. Now, when we see a great number of things precisely alike,

we do not believe this similarity to have originated except from a

common principle independent of them; and that we recognise this

likeness, chiefly by the identity of their deportment under similar

circumstances, strengthens rather than weakens the conclusion. A line

of spinning-jennies[10], or a regiment of soldiers dressed exactly

alike, and going through precisely the same evolutions, gives us no

idea of independent existence: we must see them act out of concert

before we can believe them to have independent wills and properties,

not impressed on them from without. And this conclusion, which would

be strong even were there only two individuals precisely alike in

_all_ respects and _for ever_, acquires irresistible force when their

number is multiplied beyond the power of imagination to conceive. If

we mistake not, then, the discoveries alluded to effectually destroy

the idea of an _eternal self-existent matter_, by giving to each of its

atoms the essential characters, at once, of a _manufactured article_,

and a _subordinate agent_.

(29.) But to ascend to the origin of things, and speculate on the

creation, is not the business of the natural philosopher. An humbler

field is sufficient for him in the endeavour to discover, as far

as our faculties will permit, what _are_ these primary qualities

originally and unalterably impressed on matter, and to discover the

_spirit_ of the laws of nature, which includes groups and classes of

relations and facts from the _letter_ which, as before observed, is

presented to us by single phenomena: or if, after all, this should

prove impossible; if such a step be beyond our faculties; and the

essential qualities of material agents be really _occult_, or incapable

of being expressed in any form intelligible to our understandings, at

least to approach as near to their comprehension as the nature of the

case will allow; and devise such forms of words as shall include and

_represent_ the greatest possible multitude and variety of phenomena.

(30.) Now, in this research there would seem one great question to

be disposed of before our enquiries can even be commenced with any

thing like a prospect of success, which is, whether the laws of

nature themselves _have_ that degree of permanence and fixity which

can render them subjects of systematic discussion; or whether, on the

other hand, the qualities of natural agents are subject to mutation

from the lapse of time. To the ancients, who lived in the infancy of

the world, or rather, in the infancy of man’s experience, this was a

very rational subject of question, and hence their distinctions between

corruptible and incorruptible matter. Thus, according to some among

them, the matter only of the celestial spaces is pure, immutable, and

incorruptible, while all sublunary things are in a constant state of

lapse and change; the world becoming paralysed and effete with age,

and man himself deteriorating in character, and diminishing at once in

intellectual and bodily stature. But to us, who have the experience

of some additional thousands of years, the question of permanence is

already, in a great measure, decided in the affirmative. The refined

speculations of modern astronomy, grounding their conclusions on

observations made at very remote periods, have proved to demonstration,

that one at least of the great powers of nature, the force of

gravitation, the main bond and support of the material universe, has

undergone no change in intensity from a high antiquity. The stature of

mankind is just what it was three thousand years ago, as the specimens

of mummies which have been examined at various times sufficiently

show. The intellect of Newton, Laplace, or Lagrange, may stand in

fair competition with that of Archimedes, Aristotle, or Plato; and the

virtues and patriotism of Washington with the brightest examples of

ancient history.

(31.) Again, the researches of chemists have shown that what the

vulgar call corruption, destruction, &c., is nothing but a change of

arrangement of the same ingredient elements, the disposition of the

same materials into other forms, without the loss or actual destruction

of a single atom; and thus any doubts of the permanence of natural

laws are discountenanced, and the whole weight of _appearances_ thrown

into the opposite scale. One of the most obvious cases of apparent

destruction is, when any thing is ground to dust and scattered to the

winds. But it is one thing to grind a fabric to powder, and another to

annihilate its materials: scattered as they may be, they must fall

somewhere, and continue, if only as ingredients of the soil, to perform

their humble but useful part in the economy of nature. The destruction

produced by fire is more striking: in many cases, as in the burning

of a piece of charcoal or a taper, there is no smoke, nothing visibly

dissipated and carried away; the burning body wastes and disappears,

while nothing _seems_ to be produced but warmth and light, which we

are not in the habit of considering as substances; and when all has

disappeared, except perhaps some trifling ashes, we naturally enough

suppose it is gone, lost, destroyed. But when the question is examined

more exactly, we detect, in the invisible stream of heated air which

ascends from the glowing coal or flaming wax, the _whole_ ponderable

matter, only united in a new combination with the air, and dissolved in

it. Yet, so far from being thereby destroyed, it is only become again

what it was before it existed in the form of charcoal or wax, an active

agent in the business of the world, and a main support of vegetable

and animal life, and is still susceptible of running again and again

the same round, as circumstances may determine; so that, for aught we

can see to the contrary, the same identical atom may lie concealed for

thousands of centuries in a limestone rock; may at length be quarried,

set free in the limekiln, mix with the air, be absorbed from it by

plants, and, in succession, become a part of the frames of myriads of

living beings, till some concurrence of events consigns it once more to

a long repose, which, however, no way unfits it from again resuming its

former activity.

(32.) Now, this absolute indestructibility of the ultimate materials

of the world, in periods commensurate to our experience, and their

obstinate retention of the same properties, under whatever variety of

circumstances we choose to place them, however violent and seemingly

contradictory to their natures, is, of itself, enough to render it

highly improbable that time alone should have any influence over

them. All that age or decay can do seems to be included in a wasting

of parts which are only dissipated, not destroyed, or in a change of

sensible properties, which chemistry demonstrates to arise only from

new combinations of the same ingredients. But, after all, the question

is one entirely of experience: we cannot be sure, _à priori_, that

the laws of nature are _immutable_; but we can ascertain, by enquiry,

_whether they change or not_; and to this enquiry all experience

answers in the negative. It is not, of course, intended here to

deny that great operations, productive of extensive changes in the

visible state of nature,--such as, for instance, those contemplated

by the geologists, and embracing for their completion vast periods

of time,--are constantly going on; but these are consequences and

fulfilments of the laws of nature, not contradictions or exceptions

to them. No theorist regards such changes as alterations in the

fundamental principles of nature; he only endeavours to reconcile them,

and show how they result from laws already known, and judges of the

correctness of his theory by their ultimate agreement.

(33.) But the laws of nature are not only permanent, but consistent,

intelligible, and discoverable with such a moderate degree of

research, as is calculated rather to stimulate than to weary curiosity.

If we were set down, as creatures of another world, in any existing

society of mankind, and began to speculate on their actions, we should

find it difficult at first to ascertain whether they were subject to

any laws at all: but when, by degrees, we had found out that they did

consider themselves to be so; and would then proceed to ascertain, from

their conduct and its consequences, what these laws were, and in what

spirit conceived; though we might not perhaps have much difficulty

in discovering single rules applicable to particular cases, yet, the

moment we came to generalize, and endeavour from these to ascend, step

by step, and discover any steady pervading principle, the mass of

incongruities, absurdities, and contradictions, we should encounter,

would either dishearten us from further enquiry or satisfy us that what

we were in search of did not exist. It is quite the contrary in nature;

there we find no contradictions, no incongruities, but all is harmony.

What once is learnt we never have to unlearn. As rules advance in

generality, apparent exceptions become regular; and equivoque, in her

sublime legislation, is as unheard of as maladministration.

(34.) Living, then, in a world where such laws obtain, and under their

immediate dominion, it is manifestly of the utmost importance to know

them, were it for no other reason than to be sure, in all we undertake,

to have, at least, the law on our side, so as not to struggle in vain

against some insuperable difficulty opposed to us by natural causes.

What pains and expense would not the alchemists, for instance, have

been spared by a knowledge of those simple laws of composition and

decomposition, which now preclude all idea of the attainment of their

declared object! what an amount of ingenuity, thrown away on the

pursuit of the perpetual motion, might have been turned to better

use, if the simplest laws of mechanics had been known and attended to

by the inventors of innumerable contrivances destined to that end!

What tortures, inflicted on patients by imaginary cures of incurable

diseases, might have been dispensed with, had a few simple principles

of physiology been earlier recognised!

(35.) But if the laws of nature, on the one hand, are invincible

opponents, on the other, they are irresistible auxiliaries; and it

will not be amiss if we regard them in each of those characters, and

consider the great importance of a knowledge of them to mankind,--

I. _In showing us how to avoid attempting impossibilities._

II. _In securing us from important mistakes in attempting what

is, in itself, possible, by means either inadequate, or

actually opposed, to the end in view._

III. _In enabling us to accomplish our ends in the easiest,

shortest, most economical, and most effectual manner._

IV. _In inducing us to attempt, and enabling us to accomplish,

objects which, but for such knowledge, we should never have

thought of undertaking._

We shall therefore proceed to illustrate by examples the effect of

physical knowledge under each of these heads:--

(36.) Ex. 1. (35.) I. It is not many years since an attempt was made

to establish a colliery at Bexhill, in Sussex. The appearance of

thin seams and sheets of fossil-wood and wood-coal, with some other

indications similar to what occur in the neighbourhood of the great

coal-beds in the north of England, having led to the sinking of a

shaft, and the erection of machinery on a scale of vast expense, not

less than eighty thousand pounds are said to have been laid out on

this project, which, it is almost needless to add, proved completely

abortive, as every geologist would have at once declared it must, the

whole assemblage of geological facts being adverse to the existence

of a regular coal-bed _in_ the Hastings’ _sand_; while this, on which

Bexhill is situated, is separated from the _coal-strata_ by a series

of interposed beds of such enormous thickness as to render all idea of

penetrating _through_ them absurd. The history of mining operations

is full of similar cases, where a very moderate acquaintance with the

_usual order of nature_, to say nothing of theoretical views, would

have saved many a sanguine adventurer from utter ruin.

(37.) Ex. 2. (35.) II. The smelting of iron requires the application

of the most violent heat that can be raised, and is commonly performed

in tall furnaces, urged by great iron bellows driven by steam-engines.

Instead of employing this power to force _air_ into the furnace through

the intervention of bellows, it was, on one occasion, attempted to

employ the steam itself in, apparently, a much less circuitous manner;

viz. by directing the current of steam in a violent blast, from the

boiler at once into the fire. From one of the known ingredients of

steam being a highly inflammable body, and the other that essential

part of the air which supports combustion, it was imagined that this

would have the effect of increasing the fire to tenfold fury, whereas

it simply _blew it out_; a result which a slight consideration of the

laws of chemical combination, and the state in which the ingredient

elements exist in steam, would have enabled any one to predict without

a trial.

(38.) Ex. 3. (35.) II. After the invention of the diving-bell, and its

success in subaqueous processes, it was considered highly desirable

to devise some means of remaining for any length of time under water,

and rising at pleasure without assistance, so as either to examine,

at leisure, the bottom, or perform, at ease, any work that might be

required. Some years ago, an ingenious individual proposed a project

by which this end was to be accomplished. It consisted in sinking

the hull of a ship made quite water-tight, with the decks and sides

strongly supported by shores, and the only entry secured by a stout

trap-door, in such a manner, that by disengaging, from within, the

weights employed to sink it, it might rise of itself to the surface. To

render the trial more satisfactory, and the result more striking, the

projector himself made the first essay. It was agreed that he should

sink in twenty fathoms water, and rise again without assistance at

the expiration of twenty-four hours. Accordingly, making all secure,

fastening down his trap-door, and provided with all necessaries, as

well as with the means of making signals to indicate his situation,

this unhappy victim of his own ingenuity entered and was sunk. No

signal was made, and the time appointed elapsed. An immense concourse

of people had assembled to witness his rising, but in vain; for the

vessel was never seen more. The pressure of the water at so great a

depth had, no doubt, been completely under-estimated, and the sides of

the vessel being at once crushed in, the unfortunate projector perished

before he could even make the signal concerted to indicate his distress.

(39.) Ex. 4. (35.) III. In the granite quarries near Seringapatam the

most enormous blocks are separated from the solid rock by the following

neat and simple process. The workman having found a portion of the rock

sufficiently extensive, and situated near the edge of the part already

quarried, lays bare the upper surface, and marks on it a line in the

direction of the intended separation, along which a groove is cut with

a chisel about a couple of inches in depth. Above this groove a narrow

line of fire is then kindled, and maintained till the rock below is

thoroughly heated, immediately on which a line of men and women, each

provided with a pot full of cold water, suddenly sweep off the ashes,

and pour the water into the heated groove, when the rock at once

splits with a clean fracture. Square blocks of six feet in the side,

and upwards of eighty feet in length, are sometimes detached by this

method, or by another equally simple and efficacious, but not easily

explained without entering into particulars of mineralogical detail.[11]

(40.) Ex. 5. (35.) III. Hardly less simple and efficacious is the

process used in some parts of France, where mill-stones are made. When

a mass of stone sufficiently large is found, it is cut into a cylinder

several feet high, and the question then arises how to subdivide

this into horizontal pieces so as to make as many mill-stones. For

this purpose horizontal indentations or grooves are chiselled out

quite round the cylinder, at distances corresponding to the thickness

intended to be given to the mill-stones, into which wedges of dried

wood are driven. These are then wetted, or exposed to the night dew,

and next morning the different pieces are found separated from each

other by the expansion of the wood, consequent on its absorption of

moisture; an irresistible natural power thus accomplishing, almost

without any trouble, and at no expense, an operation which, from

the peculiar hardness and texture of the stone, would otherwise

be impracticable but by the most powerful machinery or the most

persevering labour.

(41.) Ex. 6. (35.) III. To accomplish our ends quickly is often of, at

least, as much importance as to accomplish them with little labour and

expense. There are innumerable processes which, if left to themselves,

_i. e._ to the ordinary operation of natural causes, are done, and well

done, but with extreme slowness, and in such cases it is often of

the highest practical importance to accelerate them. The bleaching of

linen, for instance, performed in the natural way by exposure to sun,

rain, and wind, requires many weeks or even months for its completion;

whereas, by the simple immersion of the cloth in a liquid, chemically

prepared, the same effect is produced in a few hours. The whole circle

of the arts, indeed, is nothing but one continued comment upon this

head of our subject. The instances above given are selected, not on

account of their superior importance, but for the simplicity and

_directness_ of application of the principles on which they depend, to

the objects intended to be attained.

(42.) But so constituted is the mind of man, that his views enlarge,

and his desires and wants increase, in the full proportion of the

facilities afforded to their gratification, and, indeed, with augmented

rapidity, so that no sooner has the successful exercise of his powers

accomplished any considerable simplification or improvement of

processes subservient to his use or comfort, than his faculties are

again on the stretch to extend the limits of his newly acquired power;

and having once experienced the advantages which are to be gathered

by availing himself of some of the powers of nature to accomplish

his ends, he is led thenceforward to regard them all as a treasure

placed at his disposal, if he have only the art, the industry, or the

good fortune, to penetrate those recesses which conceal them from

immediate view. Having once learned to look on knowledge as power, and

to avail himself of it as such, he is no longer content to limit his

enterprises to the beaten track of former usage, but is constantly

led onwards to contemplate objects which, in a previous stage of his

progress, he would have regarded as unattainable and visionary, had he

even thought of them at all. It is here that the investigation of the

hidden powers of nature becomes a mine, every vein of which is pregnant

with inexhaustible wealth, and whose ramifications appear to extend in

all directions wherever human wants or curiosity may lead us to explore.

(43.) Between the physical sciences and the arts of life there subsists

a constant mutual interchange of good offices, and no considerable

progress can be made in the one without of necessity giving rise to

corresponding steps in the other. On the one hand, every art is in

some measure, and many entirely, dependent on those very powers and

qualities of the material world which it is the object of physical

enquiry to investigate and explain; and, accordingly, abundant examples

might be cited of cases where the remarks of experienced artists, or

even ordinary workmen, have led to the discovery of natural qualities,

elements, or combinations which have proved of the highest importance

in physics. Thus (to give an instance), a soap-manufacturer remarks

that the residuum of his ley, when exhausted of the alkali for which

he employs it, produces a corrosion of his copper boiler for which he

cannot account. He puts it into the hands of a scientific chemist for

analysis, and the result is the discovery of one of the most singular

and important chemical elements, iodine. The properties of this,

being studied, are found to occur most appositely in illustration

and support of a variety of new, curious, and instructive views then

gaining ground in chemistry, and thus exercise a marked influence

over the whole body of that science. Curiosity is excited: the origin

of the new substance is traced to the sea-plants from whose ashes

the principal ingredient of soap is obtained, and ultimately to the

sea-water itself. It is thence hunted through nature, discovered in

salt mines and springs, and pursued into all bodies which have a marine

origin; among the rest, into sponge. A medical practitioner[12] then

calls to mind a reputed remedy for the cure of one of the most grievous

and unsightly disorders to which the human species is subject--the

_goître_--which infests the inhabitants of mountainous districts to

an extent that in this favoured land we have happily no experience

of, and which was said to have been originally cured by the ashes of

burnt sponge. Led by this indication he tries the effect of iodine on

that complaint, and the result establishes the extraordinary fact that

this singular substance, taken as a medicine, acts with the utmost

promptitude and energy on _goître_, dissipating the largest and most

inveterate in a short time, and acting (of course, like all medicines,

even the most approved, with occasional failures,) as a specific, or

natural antagonist, against that odious deformity. It is thus that

any accession to our knowledge of nature is sure, sooner or later, to

make itself felt in some practical application, and that a benefit

conferred on science by the casual observation or shrewd remark of even

an unscientific or illiterate person infallibly repays itself with

interest, though often in a way that could never have been at first

contemplated.

(44.) It is to such observation, reflected upon, however, and matured

into a rational and scientific form by a mind deeply imbued with the

best principles of sound philosophy, that we owe the practice of

vaccination; a practice which has effectually subdued, in every country

where it has been introduced, one of the most frightful scourges of

the human race, and in some extirpated it altogether. Happily for us

we know only by tradition the ravages of the small-pox, as it existed

among us hardly more than a century ago, and as it would in a few

years infallibly exist again, were the barriers which this practice,

and that of inoculation, oppose to its progress abandoned. Hardly

inferior to this terrible scourge on land was, within the last seventy

or eighty years, the scurvy at sea. The sufferings and destruction

produced by this horrid disorder on board our ships when, as a matter

of course, it broke out after a few months’ voyage, seem now almost

incredible. Deaths to the amount of eight or ten a day in a moderate

ship’s company; bodies sewn up in hammocks and washing about the decks

for want of strength and spirits on the part of the miserable survivors

to cast them overboard; and every form of loathsome and excruciating

misery of which the human frame is susceptible:--such are the pictures

which the narratives of nautical adventure in those days continually

offer.[13] At present the scurvy is almost completely eradicated in

the navy, partly, no doubt, from increased and increasing attention to

general cleanliness, comfort, and diet; but mainly from the constant

use of a simple and palatable preventive, the acid of the lemon,

served out in daily rations. If the gratitude of mankind be allowed on

all hands to be the just meed of the philosophic physician, to whose

discernment in seizing, and perseverance in forcing it on public notice

we owe the great safeguard of infant life, it ought not to be denied to

those[14] whose skill and discrimination have thus strengthened the

sinews of our most powerful arm, and obliterated one of the darkest

features in the most glorious of all professions.

(45.) These last, however, are instances of simple observation,

limited to the point immediately in view, and assuming only so far the

character of science as a systematic adoption of good and rejection of

evil, when grounded on experience carefully weighed, justly entitle

it to do. They are not on that account less appositely cited as

instances of the importance of a knowledge of nature and its laws to

our well-being; though, like the great inventions of the mariner’s

compass and of gunpowder, they may have stood, in their origin,

unconnected with more general views. They are rather to be looked upon

as the spontaneous produce of a territory essentially fertile, than as

forming part of the succession of harvests which the same bountiful

soil, diligently cultivated, is capable of yielding. The history of

iodine above related affords, however, a perfect specimen of the

manner in which a knowledge of natural properties and laws, collected

from facts having no reference to the object to which they have

been subsequently applied, enables us to set in array the resources

of nature against herself; and deliberately, of afore-thought, to

devise remedies against the dangers and inconveniences which beset

us. In this view we might instance, too, the _conductor_, which, in

countries where thunder-storms are more frequent and violent than in

our own, and at sea (where they are attended with peculiar danger,

both from the greater probability of accident, and its more terrible

consequences when it does occur,) forms a most real and efficient

preservative against the effects of lightning[15]:--the _safety-lamp_,

which enables us to walk with light and security while surrounded with

an atmosphere more explosive than gunpowder:--the _life-boat_, which

cannot be sunk, and which offers relief in circumstances of all others

the most distressing to humanity, and of which a recent invention

promises to extend the principle to ships of the largest class:--the

_lighthouse_, with the capital improvements which the lenses of

Brewster and Fresnel, and the elegant lamp of lieutenant Drummond, have

conferred, and promise yet to confer by their wonderful powers, the one

of producing the most intense light yet known, the others of conveying

it undispersed to great distances:--the discovery of the disinfectant

powers of chlorine, and its application to the destruction of miasma

and contagion:--that of _quinine_, the essential principle in which

reside the febrifuge qualities of the Peruvian bark, a discovery by

which posterity is yet to benefit in its full extent, but which has

already begun to diffuse _comparative_ comfort and health through

regions almost desolated by pestiferous exhalations[16];--and, if we

desist, it is not because the list is exhausted, but because a sample,

not a catalogue, is intended.

(46.) One instance more, however, we will add, to illustrate the

manner in which a most familiar effect, which seemed destined only

to amuse children, or, at best, to furnish a philosophic toy, may

become a safeguard of human life, and a remedy for a most serious

and distressing evil. In needle manufactories the workmen who point

the needles are constantly exposed to excessively minute particles of

steel which fly from the grindstones, and mix, though imperceptible

to the eye, as the finest dust in the air, and are inhaled with their

breath. The effect, though imperceptible on a short exposure, yet,

being constantly repeated from day to day, produces a constitutional

irritation dependent on the tonic properties of the steel, which is

sure to terminate in pulmonary consumption; insomuch, that persons

employed in this kind of work used scarcely ever to attain the age of

forty years.[17] In vain was it attempted to purify the air before its

entry into the lungs by gauzes or linen guards; the dust was too fine

and penetrating to be obstructed by such coarse expedients, till some

ingenious person bethought him of that wonderful power which every

child who searches for its mother’s needle with a magnet, or admires

the motions and arrangement of a few steel filings on a sheet of paper

held above it, sees in exercise. Masks of magnetized steel wire are now

constructed and adapted to the faces of the workmen. By these the air

is not merely _strained_ but _searched_ in its passage through them,

and each obnoxious atom arrested and removed.

(47.) Perhaps there is no result which places in a stronger light the

advantages which are to be derived from a mere knowledge of the _usual

order of nature_, without any attempt on our part to modify it, and

apart from all consideration of its causes, than the institution of

life-assurances. Nothing is more uncertain than the life of a single

individual; and it is the sense of this insecurity which has given

rise to such institutions. They are, in their nature and objects,

the precise reverse of gambling speculations, their object being to

equalize vicissitude, and to place the pecuniary relations of numerous

masses of mankind, in so far as they extend, on a footing independent

of individual casualty. To do this with the greatest possible

advantage, or indeed with any advantage at all, it is necessary to know

the _laws of mortality_, or the average numbers of individuals, out

of a great multitude, who die at every period of life from infancy to

extreme old age. At first sight this would seem a hopeless enquiry; to

some, perhaps, a presumptuous one. But it has been made; and the result

is, that, abating extraordinary causes, such as wars, pestilence, and

the like, a remarkable regularity _does_ obtain, quite sufficient

to afford grounds not only for general estimations, but for nice

calculations of risk and adventure, such as infallibly to insure the

success of any such institution founded on good computations; and thus

to confer such stability on the fortunes of families dependent on the

exertions of one individual as to constitute an important feature in

modern civilization. The only thing to be feared in such institutions

is their too great multiplication and consequent competition, by which

a spirit of gambling and underbidding is liable to be generated among

their conductors, and the very mischief may be produced, on a scale of

frightful extent, which they are especially intended to prevent.

(48.) We have hitherto considered only cases in which a knowledge of

natural laws enables us to improve our condition, by counteracting

evils of which, but for its possession, we must have remained forever

the helpless victims. Let us now take a similar view of those in which

we are enabled to call in nature as an auxiliary to augment our actual

power, and capacitate us for undertakings, which without such aid might

seem to be hopeless. Now, to this end, it is necessary that we should

form a just conception of what those hidden powers of nature _are_,

which we can at pleasure call into action;--how far they transcend

the measure of human force, and set at naught the efforts not only of

individuals but of whole nations of men.

(49.) It is well known to modern engineers, that _there is virtue_ in a

bushel of coals properly consumed, to raise seventy millions of pounds

weight a foot high. This is actually the _average_ effect of an engine

at this moment working in Cornwall.[18] Let us pause a moment, and

consider what this is equivalent to in matters of practice.

(50.) The ascent of Mont Blanc from the valley of Chamouni is

considered, and with justice, as the most toilsome feat that a strong

man can execute in two days. The combustion of two pounds of coal would

place him on the summit.[19]

(51.) The Menai Bridge, one of the most stupendous works of art that

has been raised by man in modern ages, consists of a mass of iron, not

less than four millions of pounds in weight, suspended at a medium

height of about 120 feet above the sea. The consumption of seven

bushels of coal would suffice to raise it to the place where it hangs.

(52.) The great pyramid of Egypt is composed of granite. It is 700 feet

in the side of its base, and 500 in perpendicular height, and stands on

eleven acres of ground. Its weight is, therefore, 12,760 millions of

pounds, at a medium height of 125 feet; consequently it would be raised

by the effort of about 630 chaldrons of coal, a quantity consumed in

some founderies in a week.

(53.) The annual consumption of coal in London is estimated at

1,500,000 chaldrons. The effort of this quantity would suffice to raise

a cubical block of marble, 2200 feet in the side, through a space equal

to its own height, or to pile one such mountain upon another. The Monte

Nuovo, near Pozzuoli, (which was erupted in a single night by volcanic

fire,) might have been raised by such an effort, from a depth of 40,000

feet, or about eight miles.

(54.) It will be observed, that, in the above statement, the inherent

power of fuel is, of necessity, greatly under-rated. It is not

pretended by engineers that the economy of fuel is yet pushed to its

utmost limit, or that the whole effective power is obtained in any

application of fire yet devised; so that were we to say 100 millions

instead of 70, we should probably be nearer the truth.

(55.) The powers of wind and water, which we are constantly impressing

into our service, can scarcely be called latent or hidden, yet it

is not fully considered, in general, what they _do_ effect for us.

Those who would judge of what advantage may be taken of the wind, for

example, even on land (not to speak of navigation), may turn their

eyes on Holland. A great portion of the most valuable and populous

tract of this country lies much below the level of the sea, and is only

preserved from inundation by the maintenance of embankments. Though

these suffice to keep out the abrupt influx of the ocean, they cannot

oppose that law of nature, by which fluids, in seeking their level,

insinuate themselves through the pores and subterraneous channels

of a loose sandy soil, and keep the country in a constant state of

infiltration from below upwards. To counteract this tendency, as well

as to get rid of the rain water, which has no natural outlet, pumps

worked by windmills are established in great numbers, on the dams

and embankments, which pour out the water, as from a leaky ship, and

in effect preserve the country from submersion, by taking advantage

of every wind that blows. To drain the Haarlem lake[20] would seem a

hopeless project to any speculators but those who had the steam-engine

at their command, or had learnt in Holland what might be accomplished

by the constant agency of the desultory but unwearied powers of wind.

But the Dutch engineer measures his surface, calculates the number of

his pumps, and, trusting to time and his experience of the operation of

the winds for the success of his undertaking, boldly forms his plans to

lay dry the bed of an inland sea, of which those who stand on one shore

cannot see the other.[21]

(56.) To gunpowder, as a source of mechanical power, it seems hardly

necessary to call attention; yet it is only when we endeavour to

_confine_ it, that we get a full conception of the immense energy of

that astonishing agent. In count Rumford’s experiments, twenty-eight

grains of powder confined in a cylindrical space, _which it just

filled_, tore asunder a piece of iron which would have resisted

a strain of 400,000 lbs.[22], applied at no greater mechanical

disadvantage.

(57.) But chemistry furnishes us with means of calling into sudden

action forces of a character infinitely more tremendous than that

of gunpowder. The terrific violence of the different fulminating

compositions is such, that they can only be compared to those

untameable animals, whose ferocious strength has hitherto defied all

useful management, or rather to spirits evoked by the spells of a

magician, manifesting a destructive and unapproachable power, which

makes him but too happy to close his book, and break his wand, as the

price of escaping: unhurt from the storm he has raised. Such powers are

not yet subdued to our purposes, whatever they may hereafter be; but,

in the expansive force of gases, liberated slowly and manageably from

chemical mixtures, we have a host of inferior, yet still most powerful,

energies, capable of being employed in a variety of useful ways,

according to emergencies.[23]

(58.) Such are the forces which nature lends us for the accomplishment

of our purposes, and which it is the province of practical Mechanics to

teach us to combine and apply in the most advantageous manner; without

which the mere command of power would amount to nothing. Practical

Mechanics is, in the most pre-eminent sense, a _scientific art_; and

it may be truly asserted, that almost all the great combinations of

modern mechanism, and many of its refinements and nicer improvements,

are creations of pure intellect, grounding its exertion upon a moderate

number of very elementary propositions in theoretical mechanics and

geometry. On this head we might dwell long, and find ample matter,

both for reflection and wonder; but it would require not volumes

merely, but libraries, to enumerate and describe the prodigies of

ingenuity which have been lavished on every thing connected with

machinery and engineering. By these it is that we are enabled to

diffuse over the whole earth the productions of any part of it; to fill

every corner of it with miracles of art and labour, in exchange for its

peculiar commodities; and to concentrate around us, in our dwellings,

apparel and utensils, the skill and workmanship not of a few expert

individuals, but of all who, in the present and past generations, have

contributed their improvements to the processes of our manufactures.

(59.) The transformations of chemistry, by which we are enabled to

convert the most apparently useless materials into important objects

in the arts, are opening up to us every day sources of wealth and

convenience of which former ages had no idea, and which have been

pure gifts of science to man. Every department of art has felt their

influence, and new instances are continually starting forth of the

unlimited resources which this wonderful science developes in the

most sterile parts of nature. Not to mention the impulse which its

progress has given to a host of other sciences, which will come more

particularly under consideration in another part of this discourse,

what strange and unexpected results has it not brought to light in its

application to some of the most common objects! Who, for instance,

would have conceived that linen rags were capable of producing _more

than their own weight_ of sugar, by the simple agency of one of the

cheapest and most abundant acids?[24]--that dry bones could be a

magazine of nutriment, capable of preservation for years, and ready to

yield up their sustenance in the form best adapted to the support of

life, on the application of that powerful agent, steam, which enters

so largely into all our processes, or of an acid at once cheap and

durable?[25]--that sawdust itself is susceptible of conversion into

a substance bearing no remote analogy to bread; and though certainly

less palatable than that of flour, yet no way disagreeable, and

both wholesome and digestible as well as highly nutritive?[26] What

economy, in all processes where chemical agents are employed, is

introduced by the exact knowledge of the proportions in which natural

elements unite, and their mutual powers of displacing each other! What

perfection in all the arts where fire is employed, either in its more

violent applications, (as, for instance, in the smelting of metals by

the introduction of well adapted fluxes, whereby we obtain the whole

produce of the ore in its purest state,) or in its milder forms, as

in sugar-refining (the whole modern practice of which depends on a

curious and delicate remark of a late eminent scientific chemist on the

nice adjustment of temperature at which the crystallization of syrup

takes place); and a thousand other arts which it would be tedious to

enumerate!

(60.) Armed with such powers and resources, it is no wonder if the

enterprise of man should lead him to form and execute projects

which, to one uninformed of their grounds, would seem altogether

disproportionate. Were they to have been proposed at once, we should,

no doubt, have rejected them as such: but developed, as they have been,

in the slow succession of ages, they have only taught us that things

regarded impossible in one generation may become easy in the next; and

that the power of man over nature is limited only by the one condition,

that it must be exercised in conformity with the laws of nature. He

must study those laws as he would the disposition of a horse he would

ride, or the character of a nation he would govern; and the moment he

presumes either to thwart her fundamental rules, or ventures to measure

his strength with hers, he is at once rendered severely sensible of

his imbecility, and meets the deserved punishment of his rashness and

folly. But if, on the other hand, he will consent to use, without

abusing, the resources thus abundantly placed at his disposal, and obey

that he may command, there seems scarcely any conceivable limit to the

degree in which the _average_ physical condition of great masses of

mankind may be improved, their wants supplied, and their conveniences

and comforts increased. Without adopting such an exaggerated view,

as to assert that the meanest inhabitant of a civilized society is

superior in physical condition to the lordly savage, whose energy and

uncultivated ability gives him a natural predominance over his fellow

denizens of the forest,--at least, if we compare like with like, and

consider the multitude of human beings who are enabled, in an advanced

state of society, to subsist in a degree of comfort and abundance,

which at best only a few of the most fortunate in a less civilized

state could command, we shall not be at a loss to perceive the

principle on which we ought to rest our estimate of the advantages of

civilization; and which applies with hardly less force to every degree

of it, when contrasted with that next inferior, than to the broad

distinction between civilized and barbarous life in general.

(61.) The difference of the degrees in which the individuals of a great

community enjoy the good things of life has been a theme of declamation

and discontent in all ages; and it is doubtless our paramount duty, in

every state of society, to alleviate the pressure of the purely evil

part of this distribution as much as possible, and, by all the means

we can devise, secure the lower links in the chain of society from

dragging in dishonour and wretchedness: but there is a point of view

in which the picture is at least materially altered in its expression.

In comparing society on its present immense scale, with its infant

or less developed state, we must at least take care to enlarge every

feature in the same proportion. If, on comparing the _very_ lowest

states in civilized and savage life, we admit a difficulty in deciding

to which the preference is due, at least in every superior grade we

cannot hesitate a moment; and if we institute a similar comparison in

every different stage of its progress, we cannot fail to be struck with

the rapid _rate of dilatation_ which every degree upward of the scale,

so to speak, exhibits, and which, in an estimate of averages, gives

an immense preponderance to the present over every former condition

of mankind, and, for aught we can see to the contrary, will place

succeeding generations in the same degree of superior relation to the

present that this holds to those passed away. Or we may put the same

proposition in other words, and, admitting the existence of every

inferior grade of advantage in a higher state of civilization which

subsisted in the preceding, we shall find, first, that, taking state

for state, the proportional numbers of those who enjoy the higher

degrees of advantage increases with a constantly accelerated rapidity

as society advances; and, secondly, that the superior extremity of

the scale is constantly enlarging by the addition of new degrees. The

condition of a European prince is now as far superior, in the command

of real comforts and conveniences, to that of one in the middle ages,

as that to the condition of one of his own dependants.

(62.) The advantages conferred by the augmentation of our physical

resources through the medium of increased knowledge and improved art

have this peculiar and remarkable property,--that they are in their

nature diffusive, and cannot be enjoyed in any exclusive manner by a

few. An eastern despot may extort the riches and monopolize the art

of his subjects for his own personal use; he may spread around him an

unnatural splendour and luxury, and stand in strange and preposterous

contrast with the general penury and discomfort of his people; he may

glitter in jewels of gold and raiment of needlework; but the wonders

of well contrived and executed manufacture which we use daily, and

the comforts which have been invented, tried, and improved upon by

thousands, in every form of domestic convenience, and for every

ordinary purpose of life, can never be enjoyed by him. To produce a

state of things in which the physical advantages of civilized life

can exist in a high degree, the stimulus of increasing comforts and

constantly elevated desires, must have been felt by millions; since it

is not in the power of a few individuals to create that wide demand

for useful and ingenious applications, which alone can lead to great

and rapid improvements, unless backed by that arising from the speedy

diffusion of the same advantages among the mass of mankind.

(63.) If this be true of physical advantages, it applies with still

greater force to intellectual. Knowledge can neither be adequately

cultivated nor adequately enjoyed by a few; and although the conditions

of our existence on earth may be such as to preclude an abundant

supply of the physical necessities of all who may be born, there

is no such law of nature in force against that of our intellectual

and moral wants. Knowledge is not, like food, destroyed by use, but

rather augmented and perfected. It acquires not, perhaps, a greater

certainty, but at least a confirmed authority and a probable duration,

by universal assent; and there is no body of knowledge so complete,

but that it may acquire accession, or so free from error but that it

may receive correction in passing through the minds of millions. Those

who admire and love knowledge for its own sake ought to wish to see

its elements made accessible to all, were it only that they may be

the more thoroughly examined into, and more effectually developed in

their consequences, and receive that ductility and plastic quality

which the pressure of minds of all descriptions, constantly moulding

them to their purposes, can alone bestow. But to this end it is

necessary that it should be divested, as far as possible, of artificial

difficulties, and stripped of all such technicalities as tend to place

it in the light of a craft and a mystery, inaccessible without a kind

of apprenticeship. Science, of course, like every thing else, has its

own peculiar terms, and, so to speak, its idioms of language; and these

it would be unwise, were it even possible, to relinquish: but every

thing that tends to clothe it in a strange and repulsive garb, and

especially every thing that, to keep up an appearance of superiority

in its professors over the rest of mankind, assumes an unnecessary

guise of profundity and obscurity, should be sacrificed without mercy.

Not to do this, is to deliberately reject the light which the natural

unencumbered good sense of mankind is capable of throwing on every

subject, even in the elucidation of principles: but where principles

are to be applied to practical uses it becomes absolutely necessary;

as all mankind have then an interest in their being so familiarly

understood, that no mistakes shall arise in their application.

(64.) The same remark applies to arts. They cannot be perfected till

their whole processes are laid open, and their language simplified and

rendered universally intelligible. Art is the application of knowledge

to a practical end. If the knowledge be merely accumulated experience,

the art is _empirical_; but if it be experience reasoned upon and

brought under general principles, it assumes a higher character, and

becomes a _scientific art_. In the progress of mankind from barbarism

to civilised life, the arts necessarily precede science. The wants and

cravings of our animal constitution must be satisfied; the comforts,

and some of the luxuries, of life must exist. Something must be given

to the vanity of show, and more to the pride of power: the round of

baser pleasures must have been tried and found insufficient, before

intellectual ones can gain a footing; and when they have obtained it,

the delights of poetry and its sister arts still take precedence of

contemplative enjoyments, and the severer pursuits of thought; and

when these in time begin to charm from their novelty, and sciences

begin to arise, they will at first be those of pure speculation. The

mind delights to escape from the trammels which had bound it to earth,

and luxuriates in its newly found powers. Hence, the abstractions of

geometry--the properties of numbers--the movements of the celestial

spheres--whatever is abstruse, remote, and extramundane--become the

first objects of infant science. Applications come late: the arts

continue slowly progressive, but their realm remains separated from

that of science by a wide gulf which can only be passed by a powerful

spring. They form their own language and their own conventions, which

none but artists can understand. The whole tendency of empirical

art, is to bury itself in technicalities, and to place its pride in

particular short cuts and mysteries known only to adepts; to surprise

and astonish by results, but conceal processes. The character of

science is the direct contrary. It delights to lay itself open to

enquiry, and is not satisfied with its conclusions, till it can make

the road to them broad and beaten: and in its applications it preserves

the same character; its whole aim being to strip away all technical

mystery, to illuminate every dark recess, and to gain free access to

all processes, with a view to improve them on rational principles.

It would seem that a union of two qualities almost opposite to each

other--a going forth of the thoughts in two directions, and a sudden

transfer of ideas from a remote station in one to an equally distant

one in the other--is required to start the first idea of _applying

science_. Among the Greeks, this point was attained by Archimedes, but

attained too late, on the eve of that great eclipse of science which

was destined to continue for nearly eighteen centuries, till Galileo in

Italy, and Bacon in England, at once dispelled the darkness: the one,

by his inventions and discoveries; the other, by the irresistible force

of his arguments and eloquence.

(65.) Finally, the improvement effected in the condition of mankind

by advances in physical science as applied to the useful purposes of

life, is very far from being limited to their direct consequences in

the more abundant supply of our physical wants, and the increase of our

comforts. Great as these benefits are, they are yet but steps to others

of a still higher kind. The successful results of our experiments and

reasonings in natural philosophy, and the incalculable advantages which

experience, systematically consulted and dispassionately reasoned on,

has conferred in matters purely physical, tend of necessity to impress

something of the well weighed and progressive character of science on

the more complicated conduct of our social and moral relations. It

is thus that legislation and politics become gradually regarded as

experimental sciences; and history, not, as formerly, the mere record

of tyrannies and slaughters, which, by immortalizing the execrable

actions of one age, perpetuates the ambition of committing them in

every succeeding one, but as the archive of experiments, successful

and unsuccessful, gradually accumulating towards the solution of the

grand problem--how the advantages of government are to be secured

with the least possible inconvenience to the governed. The celebrated

apophthegm, that nations never profit by experience, becomes yearly

more and more untrue. Political economy, at least, is found to have

sound principles, founded in the moral and physical nature of man,

which, however lost sight of in particular measures--however even

temporarily controverted and borne down by clamour--have yet a stronger

and stronger testimony borne to them in each succeeding generation, by

which they must, sooner or later, prevail. The idea once conceived and

verified, that great and noble ends are to be achieved, by which the

condition of the whole human species shall be permanently bettered,

by bringing into exercise a sufficient quantity of sober thought, and

by a proper adaptation of means, is of itself sufficient to set us

earnestly on reflecting what ends _are_ truly great and noble, either

in themselves, or as conducive to others of a still loftier character;

because we are not now, as heretofore, hopeless of attaining them. It

is not now equally harmless and insignificant, whether we are right

or wrong; since we are no longer supinely and helplessly carried down

the stream of events, but feel ourselves capable of buffetting at

least with its waves, and perhaps of riding triumphantly over them:

for why should we despair that the reason which has enabled us to

subdue all nature to our purposes, should (if permitted and assisted

by the providence of God) achieve a far more difficult conquest; and

ultimately find some means of enabling the collective wisdom of mankind

to bear down those obstacles which individual short-sightedness,

selfishness, and passion, oppose to all improvements, and by which

the highest hopes are continually blighted, and the fairest prospects

marred.

PART II.

OF THE PRINCIPLES ON WHICH PHYSICAL SCIENCE RELIES FOR ITS

SUCCESSFUL PROSECUTION, AND THE RULES BY WHICH A SYSTEMATIC

EXAMINATION OF NATURE SHOULD BE CONDUCTED, WITH ILLUSTRATIONS OF

THEIR INFLUENCE AS EXEMPLIFIED IN THE HISTORY OF ITS PROGRESS.

CHAPTER I.

OF EXPERIENCE AS THE SOURCE OF OUR KNOWLEDGE.--OF THE DISMISSAL OF

PREJUDICES.--OF THE EVIDENCE OF OUR SENSES.

(66.) Into abstract science, as we have before observed, the notion of

cause does not enter. The truths it is conversant with are _necessary_

ones, and exist independent of cause. There may be no such real _thing_

as a right-lined triangle marked out in space; but the moment we

conceive one in our minds, we cannot refuse to admit the sum of its

three angles to be equal to two right angles; and if in addition we

conceive one of its angles to be a right angle, we cannot thenceforth

refuse to admit that the sum of the squares on the two sides, including

the right angle, is equal to the square on the side subtending it. To

maintain the contrary, would be, in effect, to deny its being right

angled. No one _causes_ or _makes_ all the diameters of an ellipse

to be bisected in its centre. To assert the contrary, would not be

to rebel against a power, but to deny our own words. But in natural

science _cause_ and _effect_ are the ultimate relations we contemplate;

and _laws_, whether imposed or maintained, which, for aught we can

perceive, might have been other than they are. This distinction is

very important. A clever man, shut up alone and allowed unlimited

time, might reason out for himself all the truths of mathematics, by

proceeding from those simple notions of space and number of which he

cannot divest himself without ceasing to think. But he could never

tell, by any effort of reasoning, what would become of a lump of sugar

if immersed in water, or what impression would be produced on his eye

by mixing the colours yellow and blue.

(67.) We have thus pointed out to us, as the great, and indeed only

ultimate source of our knowledge of nature and its laws, EXPERIENCE;

by which we mean, not the experience of one man only, or of one

generation, but the accumulated experience of all mankind in all ages,

registered in books or recorded by tradition. But experience may be

acquired in two ways: either, first, by noticing facts as they occur,

without any attempt to influence the frequency of their occurrence, or

to vary the circumstances under which they occur; this is OBSERVATION:

or, secondly, by putting in action causes and agents over which we

have control, and purposely varying their combinations, and noticing

what effects take place; this is EXPERIMENT. To these two sources we

must look as the fountains of all natural science. It is not intended,

however, by thus distinguishing observation from experiment, to

place them in any kind of contrast. Essentially they are much alike,

and differ rather in degree than in kind; so that, perhaps, the

terms _passive_ and _active observation_ might better express their

distinction; but it is, nevertheless, highly important to mark the

different states of mind in inquiries carried on by their respective

aids, as well as their different effects in promoting the progress of

science. In the former, we sit still and listen to a tale, told us,

perhaps obscurely, piecemeal, and at long intervals of time, with our

attention more or less awake. It is only by after-rumination that we

gather its full import; and often, when the opportunity is gone by, we

have to regret that our attention was not more particularly directed to

some point which, at the time, appeared of little moment, but of which

we at length appretiate the importance. In the latter, on the other

hand, we cross-examine our witness, and by comparing one part of his

evidence with the other, while he is yet before us, and reasoning upon

it in his presence, are enabled to put pointed and searching questions,

the answer to which may at once enable us to make up our minds.

Accordingly it has been found invariably, that in those departments

of physics where the phenomena are beyond our control, or into which

experimental enquiry, from other causes, has not been carried, the

progress of knowledge has been slow, uncertain, and irregular; while in

such as admit of experiment, and in which mankind have agreed to its

adoption, it has been rapid, sure, and steady. For example, in our

knowledge of the nature and causes of volcanoes, earthquakes, the fall

of stones from the sky, the appearance of new stars and disappearance

of old ones, and other of those great phenomena of nature which are

altogether beyond our command, and at the same time are of too rare

occurrence to permit any one to repeat and rectify his impressions

respecting them, we know little more now than in the earliest times.

Here our tale is told us slowly, and in broken sentences. In astronomy,

again, we have at least an uninterrupted narrative; the opportunity

of observation is constantly present, and makes up in some measure

for the impossibility of varying our point of view, and calling for

information at the precise moment it is wanted. Accordingly, astronomy,

regarded as a science of mere observation, arrived, though by very

slow degrees, to a state of considerable maturity. But the moment that

it became a branch of mechanics, a science essentially experimental,

(that is to say, one in which any principle laid down can be subjected

to immediate and decisive _trial_, and where experience does not

require to be waited for,) its progress suddenly acquired a tenfold

acceleration; nay, to such a degree, that it has been asserted, and

we believe with truth, that were the records of all observations from

the earliest ages annihilated, leaving only those made in a single

observatory[27], during a single lifetime[28], the whole of this most

perfect of sciences might, from those data, and as to the objects

included in them, be at once reconstructed, and appear precisely as

it stood at their conclusion. To take another instance: mineralogy,

till modern times, could hardly be said to exist. The description

of even the precious stones in Theophrastus and Pliny are, in most

cases, hardly sufficient to identify them, and in many fall short

even of that humble object; more recent observers, by attending more

carefully to the obvious characters of minerals, had formed a pretty

extensive catalogue of them, and made various attempts to arrange and

methodize the knowledge thus acquired, and even to deduce some general

conclusions respecting the forms they habitually assume: but from the

moment that chemical analysis was applied to resolve them into their

constituent elements, and that, led by a happy accident, the genius

of Bergmann discovered the general fact, that they could be _cloven_

or split in such directions as to lay bare their peculiar primitive

or fundamental forms, (which lay concealed within them, as the statue

might be conceived encrusted in its marble envelope,)--from that

moment, mineralogy ceased to be an unmeaning list of names, a mere

laborious cataloguing of stones and rubbish, and became, what it now

is, a regular, methodical, and most important science, in which every

year is bringing to light new relations, new laws, and new practical

applications.

(68.) Experience once recognized as the fountain of all our knowledge

of nature, it follows that, in the study of nature and its laws, we

ought at once to make up our minds to dismiss as idle prejudices, or

at least suspend as premature, any preconceived notion of what might

or what ought to be the order of nature in any proposed case, and

content ourselves with observing, as a plain matter of fact, what _is_.

To experience we refer, as the only ground of all physical enquiry.

But before experience itself can be used with advantage, there is one

preliminary step to make, which depends wholly on ourselves: it is

the absolute dismissal and clearing the mind of all prejudice, from

whatever source arising, and the determination to stand and fall by

the result of a direct appeal to facts in the first instance, and of

strict logical deduction from them afterwards. Now, it is necessary

to distinguish between two kinds of prejudices, which exercise very

different dominion over the mind, and, moreover, differ extremely

in the difficulty of dispossessing them, and the process to be gone

through for that purpose. These are,--

1. Prejudices of opinion.

2. Prejudices of sense.

(69.) By prejudices of opinion, we mean opinions hastily taken up,

either from the assertion of others, from our own superficial views,

or from vulgar observation, and which, from being constantly admitted

without dispute, have obtained the strong hold of habit on our minds.

Such were the opinions once maintained that the earth is the greatest

body in the universe, and placed immovable in its centre, and all the

rest of the universe created for its sole use; that it is the nature

of fire and of sounds to ascend; that the moonlight is cold; that dews

_fall_ from the air, &c.

(70.) To combat and destroy such prejudices we may proceed in two ways,

either by demonstrating the falsehood of the facts alleged in their

support, or by showing how the appearances, which seem to countenance

them, are more satisfactorily accounted for without their admission.

But it is unfortunately the nature of prejudices of opinion to adhere,

in a certain degree, to every mind, and to some with pertinacious

obstinacy, _pigris radicibus_, after all ground for their reasonable

entertainment is destroyed. Against such a disposition the student of

natural science must contend with all his power. Not that we are so

unreasonable as to demand of him an instant and peremptory dismission

of all his former opinions and judgments; all we require is, that

he will hold them without bigotry, retain till he shall see reason

to question them, and be ready to resign them when fairly proved

untenable, and to doubt them when the weight of probability is shown to

lie against them. If he refuse this, he is incapable of science.