considered only in relation to practice, and Bacon does not so much as
mention their infinitely greater importance in the theoretical part of
induction. The important law of gravitation in physical astronomy could
never have been demonstrated but by such observations and experiments
as assigned accurate geometrical measures to the quantities compared.
It was necessary to determine with precision the demi-diameter of the
earth, the velocity of falling bodies at its surface, the distance of
the moon, and the speed with which she describes her orbit, before the
relation could be discovered between the force which draws a stone to
the ground and that which retains the moon in her sphere.
In many cases the result of a number of particular facts, or the
collective instances rising out of them, can only be discovered by
geometry, which so far becomes necessary to complete the work of
induction. For instance, in the case of optics, when light passes from
one transparent medium to another, it is refracted, and the angle
which the ray of incidence makes with the superficies which bounds the
two media determines that which the refracted ray makes with the same
superficies. Now, all experiment can do for us in this case is, to
determine for any particular angle of incidence the corresponding angle
of refraction. But with respect to the general rule which in every
possible case deduces one of these angles from the other, or expresses
the constant and invariable relation which subsists between them,
experiment gives no direct information. Geometry must, consequently,
be called in, which, when a constant though unknown relation subsists
between two angles, or two variable qualities of any kind, and when
an indefinite number of values of those quantities are assigned,
furnishes infallible means of discovering that unknown relation either
accurately or by approximation. In this way it has been found, when
the two media remain the same, the cosines of the above-mentioned
angles have a constant ratio to each other. Hence, when the relations
of the simple elements of phenomena are discovered to afford a general
rule which will apply to any concrete case, the deductive method must
be applied, and the elementary principles made through its agency to
account for the laws of their more complex combinations. The reflection
and refraction of light by the rain falling from a cloud opposite to
the sun was thought, even before Newton’s day, to contain the _form_ of
the rainbow. This philosopher transformed a probable conjecture into
a certain fact when he deduced from the known laws of reflection and
refraction the breadth of the colored arch, the diameter of the circle
of which it is a part, and the relation of the latter to the place
of the spectator and the sun. Doubt was at once silenced when there
came out of his calculus a combination of the same laws of the simple
elements of optics answering to the phenomena in nature.--_Ed._
[151] As far as this motion results from attraction and repulsion, it
is only a simple consequence of the last two.--_Ed._
[152] These two cases are now resolved into the property of the
capillary tubes and present only another feature of the law of
attraction.--_Ed._
[153] This is one of the most useful practical methods in chemistry at
the present day.
[154] See Aphorism xxv.
[155] Query?
[156] Observe this approximation to Newton’s theory.
[157] Those differences which are generated by the masses and
respective distances of bodies are only differences of quantity, and
not specific; consequently those three classes are only one.--_Ed._
[158] See the citing instances, Aphorism xl.
[159] Aristotle’s doctrine, that sound takes place when bodies
strike the air, which the modern science of acoustics has completely
established, was rejected by Bacon in a treatise upon the same subject:
“The collision or thrusting of air,” he says, “which they will have to
be the cause of sound, neither denotes the form nor the latent process
of sound, but is a term of ignorance and of superficial contemplation.”
To get out of the difficulty, he betook himself to his theory of
spirits, a species of phenomena which he constantly introduces to give
himself the air of explaining things he could not understand, or would
not admit upon the hypothesis of his opponents.--_Ed._
[160] The motion of trepidation, as Bacon calls it, was attributed
by the ancient astronomers to the eight spheres, relative to the
precession of the equinoxes. Galileo was the first to observe this kind
of lunar motion.--_Ed._
[161] Part of the air is expanded and escapes, and part is consumed
by the flame. When condensed, therefore, by the cold application,
it cannot offer sufficient resistance to the external atmosphere to
prevent the liquid or flesh from being forced into the glass.
[162] Heat can now be abstracted by a very simple process, till the
degree of cold be of almost any required intensity.--_Ed._
[163] It is impossible to compare a degree of heat with a degree of
cold, without the assumption of some arbitrary test, to which the
degrees are to be referred. In the next sentence Bacon appears to have
taken the power of animal life to support heat or cold as the test, and
then the comparison can only be between the degree of heat or of cold
that will produce death.
The zero must be arbitrary which divides equally a certain degree of
heat from a certain degree of cold.--_Ed._
[164] It may often be observed on the leaves of the lime and other
trees.
[Transcriber’s Notes:
Punctuation errors were corrected.
Inconsistent hyphenation was retained.
“De la Lande” and “La Lande” both appear in text and were retained.
“Shenier”, editor’s spelling of “Scheiner”, was retained.
On p. 37, a paragraph break was inserted before "There is a clear
example ...".
On p. 44, “the” was changed from “The” (the usual method).
On p. 85, “that” was changed from “That” (that a species).
On p. 86, “that” was changed from “That” (that an instrument).
On p. 118, “aëriform” was changed from “aeriform” (aëriform or
igniform).
On p. 178, “borrow” was changed from “brorrow” (to borrow a term
from the grammarians).
On p. 204, “sufficiently” was changed from “sufficietly” (but
sufficiently dense).
On p. 219, “quantity” was changed from “quanity” (quantity of gold).
In footnote [5], “psychological” was changed from “pyschological”
(most other psychological).
In footnote [23], “that” was changed from “tha” (that we have
nothing).
In footnote [33], "72" was changed from “22” (Acad. Prior. ii. 72.).
In footnote [60], “ix.” was changed from “x.” (Livy, lib. ix.).
In footnote [71], “οὐσία” was changed from “οὐδία”.
In footnote [86], “necessary” was changed from “necesary” (necessary
to invent).
In footnote [87], “liquor” was changed from “liqour” (the liquor
rose).
In footnote [161], “the” was changed from “th” (by the flame).]