(365.) Magnetism is remarkable in another important point of view. It

offers a prominent, or “_glaring instance_” of that quality in nature

which is termed _polarity_ (267.), and that under circumstances which

peculiarly adapt it for the study of this quality. It does not appear

that the ancients had any knowledge of this property of the magnet,

though its attraction of iron was well known to them. The first mention

of it in modern times cannot be traced earlier than 1180, though it

was probably known to the Chinese before that time. The polarity of

the magnet consists in this, that if suspended freely, one part of it

will invariably direct itself towards a certain point in the horizon,

the other towards the opposite point; and that, if two magnets, so

suspended, be brought near each other, there will take place a mutual

action, in consequence of which, the positions of both will be

disturbed, in the same manner as would happen if the corresponding

parts of each repelled, and those oppositely directed attracted, each

other; and by properly varying the experiment, it is found that they

really do so. If a small magnet, freely suspended, be brought into

the neighbourhood of a larger one, it will take a position depending

on the position of the _poles_ of the larger one, with respect to its

point of suspension. And it has been ascertained that these and all

other phenomena exhibited by magnets in their mutual attractions and

repulsions are explicable on the supposition of two forces or virtues

lodged in the particles of the magnets, the one predominating at one

end, the other at the other; and such that each particle shall attract

those in which the _opposite_ virtue to its own prevails, and repel

those in which a _similar_ one resides with a force proportional to the

inverse square of their mutual distance.

(366.) The direction in which a magnetic bar, or needle of steel,

freely suspended, places itself, has been ascertained to be different

at different points of the earth’s surface. In some places it points

exactly north and south, in others it deviates from this direction

more or less, and at some actually stands at right angles to it. This

remarkable phenomenon, which is called the variation of the needle,

and which was discovered by Sebastian Cabot in the year 1500, is

accompanied with another called the dip, noticed by Robert Norman in

1576. It consists in a tendency of a needle, nicely balanced on its

centre, when unmagnetized, to _dip_ or point downwards when rendered

magnetic, towards a point below the horizon, and situated within the

earth. By tracing the variation and dip over the whole surface of the

globe, it has been found that these phenomena take place as they would

do if the earth itself were a great magnet, having its poles deeply

situated below the surface,--and, what is very remarkable, possessing

a slow motion within it, in consequence of which neither the variation

nor dip remain constantly the same at the same place. The laws of this

motion are at present unknown; but the discovery of electro-magnetism,

by rendering it almost certain that the earth’s magnetism is merely an

effect of the continual circulation of great quantities of electricity

round it, in a direction generally corresponding with that of its

rotation, have dissipated the greater part of the mystery which hung

over these phenomena; since a variety of causes, both geological and

others, may be imagined which may produce considerable deviations in

the intensity, and partial ones in the direction, of such electric

currents. The unequal distribution of land and sea in the two

hemispheres, by affecting the operation of the sun’s heat in producing

evaporation from the latter, which is probably one of the great sources

of terrestrial electricity, may easily be conceived to modify the

general tendency of such currents, and to produce irregularities in

them, which may render a satisfactory account of whatever still appears

anomalous in the phenomena of terrestrial magnetism. This branch

of science thus becomes connected, on a great scale, with that of

meteorology, one of the most complicated and difficult, but at the same

time interesting, subjects of physical research; one, however, which

has of late begun to be studied with a diligence which promises the

speedy disclosure of relations and laws of which at present we can form

but a very imperfect notion.

(367.) The communication of magnetism from the earth to a magnetic

body, or from one magnetic body to another, is performed by a process

to which the name of induction has been given, and the laws and

properties of such induced magnetism have been studied with much

perseverance and success,--practically, by Gilbert, Boyle, Knight,

Whiston, Cavallo, Canton, Duhamel, Rittenhouse, Scoresby, and others;

and theoretically, by Æpinus, Coulomb, and Poisson, and in our own

country by Messrs. Barlow and Christie, who have investigated with

great care the curious phenomena which take place when masses of iron

are presented successively, in different positions, by rotation on

an axis, to the influence of the earth’s magnetism. The magnetism of

crystallized bodies (partly from the extreme rarity of such as are

susceptible of any considerable magnetic virtue) has not hitherto been

at all examined, but would probably afford very curious results.

(368.) To electricity the views of the physical enquirer now turn

from almost every quarter, as to one of those universal powers which

Nature seems to employ in her most important and secret operations.

This wonderful agent, which we see in intense activity in lightning,

and in a feebler and more diffused form traversing the upper regions

of the atmosphere in the northern lights, is present, probably in

immense abundance, in every form of matter which surrounds us, but

becomes sensible only when disturbed by excitements of peculiar

kinds. The most effectual of these is friction, which we have already

observed to be a powerful source of heat. Everybody is familiar

with the crackling sparks which fly from a cat’s back when stroked.

These, by proper management, may be accumulated in bodies suitably

disposed to receive them, and, although then no longer visible, give

evidence of their existence by the exhibition of a vast variety of

extraordinary phenomena,--producing attractions and repulsions in

bodies at a distance,--admitting of being transferred by contact, or

by sudden and violent transilience of the interval of separation, from

one body to another, under the form of sparks and flashes;--traversing

with perfect facility the substance of the densest metals, and a

variety of other bodies called conductors, but being detained by

others, such as glass, and especially _air_, which are thence called

non-conductors,--producing painful shocks and convulsive motions, and

even death itself if in sufficient quantity, in animals through which

they pass, and finally imitating, on a small scale, all the effects of

lightning.

(369.) The study of these phenomena and their laws until a

comparatively recent period occupied the entire attention of

electricians, and constituted the whole of the science of electricity.

It appears, as the result of their enquiries, that all the phenomena in

question are explicable on the supposition that electricity consists

in a rare, subtle, and highly elastic fluid, which in its tendency

to expand and diffuse itself pervades with more or less facility

the substance of conductors, but is obstructed and detained from

expansion more or less completely by non-conductors. It is supposed,

moreover, that this electric fluid possesses a power of attraction

for the particles of all ponderable matter, together with that of a

repulsion for particles of its own kind. Whether it has weight, or is

rather to be regarded as a species of matter distinct from that of

which ponderable bodies consist, is a question of such delicacy, that

no direct experiments have yet enabled us to decide it; but at all

events its _inertia_ compared with its elastic force must be conceived

excessively small, so that it is to be regarded as a fluid in the

highest degree _active_, obeying every impulse, internal or external,

with the greatest promptitude; in short, a fluid whose energies can

only be compared with those of the ethereal medium by which, in the

undulatory doctrine, light is supposed to be conveyed. The properties

of hydrogen gas compared with those of the denser aëriform fluids will,

in some slight degree, aid our conception of the excessive mobility and

penetrating activity of a fluid so constituted. Electricity, however,

must be regarded as differing in some remarkable points from all those

fluids to which we have hitherto been accustomed to apply the epithet

elastic, such as air, gases, and vapours. In these, the repulsive force

of the particles on which their elasticity depends is considered as

extending only to very small distances, so as to affect only those in

the immediate vicinity of each other, while their attractive power, by

which they obey the general gravitation of all matter, extends to any

distance. In electricity, on the other hand, the very reverse must be

admitted. The force by which its particles repel each other extends to

great distances, while its force of adhesion to ponderable matter must

be regarded as limited in its extent to such minute intervals as escape

observation.

(370.) The conception of a single fluid of this kind, which when

accumulated in excess in bodies tends constantly to escape, and seek

a restoration of equilibrium by communicating itself to any others

where there may be a deficiency, is that which occurs most naturally

to the mind, and was accordingly maintained by Franklin, to whom the

science of electricity is under great obligations for those decisive

experiments which informed us respecting the true nature of lightning.

The same theory was afterwards advocated by Æpinus, who first showed

how the laws of equilibrium of such a fluid might be reduced to strict

mathematical investigation. But there are phenomena accompanying its

transfer from body to body and the state of equilibrium it affects

under various circumstances, which appear to require the admission of

_two distinct fluids_ antagonist to each other, each attracting the

other, and repelling itself; but each, alike, susceptible of adhesion

to material substances, and of transfer more or less rapid from

particle to particle of them. These fluids in the natural undisturbed

state are conceived to exist in a state of combination and mutual

saturation; but this combination may be broken, and either of them

separately accumulated in a body to any amount without the other,

provided its escape be properly obstructed by surrounding it with

non-conductors. When so accumulated, its repulsion for its own kind

and attraction of the opposite species in neighbouring bodies tends

to disturb the natural equilibrium of the two fluids present in them,

and to produce phenomena of a peculiar description, which are termed

_induced_ electricity. Curious and artificial as this theory may

appear, there has hitherto been produced no phenomenon of which it

will not afford at least a plausible, and in by far the majority of

cases a very satisfactory, explanation. It has one character which is

extremely valuable in any theory, that of admitting the application of

strict mathematical reasoning to the conclusions we would draw from

it. Without this, indeed, it is scarcely possible that any theory

should ever be fairly brought to the test by a comparison with facts.

Accordingly, the mathematical theory of electrical equilibrium,

and the laws of the distribution of the electric fluids over the

surfaces of bodies in which they are accumulated, have been made the

subject of elaborate geometrical investigation by the most expert

mathematicians, and have attained a degree of extent and elegance

which places this branch of science in a very high rank in the scale

of mathematico-physical enquiry. These researches are grounded on

the assumption of a law of attraction and repulsion similar to those

of gravity and magnetism, and which by the general accordance of the

results with facts, as well as by experiments instituted for the

express purpose of ascertaining the laws in question, are regarded as

sufficiently demonstrated.

(371.) The most obscure part of the subject is no doubt the original

mode of disturbance of electrical equilibrium, by which electricity is

excited in the first instance, either by friction or by any other of

those causes which have been ascertained to produce such an effect:

analogies, it is true, are not wanting[56]; but it must be allowed that

hitherto nothing decisive has been offered on the subject; and that

conjectural modes of action have in this instance too often usurped the

place of those to which a careful examination of facts alone can lead

us.

(372.) Philosophers had long been familiar with the effects of

electricity above referred to, and with those which it produces in

its sudden and violent transfer from one body to another, in rending

and shattering the parts of the substances through which it passes,

and where in great quantity, producing all the effect of intense

heat, igniting, fusing, and volatilizing metals, and setting fire to

inflammable bodies; even its occasional influence in destroying or

altering the polarity of the magnetic needle had been noticed: but as

heat was known to be produced by mechanical violence, and as magnetism

was also known to be greatly affected by the same cause, these effects

were referred rather to that cause than to any thing in the peculiar

nature of the electric matter, and regarded rather as an indirect

consequence of its mode of action than as connected with its intimate

nature. In short, electricity seemed destined to furnish another in

addition to many instances of subjects insulated from the rest of

philosophy, and capable of being studied only in its own internal

relations, when the great discoveries of Galvani and Volta placed a new

power at the command of the experimenter, by whose means those effects

which had before been crowded within an inappreciable instant could

be developed in detail and studied at leisure; and those forces which

had previously exhibited themselves only in a state of uncontrollable

intensity were tamed down, as it were, and made to distribute their

efficacy over an indefinite time, and to regulate their action at the

will of the operator. It was then soon ascertained that electricity

in the act of its passage along conductors, produces a variety of

wonderful effects, which had never been previously suspected; and these

of such a nature, as to afford points of contact with several other

branches of physical enquiry, and to throw new and unexpected lights on

some of the most obscure operations of nature.

(373.) The history of this grand discovery affords a fine illustration

of the advantage to be derived in physical enquiry from a close and

careful attention to any phenomenon, however apparently trifling,

which may at the moment of observation appear inexplicable on received

principles. The convulsive motions of a dead frog in the neighbourhood

of an electric discharge, which originally drew Galvani’s attention to

the subject, had been noticed by others nearly a century before his

time, but attracted no further remark than as indicating a peculiar

sensibility to electrical excitement depending on that remnant of

vitality which is not extinguished in the organic frame of an animal

by the deprivation of actual life. Galvani was not so satisfied. He

analysed the phenomenon; and in investigating all the circumstances

connected with it was led to the observation of a peculiar electrical

excitement which took place when a circuit was formed of three distinct

parts, a muscle, a nerve, and a metallic conductor, each placed in

contact with the other two, and which was manifested by a convulsive

motion produced in the muscle. To this phenomenon he gave the name of

animal electricity, an unfortunate epithet, since it tended to restrict

enquiry into its nature to the class of phenomena in which it first

became apparent. But this circumstance, which in a less enquiring age

of science might have exercised a fatal influence on the progress of

knowledge, proved happily no obstacle to the further developement of

its principles, the subject being immediately taken up with a kind

of prophetic ardour by Volta, who at once generalized the phenomena,

rejecting the physiological considerations introduced by Galvani, as

foreign to the enquiry, and regarding the contraction of the muscles

as merely a delicate means of detecting the production of electrical

excitements too feeble to be rendered sensible by any other means.

It was thus that he arrived at the knowledge of a general fact, that

of the disturbance of electrical equilibrium by the mere contact of

different bodies, and the circulation of a current of electricity in

one constant direction, through a circuit composed of three different

conductors. To increase the intensity of the very minute and delicate

effect thus observed became his next aim, nor did his enquiry terminate

till it had placed him in possession of that most wonderful of all

human inventions, the pile which bears his name, through the medium of

a series of well conducted and logically combined experiments, which

has rarely, if ever, been surpassed in the annals of physical research.

(374.) Though the original pile of Volta was feeble compared to those

gigantic combinations which were afterwards produced, it sufficed,

however, to exhibit electricity under a very different aspect from any

thing which had gone before, and to bring into view those peculiar

modifications in its action which Dr. Wollaston was the first to

render a satisfactory account of, by referring them to an increase

of _quantity_, accompanied with a diminution of _intensity_ in the

supply afforded. The discovery had not long been made public, and

the instrument in the hands of chemists and electricians, before it

was ascertained that the electric current, transmitted by it through

conducting liquids, produces in them chemical decompositions. This

capital discovery appears to have been made, in the first instance, by

Messrs. Nicholson and Carlisle, who observed the decomposition of water

so produced. It was speedily followed up by the still more important

one of Berzelius and Hisinger, who ascertained it as a general law,

that, in all the decompositions so effected, the acids and oxygen

become transferred to, and accumulated around, the positive,--and

hydrogen, metals, and alkalies round the negative, pole of a Voltaic

circuit; being transferred in an invisible, and, as it were, a latent

or torpid state, by the action of the electric current, through

considerable spaces, and even through large quantities of water or

other liquids, again to re-appear with all their properties at their

appropriate resting-places.

(375.) It was in this state of things that the subject was taken up

by Davy, who, seeing that the strongest chemical affinities were thus

readily subverted by the decomposing action of the pile, conceived

the happy idea of bringing to bear the intense power of the enormous

batteries of the Royal Institution on those substances which, though

strongly suspected to be compounds, had resisted all attempts to

decompose them--the alkalies and earths. They yielded to the force

applied, and a total revolution was thus effected in chemistry; not so

much by the introduction of the new elements thus brought to light, as

by the mode of conceiving the nature of chemical affinity, which from

that time has been regarded (as Davy broadly laid it down, in a theory

which was readily adopted by the most eminent chemists, and by none

more readily than by Berzelius himself,) as entirely due to electric

attractions and repulsions, those bodies combining most intimately

whose particles are habitually in a state of the most powerful

electrical antagonism, and dispossessing each other, according to the

amount of their difference in this respect.

(376.) The connection of magnetism and electricity had long been

suspected, and innumerable fruitless trials had been made to determine,

in the affirmative or negative, the question of such connection. The

phenomena of many crystallized minerals which become electric by heat,

and develope opposite electric poles at their two extremities, offered

an analogy so striking to the polarity of the magnet, that it seemed

hardly possible to doubt a closer connection of the two powers. The

developement of a similar polarity in the Voltaic pile pointed strongly

to the same conclusion; and experiments had even been made with a

view to ascertain whether a pile in a state of excitement might not

manifest a disposition to place itself in the magnetic meridian; but

the essential condition had been omitted, that of allowing the pile to

discharge itself freely, a condition which assuredly never would have

occurred of itself to any experimenter. Of all the philosophers who

had speculated on this subject, none had so pertinaciously adhered to

the idea of a necessary connection between the phenomena as Oërsted.

Baffled often, he returned to the attack; and his perseverance was at

length rewarded by the complete disclosure of the wonderful phenomena

of electro-magnetism. There is something in this which reminds us of

the obstinate adherence of Columbus to his notion of the necessary

existence of the New World; and the whole history of this beautiful

discovery may serve to teach us reliance on those general analogies

and parallels between great branches of science by which one strongly

reminds us of another, though no direct connection appears; as an

indication not to be neglected of a community of origin.

(377.) It is highly probable that we are still ignorant of many

interesting features in electrical science, which the study of the

Voltaic circuit will one day disclose. The violent mechanical effects

produced by it on mercury, placed under conducting liquids which have

been referred by Professor Erman to a modified form of capillary

attraction, but which a careful and extended view of the phenomena

have led others[57] to regard in a very different light, as pointing

out a primary action of a dynamical rather than a statical character,

deserve, in this point of view, a further investigation; and the

curious relations of electricity to heat, as exhibited in the phenomena

of what has been called thermo-electricity, promise an ample supply of

new information.

(378.) Among the remarkable effects of electricity disclosed by the

researches of Galvani and Volta, perhaps the most so consisted in its

influence on the nervous system of animals. The origin of muscular

motion is one of those profound mysteries of nature which we can

scarcely venture to hope will ever be fully explained. Physiologists,

however, had long entertained a general conception of the conveyance

of some subtle fluid or spirit from the brain to the muscles of

animals along the nerves; and the discovery of the rapid transmission

of electricity along conductors, with the violent effects produced by

shocks, transmitted through the body, on the nervous system, would

very naturally lead to the idea that this nervous fluid, if it had

any real existence, might be no other than the electrical. But until

the discoveries of Galvani and Volta, this could only be looked upon

as a vague conjecture. The character of a _vera causa_ was wanting to

give it any degree of rational plausibility, since no reason could

be imagined for the disturbance of the electrical equilibrium in the

animal frame, composed as it is entirely of conductors, or rather, it

seemed contrary to the then known laws of electrical communication

to suppose any such. Yet one strange and surprising phenomenon might

be adduced indicative of the possibility of such disturbance, viz.

the powerful shock given by the torpedo and other fishes of the same

kind, which presented so many analogies with those arising from

electricity, that they could hardly be referred to a different source,

though _besides_ the shock neither spark nor any other indication of

electrical tension could be detected in them.

(379.) The benumbing effect of the torpedo had been ascertained to

depend on certain singularly constructed organs composed of membranous

columns, filled from end to end with laminæ, separated from each other

by a fluid: but of its mode of action no satisfactory account could be

given; nor was there any thing in its construction, and still less in

the nature of its materials, to give the least ground for supposing

it an electrical apparatus. But the pile of Volta supplied at once

the analogies both of structure and of effect, so as to leave little

doubt of the electrical nature of the apparatus, or of the power, a

most wonderful one certainly, of the animal, to determine, by an effort

of its will, that concurrence of conditions on which its activity

depends. This remained, as it probably ever will remain, mysterious

and inexplicable; but the principle once established, that there

exists in the animal economy a power of determining the developement

of electric excitement, capable of being transmitted along the nerves,

and it being ascertained, by numerous and decisive experiments, that

the transmission of Voltaic electricity along the nerves of even

a dead animal is sufficient to produce the most violent muscular

action, it became an easy step to refer the origin of muscular motion

in the living frame to a similar cause; and to look to the brain, a

wonderfully constituted organ, for which no mode of action possessing

the least plausibility had ever been devised, as the source of the

required electrical power.[58]

(380.) It is not our intention, however, to enter into any further

consideration of physiological subjects. They form, it is true, a

most important and deeply interesting province of philosophical

enquiry; but the view that we have taken of physical science has

rather been directed to the study of inanimate nature, than to that of

the mysterious phenomena of organization and life, which constitute

the object of physiology. The history of the animal and vegetable

productions of the globe, as affording objects and materials for the

convenience and use of man, and as dependent on and indicative of the

general laws which determine the distribution of heat, moisture, and

other natural agents, over its surface, and the revolutions it has

undergone, are of course intimately connected with our subject, and

will, therefore, naturally afford room for some remarks, but not such

as will long detain the reader’s attention.

(381.) In _zoology_, the connection of peculiar modes of life and

food, with peculiarities of structure, has given rise to systems of

classification at once obvious and natural; and the great progress

which has been made in comparative anatomy has enabled us to trace

a graduated scale of organization almost through the whole chain of

animal being; a scale not without its intervals, but which every

successive discovery of animals heretofore unknown has tended to fill

up. The wonders disclosed by microscopic observation have opened to

us a new world, in which we discover, with astonishment, the extremes

of minuteness and complexity of structure united; while, on the other

hand, the examination of the fossil remains of a former state of

creation has demonstrated the existence of animals far surpassing in

magnitude those now living, and brought to light many forms of being

which have nothing analogous to them at present, and many others

which afford important connecting links between existing genera. And,

on the other hand, the researches of the comparative anatomist and

conchologist have thrown the greatest light on the studies of the

geologist, and enabled him to discern, through the obscure medium of a

few relics, scattered here and there through a stratum, circumstances

connected with the formation of the stratum itself which he could have

recognised by no other indication. This is one among many striking

instances of the unexpected lights which sciences, however apparently

remote, may throw upon each other.

(382.) To _botany_ many of the same remarks apply. Its artificial

systems of classification, however convenient, have not prevented

botanists from endeavouring to group together the objects of their

science in natural classes having a community of character more

intimate than those which determine their place in the Linnean or any

similar system; a community of character extending over the whole

habit and properties of the individuals compared. The important

chemical discoveries which have been lately made of peculiar proximate

principles which, in an especial manner, characterize certain

families of plants, hold out the prospect of a greatly increased

field of interesting knowledge in this direction, and not only

interesting, but in a high degree important, when it is considered

that the principles thus brought into view are, for the most part,

very powerful medicines, and are, in fact, the essential ingredients

on which the medical virtues of the plants depend. The law of the

distribution of the generic forms of plants over the globe, too, has,

within a comparatively recent period, become an object of study to the

naturalist; and its connection with the laws of climate constitutes one

of the most interesting and important branches of natural-historical

enquiry, and one on which great light remains to be thrown by future

researches. It is this which constitutes the chief connecting link

between botany and geology, and renders a knowledge of the vegetable

fossils, of any portion of the earth’s surface, indispensable to the

formation of a correct judgment of the circumstances under which it

existed in its ancient state. Fossil botany is accordingly cultivated

with great and increasing ardour; and the subterraneous “Flora” of a

geological formation is, in many instances, studied with a degree of

care and precision little inferior to that which its surface exhibits.

CHAP. VI.

OF THE CAUSES OF THE ACTUAL RAPID ADVANCE OF THE PHYSICAL SCIENCES

COMPARED WITH THEIR PROGRESS AT AN EARLIER PERIOD.

(383.) There is no more extraordinary contrast than that presented by

the slow progress of the physical sciences, from the earliest ages

of the world to the close of the sixteenth century, and the rapid

developement they have since experienced. In the former period of

their history, we find only small additions to the stock of knowledge,

made at long intervals of time; during which a total indifference

on the part of the mass of mankind to the study of nature operated

to effect an almost complete oblivion of former discoveries, or,

at best, permitted them to linger on record, rather as literary

curiosities, than as possessing, in themselves, any intrinsic interest

and importance. A few enquiring individuals, from age to age, might

perceive their value, and might feel that irrepressible thirst after

knowledge which, in minds of the highest order, supplies the absence

both of external stimulus and opportunity. But the total want of a

right direction given to enquiry, and of a clear perception of the

objects to be aimed at, and the advantages to be gained by systematic

and connected research, together with the general apathy of society

to speculations remote from the ordinary affairs of life, and

studiously kept involved in learned mystery, effectually prevented

these occasional impulses from overcoming the inertia of ignorance, and

impressing any regular and steady progress on science. Its objects,

indeed, were confined in a region too sublime for vulgar comprehension.

An earthquake, a comet, or a fiery meteor, would now and then call the

attention of the whole world, and produce from all quarters a plentiful

supply of crude and fanciful conjectures on their causes; but it was

never supposed that sciences could exist among common objects, have a

place among mechanical arts, or find worthy matter of speculation in

the mine or the laboratory. Yet it cannot be supposed, that all the

indications of nature continually passed unremarked, or that much good

observation and shrewd reasoning on it failed to perish unrecorded,

before the invention of printing enabled every one to make his ideas

known to all the world. The moment this took place, however, the sparks

of information from time to time struck out, instead of glimmering

for a moment, and dying away in oblivion, began to accumulate into a

genial glow, and the flame was at length kindled which was speedily to

acquire the strength and rapid spread of a conflagration. The universal

excitement in the minds of men throughout Europe, which the first

out-break of modern science produced, has been already spoken of. But

even the most sanguine anticipators could scarcely have looked forward

to that steady, unintermitted progress which it has since maintained,

nor to that rapid succession of great discoveries which has kept up

the interest of the first impulse still vigorous and undiminished. It

may truly, indeed, be said, that there is scarcely a single branch of

physical enquiry which is either stationary, or which has not been,

for many years past, in a constant state of advance, and in which the

progress is not, at this moment, going on with accelerated rapidity.

(384.) Among the causes of this happy and desirable state of things,

no doubt we are to look, in the first instance, to that great

increase in wealth and civilization which has at once afforded the

necessary leisure and diffused the taste for intellectual pursuits

among numbers of mankind, which have long been and still continue

steadily progressive in every principal European state, and which the

increase and fresh establishment of civilized communities in every

distant region are rapidly spreading over the whole globe. It is not,

however, merely the increased number of cultivators of science, but

their enlarged opportunities, that we have here to consider, which, in

all those numerous departments of natural research that require local

information, is in fact the most important consideration of all. To

this cause we must trace the great extension which has of late years

been conferred on every branch of natural history, and the immense

contributions which have been made, and are daily making, to the

departments of zoology and botany, in all their ramifications. It is

obvious, too, that all the information that can possibly be procured,

and reported, by the most enlightened and active travellers, must fall

infinitely short of what is to be obtained by individuals actually

resident upon the spot. Travellers, indeed, may make collections,

may snatch a few hasty observations, may note, for instance, the

distribution of geological formations in a few detached points, and now

and then witness remarkable local phenomena; but the resident alone can

make continued series of regular observations, such as the scientific

determination of climates, tides, magnetic variations, and innumerable

other objects of that kind, requires; can alone mark all the details

of geological structure, and refer each stratum, by a careful and long

continued observation of its fossil contents, to its true epoch; can

alone note the habits of the animals of his country, and the limits

of its vegetation, or obtain a satisfactory knowledge of its mineral

contents, with a thousand other particulars essential to that complete

acquaintance with our globe as a whole, which is beginning to be

understood by the extensive designation of physical geography. Besides

which, ought not to be omitted multiplied opportunities of observing

and recording those extraordinary phenomena of nature which offer an

intense interest, from the rarity of their occurrence as well as the

instruction they are calculated to afford. To what, then, may we not

look forward, when a spirit of scientific enquiry shall have spread

through those vast regions in which the process of civilization, its

sure precursor, is actually commenced and in active progress? And what

may we not expect from the exertions of powerful minds called into

action under circumstances totally different from any which have yet

existed in the world, and over an extent of territory far surpassing

that which has hitherto produced the whole harvest of human intellect?

In proportion as the number of those who are engaged on each department

of physical enquiry increases, and the geographical extent over which

they are spread is enlarged, a proportionately increased facility

of communication and interchange of knowledge becomes essential to

the prosecution of their researches with full advantage. Not only

is this desirable, to prevent a number of individuals from making

the same discoveries at the same moment, which (besides the waste of

valuable time) has always been a fertile source of jealousies and

misunderstandings, by which great evils have been entailed on science;

but because methods of observation are continually undergoing new

improvements, or acquiring new facilities, a knowledge of which, it is

for the general interest of science, should be diffused as widely and

as rapidly as possible. By this means, too, a sense of common interest,

of mutual assistance, and a feeling of sympathy in a common pursuit,

are generated, which proves a powerful stimulus to exertion; and, on

the other hand, means are thereby afforded of detecting and pointing

out mistakes before it is too late for their rectification.

(385.) Perhaps it may be truly remarked, that, next to the

establishment of institutions having either the promotion of science

in general, or, what is still more practically efficacious in its

present advanced state, that of particular departments of physical

enquiry, for their express objects, nothing has exercised so powerful

an influence on the progress of modern science as the publication

of monthly and quarterly scientific journals, of which there is now

scarcely a nation in Europe which does not produce several. The quick

and universal circulation of these, places observers of all countries

on the same level of perfect intimacy with each other’s objects and

methods, while the abstracts they from time to time (if well conducted)

contain of the most important researches of the day consigned to the

more ponderous tomes of academical collections, serve to direct the

course of general observation, as well as to hold out, in the most

conspicuous manner, models for emulative imitation. In looking forward

to what may hereafter be expected from this cause of improvement, we

are not to forget the powerful effect which must in future be produced

by the spread of elementary works and digests of what is actually known

in each particular branch of science. Nothing can be more discouraging

to one engaged in active research, than the impression that all he

is doing may, very likely, be labour taken in vain; that it may,

perhaps, have been already done, and much better done, than, with his

opportunities, or his resources, he can hope to perform it; and, on the

other hand, nothing can be more exciting than the contrary impression.

Thus, by giving a connected view of what has been done, and what

remains to be accomplished in every branch, those digests and bodies

of science, which from time to time appear, have, in fact, a very

important weight in determining its future progress, quite independent

of the quantity of information they communicate. With respect to

elementary treatises, it is needless to point out their utility, or

to dwell on the influence which their actual abundance, contrasted

with their past remarkable deficiency, is likely to exercise over the

future. It is only by condensing, simplifying, and arranging, in the

most lucid possible manner, the acquired knowledge of past generations,

that those to come can be enabled to avail themselves to the full of

the advanced point from which they will start.

(386.) One of the means by which an advanced state of physical science

contributes greatly to accelerate and secure its further progress,

is the exact knowledge acquired of physical data, or those normal

quantities which we have more than once spoken of in the preceding

pages (222.); a knowledge which enables us not only to appretiate

the accuracy of experiments, but even to correct their results. As

there is no surer criterion of the state of science in any age than

the degree of care bestowed, and discernment exhibited, in the choice

of such data, so as to afford the simplest possible grounds for the

application of theories, and the degree of accuracy attained in their

determination, so there is scarcely any thing by which science can be

more truly benefited than by researches directed expressly to this

object, and to the construction of tables exhibiting the true numerical

relations of the elements of theories, and the actual state of nature,

in all its different branches. It is only by such determinations that

we can ascertain what changes are slowly and imperceptibly taking place

in the existing order of things; and the more accurate they are, the

_sooner_ will this knowledge be acquired. What might we not now have

known of the motions of the (so-called) fixed stars, had the ancients

possessed the means of observation we now possess, and employed them

as we employ them now?

(387.) In any enumeration of causes which have contributed to

the recent rapid advancement of science, we must not forget the

very important one of improved and constantly improving means of

observation, both in instruments adapted for the exact measurement of

quantity, and in the general convenience and well-judged adaptation

to its purposes, of every description of scientific apparatus. In

the actual state of science there are few observations which can

be productive of any great advantage but such as afford accurate

measurement; and an increased refinement in this respect is constantly

called for. The degree of delicacy actually attained, we will not say

in the most elaborate works of the highest art, but in such ordinary

apparatus as every observer may now command, is such as could not have

been arrived at unless in a state of the mechanical arts, which in

its turn (such is the mutual re-action of cause and effect) requires

for its existence a very advanced state of science. What an important

influence may be exercised over the progress of a single branch of

science by the invention of a ready and convenient mode of executing a

definite measurement, and the construction and common introduction of

an instrument adapted for it cannot be better exemplified than by the

instance of the reflecting goniometer. This simple, cheap, and portable

little instrument, has changed the face of mineralogy, and given it all

the characters of one of the exact sciences.

(388.) Our means of perceiving and measuring minute quantities, in the

important relations of weight, space, and time, seem already to have

been carried to a point which it is hardly conceivable they should

surpass. Balances have been constructed which have rendered sensible

the millionth part of the whole quantity weighed; and to turn with the

thousandth part of a grain is the performance of balances pretending

to no very extraordinary degree of merit. The elegant invention of

the sphærometer, by substituting the sense of touch for that of sight

in the measurement of minute objects, permits the determination of

their dimensions with a degree of precision which is fully adequate

to the nicest purposes of scientific enquiry. By its aid an inch may

be readily subdivided into ten or even twenty thousand parts; and the

lever of contact, an instrument in use among the German opticians,

enables us to appretiate quantities of space even yet smaller. For

the subdivision of time, too, the perfection of modern mechanism has

furnished resources which leave very little to be desired. By the

aid of clocks and chronometers, as they are now constructed, a few

tenths of a second is all the error that need be apprehended in the

subdivision of a day; and for the further subdivision of smaller

portions of time, instruments have been imagined which admit of

almost unlimited precision, and permit us to appreciate intervals to

the nicety of the hundredth, or even the thousandth part of a single

second.[59] When the precision attainable by such means is contrasted

with what could be procured a few generations ago, by the rude and

clumsy workmanship of even the early part of the last century, it will

be no matter of astonishment that the sciences which depend on exact

measurements should have made a proportional progress. Nor will any

degree of nicety in physical determinations appear beyond our reach, if

we consider the inexhaustible resources which science itself furnishes,

in rendering the quantities actually to be determined by measure great

multiples of the elements required for the purposes of theory, so as to

diminish in the same proportion the influence of any errors which may

be committed on the final results.

(389.) Great, indeed, as have been of late the improvements in the

construction of instruments, both as to what regards convenience and

accuracy, it is to the discovery of improved _methods_ of observation

that the chief progress of those parts of science which depend on

exact determinations is owing. The balance of torsion, the ingenious

invention of Cavendish and Coulomb, may be cited as an example of what

we mean. By its aid we are enabled not merely to render sensible,

but to subject to precise measurement and subdivision, degrees of

force infinitely too feeble to affect the nicest balance of the usual

construction, even were it possible to bring them to act on it. The

galvanometer, too, affords another example of the same kind, in an

instrument whose range of utility lies among electric forces which we

have no other means of rendering sensible, much less of estimating

with exactness. In determinations of quantities less minute in

themselves, the methods devised by Messrs. Arago and Fresnel, for the

measurement of the refractive powers of transparent media by means of

the phenomenon of diffraction, may be cited as affording a degree of

precision limited only by the wishes of the observer, and the time and

patience he is willing to devote to his observation. And in respect of

the direction of observations to points from which real information

is to be obtained, and positive conclusions drawn, the hygrometer of

Daniell may be cited as an elegant example of the introduction into

general use of an instrument substituting an indication founded on

strict principles for one perfectly arbitrary.

(390.) In speculating on the future prospects of physical science,

we should not be justified in leaving out of consideration the

probability, or rather certainty, of the occasional occurrence of those

happy accidents which have had so powerful an influence on the past;

occasions, where a fortunate combination opportunely noticed may admit

us in an instant to the knowledge of principles of which no suspicion

might occur but for some such casual notice. Boyle has entitled one of

his essays thus remarkably,--“_Of Man’s great Ignorance of the Uses

of natural Things; or that there is no one Thing in Nature whereof

the Uses to human Life are yet thoroughly understood_.”[60] The whole

history of the arts since Boyle’s time has been one continued comment

on this text; and if we regard among the uses of the works of nature,

_that_, assuredly the noblest of all, which leads us to a knowledge

of the Author of nature through the contemplation of the wonderful

means by which he has wrought out his purposes in his works, the

sciences have not been behind hand in affording their testimony to its

truth. Nor are we to suppose that the field is in the slightest degree

narrowed, or the chances in favour of such fortunate discoveries at all

decreased, by those which have already taken place: on the contrary,

they have been incalculably extended. It is true that the ordinary

phenomena which pass before our eyes have been minutely examined, and

those more striking and obvious principles which occur to superficial

observation have been noticed and embodied in our systems of science;

but, not to mention that by far the greater part of natural phenomena

remain yet unexplained, every new discovery in science brings into

view whole classes of facts which would never otherwise have fallen

under our notice at all, and establishes relations which afford to

the philosophic mind a constantly extending field of speculation,

in ranging over which it is next to impossible that he should not

encounter new and unexpected principles. How infinitely greater, for

instance, are the mere chances of discovery in chemistry among the

innumerable combinations with which the modern chemist is familiar,

than at a period when two or three imaginary elements, and some ten

or twenty substances, whose properties were known with an approach to

distinctness, formed the narrow circle within which his ideas had to

revolve? How many are the instances where a new substance, or a new

property, introduced into familiar use, by being thus brought into

relation with all our actual elements of knowledge, has become the

means of developing properties and principles among the most common

objects, which could never have otherwise been discovered? Had not

platina (to take an instance) been an object of the most ordinary

occurrence in a laboratory, would a suspicion have ever occurred that

a lamp could be constructed to burn without flame; and should we have

ever arrived at a knowledge of those curious phenomena and products of

semi-combustion which this beautiful experiment discloses?

(391.) Finally, when we look back on what has been accomplished in

science, and compare it with what remains to be done, it is hardly

possible to avoid being strongly impressed with the idea that we have

been and are still executing the labour by which succeeding generations

are to profit.[61] In a few instances only have we arrived at those

general axiomatic laws which admit of direct deductive inference,

and place the solutions of physical phenomena before us as so many

problems, whose principles of solution we fully possess, and which

require nothing but acuteness of reasoning to pursue even into their

farthest recesses. In fewer still have we reached that command of

abstract reasoning itself which is necessary for the accomplishment of

so arduous a task. Science, therefore, in relation to our faculties,

still remains boundless and unexplored, and, after the lapse of a

century and a half from the æra of Newton’s discoveries, during which

every department of it has been cultivated with a zeal and energy which

have assuredly met their full return, we remain in the situation in

which he figured himself,--standing on the shore of a wide ocean, from

whose beach we may have culled some of those innumerable beautiful

productions it casts up with lavish prodigality, but whose acquisition

can be regarded as no diminution of the treasures that remain.

(392.) But this consideration, so far from repressing our efforts, or

rendering us hopeless of attaining any thing intrinsically great, ought

rather to excite us to fresh enterprise, by the prospect of assured

and ample recompense from that inexhaustible store which only awaits

our continued endeavours. “It is no detraction from human capacity to

suppose it incapable of infinite exertion, or of exhausting an infinite

subject.”[62] In whatever state of knowledge we may conceive man to

be placed, his progress towards a yet higher state need never fear a

check, but must continue till the last existence of society.

(393.) It is in this respect an advantageous view of science, which

refers all its advances to the discovery of general laws, and to

the inclusion of what is already known in generalizations of still

higher orders; inasmuch as this view of the subject represents it, as

it really is, essentially incomplete, and incapable of being fully

embodied in any system, or embraced by any single mind. Yet it must be

recollected that, so far as our experience has hitherto gone, every

advance towards generality has at the same time been a step towards

simplification. It is only when we are wandering and lost in the mazes

of particulars, or entangled in fruitless attempts to work our way

downwards in the thorny paths of applications, to which our reasoning

powers are incompetent, that nature appears complicated:--the moment we

contemplate it as it is, and attain a position from which we can take a

commanding view, though but of a small part of its plan, we never fail

to recognise that sublime simplicity on which the mind rests satisfied

that it has attained the truth.

INDEX.

Acoustics cultivated by Pythagoras and Aristotle, page 248.

Æpinus, his laws of equilibrium of electricity, 332.

Aëriform fluids, liquids kept in a state of vapour, 321.

Agricola, George, his knowledge of mineralogy and metallurgy, 112.

Air, compressibility and elasticity of; limitation to the repulsive

tendency of, 226.

Weight of, unknown to the ancients, 228.

First perceived by Galileo, 228.

Proved by a crucial instance, 229.

Equilibrium of, established, 231.

Dilatation of, by heat, 319.

Air-pump, discovery of, 230.

Airy, his experiments in Dolcoath mine, 187.

Alchemists, advantages derived from, 11.

Algebra, 19.

Ampere, his electro-dynamic theory, 202.

Utility of, 203, 324.

Analysis of force, 86.

Of motion, 87.

Of complex phenomena, 88.

Anaxagoras, philosophy of, 107.

Animal electricity, 337.

Arago, M., his experiment with a magnetic needle and a plate of

copper, 157.

Archimedes, his practical application of science, 72.

His knowledge of hydrostatics, 231.

Arfwedson, his discovery of lithia, 158.

Aristotle, his knowledge of natural history, 109.

His works condemned, and subsequently studied with avidity, 111.

His philosophy overturned by the discoveries of Copernicus, Kepler,

and Galileo, 113.

Arithmetic, 19.

Art, empirical and scientific, differences between, 71.

Remarks on the language, terms, or signs, used in treating of

it, 70.

Assurances, life, utility and abuses of, 58.

Astronomy, cause of the slow progress of our knowledge of, 78.

Theory and practical observations distinct in, 132.

An extensive acquaintance with science and every branch of knowledge

necessary to make a perfect observer in, 132.

Five primary planets added to our system, 274.

Positions, figures, and dimensions of all the planetary orbits now

well known, 275.

Atomic theory, 305.

Advantage of, 306.

Atomic weights of chemical elements, 306.

Attraction, capillary, or capillarity, investigated by Laplace and

Young, 234.

Bacon, celebrated in England for his knowledge of science, 72.

Benefits conferred on Natural Philosophy by him, 104.

His Novum Organum, 105.

His reform in philosophy proves the paramount importance of

induction, 114.

His prerogative of facts, 181.

Illustrated by the fracture of a crystallized substance, 183.

His collective instances, 184.

Importance of, 185.

His experiment on the weight of bodies, 186.

Travelling instances of, frontier instances of, 188.

His difference between liquids and aëriform fluids, 233.

Bartolin, Erasmus, first discovers the phenomena exhibited by doubly

refracting crystals, 254.

Beccher, phlogistic doctrines of, 300.

Bergmann, his advancement in crystallography, 239.

Bernoulli, experiments of, in hydrodynamical science, 181.

Biot, his hypothesis of a rotatory motion of the particles of light

about their axes, 262.

Black, Dr., his discovery of latent heat, 322.

Bode, his curious law observed in the progression of the magnitudes of

the several planetary orbits, 308.

Bodies, natural constitution of, 221.

Division of, into crystallized and uncrystallized, 242.

Bones, dry, a magazine of nutriment, 65.

Borda, his invention for subdivision, 128.

Botany, general utility of, 345.

Boyle, Robert, his enthusiasm in the pursuit of science, 115.

His improvement on the air-pump, 230.

Brain, hypothesis of its being an electric pile, 343.

Bramah’s press, principle and utility of, 233.

Brewster, Dr., his improvement on lenses for lighthouses, 56.

His researches prove that the phenomena exhibited by polarized

light, in its transmission through crystals, afford a certain

indication of the most important points relating to the

structure of crystals themselves, 263.

Cabot, Sebastian, his discovery of the variation of the needle, 327.

Cagnard, Baron de la Tour, utility of his experiments, 234.

Causes and consequences directors of the will of man, 6.

Causes, proximate, discovery of, called by Newton _veræ causæ_, 144.

Celestial mechanics, 265.

Chaldean records, 265.

Chemistry furnishes causes of sudden action, also fulminating

compositions, 62.

Analogy of the complex phenomena of, with those of physics, 92.

Benefits arising from the analysis of, 94.

Axioms of, analogous to those of geometry, 95.

Many of the new elements of, detected in the investigation of

residual phenomena, 158.

The most general law of, 209.

Illustration of, 210.

Between fifty and sixty elements in, 211.

Objects of, 296.

General heads of the principal improvements in, 302.

Remarks on those general heads, 304.

Chemistry, Stahlian, cause of the mistakes and confusions of, 123.

Chladni, experiments of, in dynamical science, 181.

Chlorine, disinfectant powers of, 56.

Clarke, Dr., his experiments on the arseniate and phosphate

of soda, 170.

His success in producing a new phosphate of soda, 171.

Climate, change of, in large tracts of the globe, alleged

cause of, 145.

Coals, power of a bushel of, properly consumed, 59.

Quantity consumed in London, 60.

Cohesion, an ultimate phenomenon, 90.

Cold, qualities of, 318.

Compass, mariner’s, 55.

Condensation, a source of heat, 313.

Conduction of heat, laws of, 205.

Copernicus, effect of his discoveries on the Aristotelian

philosophy, 113.

Objections to his astronomical doctrines, 269.

Crystallography, laws of, 123, 239.

A determinate figure supposed to be common to all the particles of a

crystal, 242.

D’Alembert, his improvements in hydrodynamics, 236.

Dalton, his announcement of the atomic theory, 305.

His examination of gases and vapours, 319.

Davy, Sir H., brings the voltaic pile to bear upon the earths and

alkalies, 339.

Deduction, utility of, 174.

De l’Isle, Romé, his study of crystalline bodies, 239.

Dew, causes of, investigated, 159.

Effects of, on different substances, 160.

Objects capable of contracting it, 161.

A cloudless sky favourable to its production, 162.

General proximate cause of, 163.

Drummond, lieutenant, his improvement on lenses for lamps of

lighthouses, 56.

Dynamics, importance of, 96, 223.

Earth, the orbit of,--diminution of its eccentricity round

the sun, 147.

Economy, political, 73.

Egypt, great pyramid of, height, weight, and ground occupied by

it, 60.

Accuracy of the astronomical records of, 265.

Elasticity, an ultimate phenomenon, 90.

Electricity may be the cause of magnetism, 93.

Universality of, 329.

Effects of, 330.

Activity of, 331.

Equilibrium of, 332.

Productive of chemical decomposition, 338.

Empirical laws, 178.

Evils resulting from, 179.

Encke, professor, his prediction of the return of the comet so many

times in succession, 156.

Englefield, sir H., his analysis of a solar beam, 314.

Equilibrium maintained by force, 222.

Erman, professor, his opinion of the effects of the voltaic

circuit, 340.

Euler, his improvement on Newton’s theory of sound, 247.

Experience, source of our knowledge of nature’s laws, 76.

Experiment, a means of acquiring experience, 76.

Utility of, 151.

Facts, the observation of, 118.

Faujas de St. Fond, imaginary craters of, 131.

Fluids, laws of the motion of, 181.

Compressibility of, 225.

Consideration of the motions of, more complicated than that of

equilibrium, 235.

Force, analysis of, 86.

The cause of motion, 149.

Phenomena of, 221.

Molecular forces, 245.

Fourier, baron, his opinion that the celestial regions have a

temperature, independent of the sun, not greatly inferior

to that at which quicksilver congeals, 157.

His analysis of the laws of conduction and radiation of heat, 317.

Franklin, Dr., his experiments on electricity, 332.

Fresnel, M., his mathematical explanation of the phenomena of double

refraction, 32.

His improvement on lenses for lamps of lighthouses, 56.

His opinions on the nature of light, 207.

His experiments on the interference of polarized light, 261.

His theory of polarization, 262.

Friction, a source of heat, 313.

Galileo, celebrity of, for his knowledge of science, 72.

His exposition of the Aristotelian philosophy, 110.

His refutation of Aristotle’s dogmas respecting motion, his

persecution in consequence of it, 113.

His knowledge of the accelerating power of gravity, 168.

His knowledge of the weight of the atmosphere, 228.

Galvani, utility of his discoveries in electricity, 335.

His application of it to animals, 336.

Gay-Lussac, his examination of gases and vapours, 319.

Generalization, inductive, 1, 90.

Geology, 281.

Its rank as a science, 287.

Geometry, axioms of, an appeal to experience, not corporeal, but

mental, 95.

Gilbert, Dr., of Colchester, his knowledge of magnetism and

electricity, 112.

Gravitation, law of, a physical axiom of a very high and universal

kind, 98.

Influence of, decreases in the inverse ratio of the square of the

distance, 123.

Greece, philosophers of, their extraordinary success in abstract

reasoning, and their careless consideration of external

nature, 105.

Their general character, 106.

Philosophy of, 108.

Grimaldi, a jesuit of Bologna, his discovery of diffraction, or

inflection of light, 252.

Guinea and feather experiment, 168.

Gunpowder, invention of, 55.

A mechanical agent, 62.

Haarlem lake, draining of, 61.

Harmony, sense of, 248.

Head, captain, anecdote of, 84.

Heat, 193.

Radiation and conduction of, 205.

One of the chief agents in chemistry, 310.

Our ignorance of the nature of, 310.

Abuse of the sense of the term, 311.

The general heads under which it is studied, 312.

Its most obvious sources, 312.

Animal heat, to what process referable, 313.

Radiation and conduction of, 314.

Solar heat differs from terrestrial fires, or hot bodies, 315.

Principal effects of, 317.

The antagonist to mutual attraction, 322.

Latent heat, 322.

Specific heat, 323.

Herschel, sir William, his analysis of a solar beam, 314.

Hipparchus, his catalogue of stars, 276.

Holland drained of water by windmills, 61.

Hooke almost the rival of Newton, 116.

Huel Towan, steam-engine at, 59.

Huyghens, his doctrine of light, 207.

Ascertains the laws of double refraction, 254.

Hydrostatics, first step towards a knowledge of, made by

Archimedes, 231.

Law of the equal pressure of liquids, 232.

General applicability of, 232.

Hypothesis, not to be deterred from framing them, 196.

Conditions on which they should be framed, 197.

Illustrated by the laws of gravitation, 198.

Use and abuse of, 204.

Induction, different ways of carrying it on, 102.

Steps by which it is arrived at on a legitimate and extensive

scale, 118.

First stage of, 144.

Verification of, 164.

Instanced in astronomy, 166.

Must be followed into all its consequences, and applied to all those

cases which seem even remotely to bear upon the subject of

enquiry, 173.

Nature of the inductions by which quantitative laws are arrived

at, 176.

Necessity of induction embracing a series of cases which absolutely

include the whole scale of variation of which the quantities

in question admit, 177.

Induced electricity, 333.

Inertia, 223.

Iodine, discovery of, 50.

Efficacy of, in curing goître, 51.

Isomorphism, law of, 170.

Kepler, effect of his discoveries on the Aristotelian philosophy, 113.

Nature of his laws of the planetary system, 178.

Proofs of the Newtonian system, 179.

Knowledge, physical facts illustrative of the utility of, 45.

Diffusion of, how to take advantage of in the investigation of

nature, 138.

Lagrange, his improvements on Newton’s theory of sound, 247.

His astronomical researches, 275.

Lamp, safety, 55.

Laplace, his explanation of the residual velocity of sound and

confirmation of the general law of the developement of heat

by compression, 172.

His astronomical research, 275.

His experiments on the dilatation of bodies by heat, 319.

His study of specific heat, 323.

Latent heat, 323.

Laws, inductive, 171.

General, 198.

How applicable, 199.

Illustrated by the planetary system, 201.

Empirical laws, 178.

Lavoisier, his improvements in chemical science, 302.

Experiments on dilatation of bodies by heat, 319.

His investigation on specific heat, 323.

Light, refraction of, 30.

Double refraction of, 31.

Polarization of, 254.

Light and vision, ignorance of the ancients respecting, 249.

Lighthouse, 56.

Lightning, how to judge philosophically of it, 120.

Returning stroke of, 121.

Liquids, cohesion, attraction and repulsion of the particles of, 227.

Differ from aëriform fluids by their cohesion, 233.

The Florentine experiment on; experiments by Canton, Perkins,

Oërsted, and others on, 235.

Obscurity of the laws of dilatation of, 320.

Linnæus, his knowledge of crystalline substances, 239.

Logic, 19.

Lyell’s Principles of Geology, extract from, 146.

Magnetism may be caused by electricity, 93.

Offers a “glaring instance” of polarity, 326.

Experiments illustrative of, 327.

Malus, a French officer of engineers, discovers the polarization of

light, 132, 258.

Man, regarded as a creature of instinct, 1.

Of reason and speculation, 3.

His will determined by causes and consequences, 6.

Advantages to, from the study of science, 7.

His necessity to study the laws of nature illustrated, 66.

Happiness and the opposite state of man in the aggregate, 67.

Advantages conferred on, by the augmentation of physical

resources, 68.

Advantages from intellectual resources, 69.

Mariotte, his law of equilibrium of an elastic fluid recently verified

by the Royal Academy of Paris, 231.

His difference between solar and other heat, 315.

Matter, indestructibility of; Divided by grinding, 40.

By fire, 41.

Dilated by heat, 193.

Inertia of, 202.

Polarity of, one of the ultimate phenomena to which the analysis of

nature leads us, 245.

Inherent activity of, 297.

Causes of the polarity of, 299.

Imponderable forms of, 310.

Measure, the standard, difficulty of preserving it unaltered, 128.

How to be assisted in measurement, 129.

Our conclusions from, should be conditional, 130.

Menai Bridge, weight and height of, 60.

Mechanics, practical, 63.

Mètre, the French, 126.

Microscopes, power of, 191.

Millstones, method of making in France, 48.

Mind, its transition from the little to the great, and _vice versâ_,

illustrated, 172.

Mineralogy unknown to the ancients, 79.

Prejudiced by the rage for nomenclature, 139.

Benefited by the progress of chemical analysis, 293.

Minerals, simple, apparent paucity of, 294.

Difficulty in classing them, 295.

Mitscherlich, his law of isomorphism, 170.

His experiments on the expansion of substances by heat, 243.

Motion, 87.

Simplicity and precision of the laws of, 179.

Nature, laws of, 37.

Immutability of, 42.

Harmony of, and advantage of studying them, 43.

Prove the impossibility of attaining the declared object of the

alchemist. How they serve mankind generally, 44.

Illustrated by mining, 45.

Economy derived from a knowledge of, 65.

How to be regarded, 100, 101.

Nature, objects of, an enumeration and nomenclature of, useful in the

study of, 135.

Mechanism of, on too large or too small a scale to be immediately

cognisable by our senses, 191.

Newton, his proof of Galileo’s laws of gravitation by an experiment

with a hollow glass pendulum, 160.

His foundation to hydrodynamical science, 181.

Fixes the division between statics and dynamics, 223.

His investigation of the law of equilibrium of elastic fluids, 231.

His law of hydrostatics, 232.

His foundation of hydrodynamics 236.

His analysis of sound, 247.

Hypothesis of light, 250.

Examination of a soap-bubble, 252.

His hypothesis of fits of easy transmission and reflection, 253.

His combination of mathematical skill with physical research, 271.

His Principia, 272.

His successors; his geometry, 273.

Nomenclature, importance of, to science, 136.

More a consequence than a cause of extended knowledge, 138.

Prejudicial to mineralogy, 139.

Norman, Robert, his discovery of the dip of the needle, 327.

Numerical precision, necessity of, in science, 122.

Objects, and their mutual actions, subjects of contemplation, 118.

Observation, a means of acquiring experience, 76.

Passive and active, 77.

Recorded observation, 120.

Necessity of, to acquire precise physical data, 215.

Illustrated by the barometer, 216.

Oërsted, his discoveries in electricity and magnetism, 132.

Of electro-magnetism, 340.

Opacity, 189.

Otto von Guericke of Magdeburgh, his invention of the air-pump, 230.

Paracelsus, power of his chemical remedies; his use of mercury,

opium, and tartar, 112.

Pascal, his crucial instances proving the weight of air, 229.

Pendulum, 126.

Phenomena, analysis of, illustrated by musical sounds, the sensation

of taste, 85.

The ultimate and inward process of nature in the production of, 86.

Analysis of complex phenomena, 88.

Ultimate phenomena, 90.

How the analysis of, is useful, 97.

A transient phenomenon, how to judge of, 122.

Method of explaining one when it presents itself, 148.

How to discover the cause of one, 150.

Two, or many, theories, maintained as the origin of, in

physics, 195.

Cosmical phenomena, 265.

Philosophy, natural, unfounded objections to the study of, 7.

Advantages derivable from the study of, 10.

Pleasure and happiness, the consequences of the study of, 15.

Phlogistic doctrines of Beccher and Stahl, 300.

Physical data, necessity of, 209.

Great importance of, 211.

Illustrated by the erection of observatories, 213.

Necessity of an exact knowledge of, 214.

More precise than the observations by which we acquire them, 215.

Physics, axioms of; analysis of, 102.

Planets, circumjovial, 186.

Platina, discovery of, 308.

Pliny, his knowledge of quartz and diamond, 239.

Pneumatics, 228.

Political economy, 73.

Prejudices of opinion and sense, 80.

Conditions on which such are injurious, 81.

Illustrated by the division of the rays of light, by the moon at the

horizon, and by ventriloquism, 82.

By the transition of the hand from heat to cold, 83.

Prevost, M., his theory of heat, 316.

His theory of reciprocal interchanges, a proof of the radiation

of cold, 318.

Printing, the art of, 193.

Performed by steam, 194.

Probabilities, doctrine of, 217.

Illustrated by shooting at a wafer, 218.

Prout, Dr., his opinion of the atomic weights, 307.

Pyrometry, 319.

Pythagoras, philosophy of, 107.

Quinine, sulphate of, comparative comfort and health resulting from

the use of, 56.

Radiation of heat, laws of, 205.

Repulsion in fluids and solids, 227.

Rules, general, for guiding and facilitating our search among a great

mass of assembled facts, 151.

Rumford, count, experiments of, on gunpowder, 62.

Savart, M., his experiments on solids, 243.

His researches on sound, 249.

Science, abstract, a preparation for the study of physics, 19.

Not indispensable to the study of physical laws, 25.

Instances illustrative of, 27.

Science, physical, nature and objects, immediate and collateral, as

regarded in itself and in its application to the practical

purposes of life, and its influence on society, 35.

State of, previous to the age of Galileo and Bacon, 104.

Causes of the rapid advance of, compared with the progress at an

earlier period, 347.

Science, natural, cause and effect, the ultimate relations of, 76.

Sciences and Arts, remarks on the language, terms, or signs used in

treating of them, 70.

Receive an impulse by the Baconian philosophy, 114.

Sensation, cause of, 91.

Senses, inadequate to give us direct information for the exact

comparison of quantity, 124.

Substitutes for the inefficiency of, 125.

Seringapatam, method of breaking blocks from the quarries of, 47.

Shells found in rocks at a great height above the sea, supposed

cause of, 145.

Smeaton, his experiments on bodies dilated by heat, 319.

Solids, transparent, exhibit periodical colours when exposed to

polarized light, 99.

Influence of, on the Mind, 101.

Solids in general, nature of, 236.

Constitution of, complicated, 237.

Toughness of, distinct from hardness; tenacity of, 238.

Become liquefied by the addition of heat, 321.

Sounds, musical, illustrative of the analysis of phenomena, 85.

Means of having a knowledge of, 89.

Propagation of, through the air, 246.

Newton’s analysis of, 247.

Standard measurement, necessity of, 125.

Laws of nature used as such, illustrated by the rotation of the

earth, 126.

Substances all subject to dilatation by the addition of heat, 243.

Sun, the character of the heat of, 315.

Thales, philosophy of, 107.

Theories, how to estimate the value of, 204.

Best arrived at by the consideration of general laws, 208.

Explanatory of the phenomena of nature; on what their application

ought to be grounded, 209.

Thomson, Dr., his opinion of the atomic weights, 307.

Thermometer, air, 319.

Thermo-electricity, 341.

Time, division of, 126, 127.

Torricelli, pupil of Galileo, his experiments proving the weight of

atmosphere, 229.

Torpedo, shock of, 341, 342.

Ulugh Begh, his catalogue of stars, 277.

Vaccination, success of, as a preventive to small-pox, 52.

Vision and light, ignorance of the ancients respecting, 249.

Volta, his discoveries in electricity, 335.

Electric pile of, 337.

Voltaic circuit, 338.

Water, effects of the power of, 61.

Whewell, his experiments, 187.

Wells, Dr., his theory of dew, 163.

Wind, effects of the power of, 61.

Wire steel, magnetized masks of, used by needle-makers, 57.

Wollaston, Dr., his verification of the laws of double refraction in

Iceland spar, 258.

His invention of the goniometer, 292.

World, the materials of the, 290.

Young, Dr., his experiments on the interference of the rays of

light, 260.

Zoology, fossil, 344.

THE END.

LONDON

PRINTED BY SPOTTISWOODE AND CO.

NEW-STREET SQUARE.

FOOTNOTES

[1] Hooke’s Posthumous Works. Lond. 1705.--p. 472 and p. 458.

[2] Wealth of Nations, book i. chap. i. p. 15.

[3] On this subject, we cannot forbear citing a passage from one of

the most profound but at the same time popular writers of our time, on

a subject unconnected it is true with our own, but bearing strongly

on the point before us. “But, if science be manifestly incomplete,

and yet of the highest importance, it would surely be most unwise

to restrain enquiry, conducted on just principles, even where the

immediate practical utility of it was not visible. In mathematics,

chemistry, and every branch of natural philosophy, how many are the

enquiries necessary for their improvement and completion, which, taken

separately, do not appear to lead to any specifically advantageous

purpose! how many useful inventions, and how much valuable and

improving knowledge, would have been lost, if a rational curiosity,

and a mere love of information, had not generally been allowed to be a

sufficient motive for the search after truth!”--Malthus’s Principles of

Political Economy, p. 16.

[4] Λογος, _ratio_, reason.

[5] Λογος, _verbum_, a word.

[6] It were much to be wished that navigators would be more cautious in

laying themselves open to a similar censure. On looking hastily over

a map of the world we see three Melville Islands, two King George’s

Sounds, and Cape Blancos innumerable.

[7] Young. Lectures on Nat. Phil. ii. 627. See also Phil. Trans. 1801-2.

[8] Captain Basil Hall, R. N.

[9] We must caution our readers who would assure themselves of it by

trial, that it is an experiment of some delicacy, and not to be made

without several precautions to ensure success. For these we must refer

to our original authority (Fresnel. Mémoire sur la Diffraction de la

Lumiere, p. 124.); and the principles on which they depend will of

course be detailed in that volume of the Cabinet Cyclopædia which is

devoted to the subject of LIGHT.

[10] Little reels used in cotton mills to twist the thread.

[11] Such a block would weigh between four and five hundred thousand

pounds. See Dr. Kennedy’s “Account of the Erection of a Granite Obelisk

of a Single Stone about Seventy Feet high, at Seringapatam.”--_Ed.

Phil. Trans._ vol. ix, p. 312.

[12] Dr. Coindet of Geneva.

[13] Journal of a Voyage to the South Seas, &c. &c. under the Command

of Commodore George Anson, in 1740-1744, by Pascoe Thomas, Lond. 1745,

So tremendous were the ravages of scurvy, that, in the year 1726,

admiral Hosier sailed with seven ships of the line to the West Indies,

and buried his ships’ companies twice, and died himself in consequence

of a broken heart. Dr. Johnson, in the year 1778, could describe a

sea-life in such terms as these:--“As to the sailor, when you look down

from the quarter deck to the space below, you see the utmost extremity

of human misery, such crowding, such filth, such stench!”--“A ship is

a prison with the chance of being drowned--it is worse--worse in every

respect--worse room, worse air, worse food--worse company!” Smollet,

who had personal experience of the horrors of a seafaring life in those

days, gives a lively picture of them in his Roderick Random.

[14] Lemon juice was known to be a remedy for scurvy far superior

to all others 200 years ago, as appears by the writings of Woodall.

His work is entitled “The Surgeon’s Mate, or Military and Domestic

Medicine. By John Woodall, Master in Surgery London, 1636,” p. 165. In

1600, Commodore Lancaster sailed from England with three other ships

for the Cape of Good Hope, on the 2d of April, and arrived in Saldanha

Bay on the 1st of August, the commodore’s own ship being in perfect

health, from the administration of three table-spoonsfull of lemon

juice every morning to each of his men, whereas the other ships were so

sickly as to be unmanageable for want of hands, and the commander was

obliged to send men on board to take in their sails and hoist out their

boats. (Purchas’s Pilgrim, vol. i. p. 149.) A Fellow of the college,

and an eminent practitioner, in 1753 published a tract on sea scurvy,

in which he adverts to the superior virtue of this medicine; and Mr. A.

Baird, surgeon of the Hector sloop of war, states, that from what he

had seen of its effects on board of that ship, he “thinks he shall not

be accused of presumption in pronouncing it, if properly administered,

a _most infallible remedy_, both in the cure and prevention of

scurvy.” (Vide Trotter’s Medicina Nautica.) The precautions adopted

by captain Cook in his celebrated voyages, had fully demonstrated by

their complete success the practicability of keeping scurvy under in

the longest voyages, but a uniform system of prevention throughout the

service was still deficient.

It is to the representations of Dr. Blair and sir Gilbert Blane, in

their capacity of commissioners of the board for sick and wounded

seamen, in 1795, we believe, that its _systematic introduction into

nautical diet_, by a general order of the admiralty, is owing. The

effect of this wise measure (taken, of course, in conjunction with the

general causes of improved health,) may be estimated from the following

facts:--In 1780, the number of cases of scurvy received into Haslar

hospital was 1457; in 1806 _one_ only, and in 1807 _one_. There are now

many surgeons in the navy who have never seen the disease.

[15] Throughout France the conductor is recognised as a most

valuable and useful instrument; and in those parts of Germany where

thunder-storms are still more common and tremendous they are become

nearly universal. In Munich there is hardly a modern house unprovided

with them, and of a much better construction than ours--several copper

wires twisted into a rope.

[16] We have been informed by an eminent physician in Rome, (Dr.

Morichini) that a vast quantity of the sulphate of quinine is

manufactured there and consumed in the Campagna, with an evident effect

in mitigating the severity of the malarious complaints which affect its

inhabitants.

[17] Dr. Johnson, Memoirs of the Medical Society, vol. v.

[18] The engine at Huel Towan. See Mr. Henwood’s Statement “of the

performance of steam-engines in Cornwall for April, May, and June,

1829.” Brewster’s Journal, Oct. 1829.--The _highest_ monthly average of

this engine extends to 79 millions of pounds.

[19] However, this is not quite a fair statement; a man’s daily labour

is about 4 lbs. of coals. The extreme toil of this ascent arises from

other obvious causes than the mere height.

[20] Its surface is about 40,000 acres, and medium depth about 20 feet.

It was proposed to drain it by running embankments across it, and thus

cutting it up into more manageable portions to be drained by windmills.

[21] No one doubts the _practicability_ of the undertaking. Eight or

nine thousand chaldrons of coals duly burnt would evacuate the whole

contents. But many doubt whether it would be profitable, and some,

considering that a few hundreds of fishermen who gain their livelihood

on its waters would be dispossessed, deny that it would be _desirable_.

[22] “Experiments to determine the Force of fired Gunpowder.” Phil.

Trans. vol. lxxxvii. p. 254. et seq.

[23] See a very ingenious application of this kind in Mr. Babbage’s

article on Diving in the Encyc. Metrop.--Others will readily suggest

themselves. For instance, the ballast in reserve of a balloon might

consist of materials capable of evolving great quantities of hydrogen

gas in proportion to their weight, should such be found.

[24] The sulphuric. Bracconot, Annales de Chimie, vol. xii. p. 184.

[25] D’Arcet, Annales de l’Industrie, Fevrier, 1829.

[26] See Dr. Prout’s account of the experiments of professor Autenrieth

of Tubingen. Phil. Trans. 1827, p. 381. This discovery, which renders

famine next to _impossible_, deserves a higher degree of celebrity than

it has obtained.

[27] Greenwich.

[28] Maskelyne’s.

[29] Thomson’s First Principles of Chemistry, vol. ii. p. 68.

[30] Galileo exposes unsparingly the Aristotelian style of reasoning.

The reader may take the following from him as a specimen of its

quality. The object is to prove the immutability and incorruptibility

of the heavens; and thus it is done:--

I. Mutation is either generation or corruption.

II. Generation and corruption only happen between contraries.

III. The motions of contraries are contrary.

IV. The celestial motions are circular.

V. Circular motions have no contraries.

α. Because there can be but three simple motions.

1. To a centre.

2. Round a centre.

3. From a centre.

β. Of three things, one only can be contrary to one.

γ. But a motion to a centre is manifestly the contrary to a

motion from a centre.

δ. Therefore a motion _round_ a centre (_i. e._ a circular

motion) remains without a contrary.

VI. _Therefore_ celestial motions have no contraries--_therefore_

among celestial _things_ there are no contraries--_therefore_

the heavens are eternal, immutable, incorruptible, and so forth.

It is evident that all this string of nonsense depends on the excessive

vagueness of the notions of generation, corruption, contrariety, &c. on

which the changes are rung.--_See_ GALILEO, _Systema Cosmicum_, Dial.

i. p. 30.

[31] Macquer justly observes, that the alchemists would have rendered

essential service to chemistry had they only related their unsuccessful

experiments as clearly as they have obscurely related those which they

pretend to have been successful.--_Macquer’s Dictionary of Chemistry_,

i. x.

[32] Paracelsus performed most of these cures by mercury and opium,

the use of which latter drug he had learned in Turkey. Of mercurial

preparations the physicians of his time were ignorant, and of opium

they were afraid, as being “cold in the fourth degree.” Tartar was

likewise a great favourite of Paracelsus, who imposed on it that name,

“because it contains the water, the salt, the oil, and the acid, which

burn the patient as hell does:” in short, a kind of counterbalance to

his opium.

[33] See the Life of Galileo Galilei, by Mr. Drinkwater, with

Illustrations of the Advancement of Experimental Philosophy.

[34] The temporary star in Cassiopeia observed by Cornelius Gemma, in

1572, was so bright as to be seen at noon-day. That in Serpentarius,

first seen by Kepler in 1604, exceeded in brilliancy all the other

stars and planets.

[35] Edinburgh Phil. Journ. 1819, vol. i. p. 8.

[36] The abstract principle of repetition in matters of measurement

(viz. juxta-position of units without error) is applicable to a great

variety of cases in which quantities are required to be determined to

minute nicety. In chemistry, in determining the standard atomic weights

of bodies, it seems easily and completely applicable, by a process

which will suggest itself at once to every chemist, and seems the only

thing wanting to place the exactness of chemical determinations on a

par with astronomical measurements.

[37] Accurate and _perfectly_ authentic copies of the yard and pound,

executed in platina, and hermetically sealed in glass, should be

deposited deep in the interior of the massive stone-work of some great

public building, whence they could only be rescued with a degree

of difficulty sufficient to preclude their being disturbed unless

on some very high and urgent occasion. The fact should be publicly

recorded, and its memory preserved by an inscription. Indeed, how much

valuable and useful information of the actual existing state of arts

and knowledge at any period might be transmitted to posterity in a

distinct, tangible, and imperishable form, if, instead of the absurd

and useless deposition of a few coins and medals under the foundations

of buildings, specimens of ingenious implements or condensed statements

of scientific truths, or processes in arts and manufactures, were

substituted. Will books infallibly preserve to a remote posterity all

that we may desire should be hereafter known of ourselves and our

discoveries, or all that posterity would wish to know? and may not a

useless ceremony be thus transformed into an act of enrolment in a

perpetual archive of what we most prize, and acknowledge to be most

valuable?

[38] In the system alluded to, the name of quartz is assigned to

iolite and obsidian; that of mica to plumbago, chlorite, and uranite;

sulphur, to orpiment and realgar, &c. See Mohs’s System of Mineralogy,

translated by Haidinger.

[39] The following passage, from Lindley’s Synopsis of the British

Flora, characterises justly the respective merits, in a philosophical

point of view, of natural and artificial systems of classification

in general, though limited in its expression to his own immediate

science:--“After all that has been effected, or is likely to be

accomplished hereafter, there will always be more difficulty in

acquiring a knowledge of the natural system of botany than of the

Linnæan. The latter skims only the surface of things, and leaves the

student in the fancied possession of a sort of information which it is

easy enough to obtain, but which is of little value when acquired: the

former requires a minute investigation of every part and every property

known to exist in plants; but when understood has conveyed to the mind

a store of real information, of the utmost use to man in every station

of life. Whatever the difficulties may be of becoming acquainted with

plants according to this method, they are inseparable from botany,

which cannot be usefully studied without encountering them.” Schiller

has some beautiful lines on this, entitled “Menschliches Wissen” (or

Human Knowledge); Gedichte, vol. i. p. 72. Leipzig, 1800.

[40] Lyell’s Principles of Geology, vol. i. Fourrier, Mém. de l’Acad.

des Sciences, tom. vii. p. 592. “L’établissement et le progrès des

sociétés humaines, l’action des forces naturelles, peuvent changer

notablement, et dans de vastes contrées, l’état de la surface du sol,

la distribution des eaux, et les grands mouvemens de l’air. De tels

effets sont propres à faire varier, dans le cours de plusieurs siècles,

le dégré de la chaleur moyenne; car les expressions analytiques

comprennent des coefficiens qui se rapportent à l’état superficiel,

et qui influent beaucoup sur la valeur de la température.” In this

enumeration, by M. Fourrier, of causes which may vary the general

relation of the surface of extensive continents to heat, it is but

justice to Mr. Lyell to observe, that the gradual shifting of the

_places_ of the continents themselves on the surface of the globe,

by the abrading action of the sea on the one hand, and the elevating

agency of subterranean forces on the other, does not expressly occur

and cannot be fairly included in the general sense of the passage,

which confines itself to the consideration of such changes as may take

place on the existing surface of the land.

[41] The reader will find this subject further developed in a paper

lately communicated to the Geological Society.

[42] Phil. Trans. 1824.

[43] Wells on Dew.

[44] Principia, book iii. prop. 6.

[45] A very curious instance of the pursuit of a law completely

empirical into an extreme case is to be found in Newton’s rule for

the dilatation of his coloured rings seen between glasses at great

obliquities. Optics, book ii. part i. obs. 7.

[46] See Phil. Trans. 1819.

[47] “When we are told that Saturn moves in his orbit more than 22,000

miles an hour, we fancy the motion to be swift; but when we find that

he is more than three hours moving his own diameter, we must then think

it, as it really is, slow.” Thirty Letters on various Subjects, by

William Jackson, 1795.

[48] Thomson’s First Principles of Chemistry.

[49] There seems no doubt, however, that an achromatic telescope had

been constructed by a private amateur, a Mr. Hall, some time before

either Euler or Dollond ever thought of it.

[50] We allude to the recently invented achromatic combinations of

Messrs. Barlow and Rogers, and the dense glasses of which Mr. Faraday

has recently explained the manufacture in a memoir full of the most

beautiful examples of delicate and successful chemical manipulation,

and which promise to give rise to a new era in optical practice, by

which the next generation at least may benefit. See Phil. Trans. 1830.

[51] Alphonso of Castile, 1252.

[52] Jackson, Letters on Various Subjects, &c.

[53] Thomson’s First Principles of Chemistry, Introduction.

[54] The progress of astronomical discovery has since shown that this

law cannot be relied on (1851).

[55] Novum Organum, part ii. table 2. (24), (30), &c. on the form or

nature of heat.

[56] We will mention one which we do not remember to have seen

noticed elsewhere in the case of a disturbance of the equilibrium of

heat produced by means purely mechanical, and by a process depending

entirely on a certain order and sequence of events, and the operation

of known causes. Suppose a quantity of air enclosed in a metallic

reservoir, of some good conductor of heat, and suddenly compressed by

a piston. After giving time for the heat developed by the condensation

to be communicated from the air to the metal which will be thereby

more or less raised in temperature _above_ the surrounding atmosphere,

let the piston be suddenly retracted and the air restored to its

original volume in an instant. The whole apparatus is now precisely in

its initial situation, as to the disposition of its material parts,

and the whole quantity of heat it contains remains unchanged. But it

is evident that the distribution of this heat within it is now very

different from what it was before; for the air in its sudden expansion

cannot re-absorb in an instant of time all the heat it had parted with

to the metal: it will, therefore, have a temperature _below_ that of

the general atmosphere, while the metal yet retains one above it. Thus,

a subversion of the equilibrium of temperature has been _bonâ fide_

effected. Heat has been driven from the air into the metal, while every

thing else remains unchanged.

We have here a means by which, it is evident, heat may be obtained, to

any extent, from the air, without fuel. For if, in place of withdrawing

the piston and letting the _same_ air expand, within the reservoir, it

be allowed to escape so suddenly as not to re-absorb the heat given

off, and fresh air be then admitted and the process repeated, any

quantity of air may thus be _drained_ of its heat.

[57] See Phil. Trans. 1824.

[58] If the brain be an electric pile, constantly in action, it may be

conceived to discharge itself at regular intervals, when the tension

of the electricity developed reaches a certain point, along the nerves

which communicate with the heart, and thus to excite the pulsations of

that organ. This idea is forcibly suggested by a view of that elegant

apparatus, the dry pile of Deluc; in which the successive accumulations

of electricity are carried off by a suspended ball, which is kept by

the discharges in a state of regular pulsation for any length of time.

We have witnessed the action of such a pile maintained in this way for

whole years in the study of the above-named eminent philosopher. The

same idea of the cause of the pulsation of the heart appears to have

occurred to Dr. Arnott; and is mentioned in his useful and excellent

work on physics, to which however, we are not indebted for the

suggestion, it having occurred to us independently many years ago.

[59] See a description of a contrivance of this kind by Dr. Young,

Lectures, vol. i. p. 191.

[60] Boyle’s Works, folio, vol. iii. Essay x. p. 185.

[61] Jackson, The Four Ages, p. 52. London: Cadell and Davies, 1798.

8vo.

[62] Jackson, The Four Ages, p. 90.

Transcriber’s Notes

Cover created by Transcriber and placed in the Public Domain.

Punctuation, hyphenation, and spelling were made consistent when a

predominant preference was found in this book; otherwise they were not

changed.

Simple typographical errors were corrected; occasional unbalanced

quotation marks retained.

Ambiguous hyphens at the ends of lines were retained.

Spelling of non-English words was not reviewed.

Text uses both “appreciate” and “appretiate”; both retained.

Index not checked for proper alphabetization or correct page references.