were still wholly inadequate for philosophical
accuracy. To ascertain quantity, it was necessary to associate number as
the index of precision. Notwithstanding the construction of this
instrument now appears so simple and easy of contrivance, it is only
within a few years that it occurred to fill a tube, having a bulb, with
a fluid; and to note the points at which snow dissolved, and water
boiled: when these were fixed, the intermediate space might form a scale
according to any subdivisions, so as to endow it with precision by the
adjunct of numbers. On many occasions, our sensations deceive us,
especially in a morbid state of the body: a person in the cold stage of
an ague shivers at the temperature that oppresses his attendant with
heat; but the instrument described is subject to no variations, by
marking the gradations of warmth with the definite character of number.
It will now be seen, that man possesses materials for conducting his
reasonings, which animals do not enjoy;--by language, and from his
capacity of numerating. Speech, of course, involves its record, whereby
he can recall the transactions of former ages, and preserve the fruit of
experience for his intellectual nurture, when the tree that produced it
has perished. This record is the elaboration of the hand,--that
wonderful instrument, the register of thought,--that active and and
skilful agent that "turns to shape" the contrivances of the mind.

It is perhaps impossible, in a few words, to describe precisely the
nature of the operation termed reasoning. In general terms it may be
defined, _the means we employ for the attainment of the end proposed;
the employment of knowledge for the discovery of truth_; or _the process
of demonstration_; whether the object be an arithmetical sum, a
geometrical problem, or a discourse on taste. A part of the process of
reasoning, according to received opinion, consists in comparison, either
of things, or of general terms; and this comparison implies not merely
their exterior similitude, but likewise their internal structure and
composition: because two mineral substances may resemble each other in
external appearance, and may wholly differ in their intrinsic
properties. The process of ascertaining wherein they agree, and the
circumstances which discriminate them, is an instance of reasoning, or
the means we employ for the proposed end, and which means necessarily
imply the previous possession of knowledge. It will also be