>. 
of Muriatic Acid and Water. 73 
into a frame in the manner already described. 
One of these was flint glass, the focal dis- 
tance 103 inches; that of the other (which 
was of crown glass) 93; of the two together 
53, inches. The following table shews the 
results obtained with these lenses; and being 
similar to the above, needs no further expla- 
nation. 
Liquits PP recat aa PRS dict 
Water ...... ncRNA 1.00 9 aaa .00 
Do. pith acid. 1.07 90 1.07 
Miatibtio cia gor 117. oth Btn: OT 
These results are similar to the former; 
the acid used in either case was not highly 
concentrated, but such as I was able to pro- 
cure at the times the experiments were made; 
there can however, I think, be no doubt, on 
inspection of the preceding tables, but that 
the refractive power would increase (so that 
the focal distances would continue to be pro- 
portional to the specific gravity ) with the den- 
sity of the acid. 
Conceiving that the other mineral acids 
might have these properties in common with 
the muriatic, I made a trial of them, using 
the glass lenses last mentioned, when the 
VOL. IIt. K 
