2."™ . INTRODUCTION. 
other; the cbimBinations or separations which result from the 
general tendency of these moleculesto re- unite; and the 
modifications which. the various circumstances capable of se- 
par ating or approximating them produce on that tendency. It 
is purely a science of expemMenis. and is irreducible to caleu- 
lation. . 
The theory of heat and that of sldbicicity belong either to 
dynamics or chemistry, deaortily to the point of view in 
which they are considered. 
The ruling method in all the branches of general physics 
consists in isolating, bodies, reducing them to their greatest 
simplicity, in bringing each of their properties separately e 
action, either by reflection or “experiment, and by observi S 
or calculating the results; and finally, i in Seneralising and con- 
necting the laws of these properties, so as to form codes, » " 
and, if it were possible, to refer them to.one s single ae 
into which they might all he resolved. ' 
The object of Particular Physics, ov of Ne wtural History ap 
for the terms are synonymous—is the special application of. 
the laws recognised by the various branches of gener hy- J 
Sics to the numerous and varied beings which! ist ff, 
_in order to explain the phenomena which eth of dove. ‘ 
sents. : *, a3 | 
Within this extensive range, astronomy Brod be in: * 
cluded; but that science, sufliciently elucidated by mechanics, 
and inilelidy subjected to its laws, employs methods, differ- 
ing too widely from those required by natural. history, to per- 
mit it to be cultivated by the students of the latter. ' 
Natural history, then, is confined to objects which do not 
allow of exact calculation, nor of precise measurement in all 
their parts. Meteorology also is substracted from it and united 
to general physics; so that, properly speaking, it considers only ~ 
inanimate bodies called minerals, and the different kinds of 
living beings, in all of which we may observe the effects, more 
or less various, of the laws of motion and chemical attraction, 
and of all the other causes analysed by general physics. 
Natural history, in strictness, should employ similar methods 
with the general sciences; and it does so, infact, whenever the- 
