72 On the Refractive Powers - 
of the observed focal distances of the com- 
pound lens when containing these different 
portionsof acid, &c. The fourth column is 
obtained from the third by calculation, bemg 
proportional to it; for instance, as the num- 
ber opposite to water, 285, is to 1, (the 
Specific gravity of water,) so is any other 
number in colunm 8, to the specific gravity of 
the sicher pcm 8 reset _ 1 needs 
no remark. 
~itO) 
p. Gr. aad 
_ Sp- Gr, per 
Expt. "Focal dist. Folin focet dia 
I Liquids 
a 
& 30 
WATER cc eset cesennws 1.000 
Do. witha littleacid) 1.055" © 
Do. with more e acid | "087 35.70" mer 
Do, do. doi ah : Sh12L * | 
Do.) do. do. sses0s] 9 1.1465 "27.00 Jo 1.58850: 
cd i al erpcty remy, Sai yi T8007 1.180°° | 
. = ene 
19c ti HIiLZ i Olio; St FE 
coment vn eben pi sie 
other from the) theory, differ from one ano- 
ther in no instance so much as one per cent, 
and correspond as nearly as can be expected. 
I have lately repeated some of these expe- 
riments, making use of different lenses. set 
