of Muriatic Acid and Water. 71 
These facts were ascertained by introducing 
a portion of the fluid betwixt two double- 
convex lenses. of .crown. glass; these: were 
cemented into .a frame, for the twofold: pur- 
pose of holding: them steady, and of contain- 
ing the'acid, &c. to’be experimented upon, sto 
leave room for which the lenses were separated 
about 3, of. ‘aninch. By this means a double 
concave lens of the fluid was obtained, and its: 
less, or greater refractive power, lessened,: 
or increased the focal distance of the com- 
pound lens, (the refractive power of the glass 
lenses being uniform, the results are not shaxit 
fected thereby.) whey 
The focal distances of the a lenses were 
about 24 and 27 inches respectively; when 
placed together i in the frame, about 13; when. 
the space betwixt was filled with water, 
nearly 24; and’'when muriatic acid was intro“ 
duced, the focal distance, was 28 inches, ,. , 
The following table is the result of experi- 
ments made’ with muriatic acid’of the specific 
gravity 1.177, and with portions of 'the same’ 
diluted ‘with ‘water; and‘ with! water alone: 
The specific gravities of each fluid were taken’ 
in the usual way by weighing’& small bottle’ 
full of each, and which contained just 1000 
grains of water; these occupy the second co- 
lumn of the table; the third ‘column consists 
