PREF ACE. Vil 
the magnet, timidly attempted a mere coaft- 
ang navigation ; while we, better informed of 
the uies of it, traver{e the wideft oceans, and 
by: the difeovery of the new world, have layed 
open to fcience, aninexhauftible fund of matter. — 
The rife and progres of : medicine, kept Pace 
with the advancement of this moft important 
difcovery ; and tho’ neceflity was the parent of 
the mechanic arts, yet they alfo throve, and 
grew to maturity, under the fame influence. 
Many more inftances might be added to 
this brief view of the utility of natural know- 
ledge; but we thall only give fome of its ufes 
in the polite arts, which have hitherto been 
too little connected with it. 
‘Toinftance particularly 1 in painting, its ufes 
are very extenfive: the permanency of colors 
depends « on.the goodnefs of the pigments; but 
ithe various animal, vegetable, and foffil fubftan- 
ces (out of which they are made) can only be 
known by repeated trials; yet the greateft 
artifts have failed in this refpe@t: the 
fhadows of the divine Raphael have acquired 
an uniform blacknefs, which obfcures the 
finett productions of his pencil, while the 
paintings of Holbein, Durer, and the Venetian- 
School, (who. were admirably {killed in the 
knowledge of pigments) ftill exift in their 
‘primitive frethnefs. 
. But thefe advantages are fmall, compared 
to thofe derived from the knowledge of na- 
ture in the reprefentation of objects: painting 
#8 an imitation of nature; now, who can imi- 
tate without confulting the original? but to 
A 4 come 
