W. P. Riddell on Soleil's Saccharimeter. 179 
_ The instrument, of which I propose to give a very brief de- 
scription, was brought from Paris by the Hon. J. P. Benjamin, 
of New Orleans, and now belongs to Prof. J. L. Riddell, of the 
University of Louisiana. It consists of the following parts, com- 
mencing at the extremity farthest from the eye of the observer 
when making an analysis :— 
A B ree : 
ae eatE ieee eae 
t——*____]] 4 
, | z h 
Pitta ARR AR AL [AAAAAY) Lbbt AANA 
at thi | 0 ah 0 7 es 
4 ay ——I] ape 
¢ 
= 
_ A, Polarizer, a Nicol’s Prism, admitting only one of the polar- 
zed rays to pass through. 
Depolarizer, being a plate of right-handed quartz, cut per- 
Pendicular to the axis of its crystallization. : 
©, the polarizer proper, or analyzer as related to A and B, 
Whose functions are only to produce any desired tint by merely 
tevolving; which is accomplished by means of a thumb-screw, 
Close to the thumb-screw of the compensator. ; 
D, Biqnartz, composed of two juxtaposed plates of quartz, of 
equal thickness, but of contrary rotative power, one being right- 
Nanded, the other left-handed ; by which the difference observed 
iN the tints of the semi-dises, when the right- and left-handed 
tations in the instrument are not in equilibrio, are doubled, since 
tints as observed through the one semi-disc succeed each 
er in the opposite order to what they do as seen through the 
er, 
E, Tube of o servation, 20 and 22 centimeters long, into 
Whieh the liquid Aa gees is poured, and closed by means 
of glass plates, which are held in their place by brass caps closely 
oth, 
oth 
dud and replaced in its proper position in the instrument, the 
hints of > ap babies Hy a sedinnsy and extraordinary disc 
Will be seen to be different and complementary for the reason al- 
