Elements of the philosophy of the human mind. By Dugald Stewart. Rev. and abridged, with critical and explanatory notes, for the use of colleges and schools. By Francis Bowen ...

302 MEM3ORY
mercury, excepting eight inches, and is inverted, as in the Torricellian experiment, so that the eight inches of common air may
rise to the top; and that I wish to know at what height the
mercury will remain suspenddcl in the tube, the barometer being
at that time twenty-eight inches high. There is here a combination of different laws, which it is necessary to attend to, in
order to be able to predict the result. 1. The air is a heavy
fluid, and the press-ure of the atmosphere is measured by the
column of mercury in the barometer. 2. The air is an elastic
fluid, and its elasticity at the earth's surface (as it resists the
pressure of the atmosphere) is measured by the column of merare for iaed into groups, respecting which a greater number of general propositions can be made, and those propositions more important, than could
be made respecting any other groups into which the same things could be
distributed. The properties, therefore, according to which objects are
classified, should, if possilble, be those which are the causes of many other
properties; or, at any rate, which are sure marks of them.....A
classification thus formed is properly scientific or philosophical, andi is
commonly called a Natural, in contradistinction to a Tccilnical or Arti
ficial, classification or arrangement." Mill's Systemn of Logic, Am. ed. pp.
432-434.
To these excellent remarks of Mr. Mill, it may be added, that writers
even upon the moral sciences, in which classification is less essential as an
aid to the processes of invention and discovery, still strive to assist the
Memory of their readers, and to give a sort of factitious unity to their
otherwise isolated disquisitions, by bringing' forwarld, with undue prolminenee, some one fact or principle, on which all their other speculations
seem to hitch, and which serves, so to speak, as a kind of key-note to the
whole work. Thus, in his Thleory of ]foral Sentisnents, Adam Smith, as
we believe, places more stress upon sympatlzy, and adduces it more frequently to aidl in the explanation of complex moral phenomena, than he
would have cdone for purely philosophical reasons, had he not wished to
give a semblance of harmony andc systematic completeness to his remarks
upon a great variety of subjects. He uses a similar artifice in his great
work upon the TWealth of ~Thationis, in which a great deal more is said about
the clivisionz of labor, than would have appeared necessary, had he not been
anxious to avoid the air of desultory speculation. A more transparent
artifice is often adopted by periodical essayists, like Steele, Swift, Addison,
and Goldsmith, by carrying out the fiction of a club of contributors, or an
imaginary editor, so that rambling essays upon many subjects may have
a slender thread of connection with eacll other. ]