4 ON THE ACTION OF TRANSPARENT BODIES 



1. Acetate of Lead, melted. 



A prism of acetate of lead acting in opposition to a prism of 

 crown-glass, produces a considerable secondary spectrum, in 

 which the green fringe is on the same side of the window bar 

 as the vertex of the prism of acetate of lead. This last has 

 therefore a less powerful action on the green rays 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 flint- 

 glass. 



4. Acid, Malic. 



Malic Acid acts more powerfully upon the green rays than 



flint-glass. 



It 



