AFFINITY. 
present are necessary for the practice of chemistry ; it 
would enable us to apply the science with more effect 
to the arts and manufactures; it would enable us to 
trace the chemical changes which are going on in the 
atmosphere and the earth to their origin, and to fore 
see the future changes to which they are liable; and 
thus to form what has hithèrto been attempted in vain, 
a complete theory of meteorology and geology. 
Unfortunately the efforts of philosophers to establish 
these general principles have not hitherto been attend 
ed with complete success ; partly owing to the difficul 
ty of the subject, and partly to the unaccountable ne 
gligence of the greater number of chemists who have 
been more anxious to ascertain particular facts than to 
investigate general principles, and who have often seem 
ed to look upon general principles as altogether foreign 
to their science. Happily this has not been the case 
with all chemists. Several, and these the most illus 
trious, have carefully classified the phenomena, and re 
ferred them under general heads ; and if they have not 
succeeded in discovering laws sufficiently comprehen 
sive to include all the chemical phenomena, have at 
least pointed out several pretty general ones, from the 
knowledge of which the mutual action of many bodies 
on each other may, in not a few cases, be foreseen, even 
prior to experiment. Among these philosophers, none 
stands higher than Bergman, who was not less distin 
guished by his industry and enthusiasm, than by his 
enlarged views and the happy acuteness with which he 
drew general conclusions. To Black and Lavoisier we 
are indebted for two of the most general and most im 
portant laws hitherto discovered in chemistry. Much 
has been done by Kirwan, whose profound knowledge, 
13 
135 
Bok II. 
Still imper 
fectly 
known,