4 ON THE ACTION OF TRANSPARENT BODIES: 
1. Acetate of Lead, melied. 
A prism of acetate of lead acting in opposition to a prism of 
crown-glass, produces a onademile secondary spectrum, in 
which the green fringe is on the same side of the window bar 
as the vertex of the ere of acetate of lead. This last has 
therefore a less powerful action on the green ee than crown- 
glass. 
_ A prism of acetate of lead acting in opposition to flint-glass, 
produces a less secondary spectrum, but the green fringe is 
still on the same side of the bar. 
Owing to the imperfection of the image, I was not able to 
compare this substance with bodies of a higher dispersive 
power, as the secondary spectrum became too small. 
2. Acid, Acetic. 
The acetic acid acts more powerfully upon the green rays 
than flint-glass. 
It acts a little more powerfully upon the green rays than 
crown-glass. 
It acts less powerfully upon the green rays than rock-cry-+ 
stal. 
It acts a little less powerfully upon the green rays than mu- 
riatic acid ; but it is very difficult, in this case, to perceive the 
secondary spectrum. 
3. Acid, Citric. 
Citric Acid acts more powerfully upon green light than flini- 
glass. 
4. Acid, Malic. 
Malic Acid acts more powerfully upon the green rays than 
flint-glass. 
It 
