226 Prof. Draper’s Deseription of the Tithonomeier. 
A stout tube, six inches long and one tenth of an inch interior © 
diameter, ef, is now fused on at ¢. Its lower end opens into the 
main siphon tube; its upper en ‘is turned over at f, and is nar-_ 
rowed to a fine termination, so as bh to admit a pin, but is not — 
closed. ‘This serves to keep out dust, and in case of a little acid 
passing out, it does not flow over the seale and deface the divis- 
ions. At the back of this tube a scale is is placed, divided into 
Jove abhi Fifty 
ire 7a 2 shows — 
the termination of the narrow tube bent over 7 s 
From a point one fourth of an inch above the a down-— 
wards beyond the bend, and to within half an inch of the w 
z, the whole tube is carefully painted with India ink so as to” 
allow no light to pass; but all the space from a fourth of an inch 
above the stage d to the top of the tube a, is kept as clear and — 
transparent as possible. This portion constitutes the sentient | 
part of the instrument. A light metallic or pasteboard cap, AD, — 
~ fig. 3, closed at the top and open at the bottom, three inches long 4 
and six tenths of an inch in diameter, blackened on its interior, — 
may be dropped over this sentient tube ; it being the office of the 
stage d to receive the lower end of the cap when it is dropped on 
the tube so as to shut out the light. : 
The foot of the instrument k/Z is of brass; it screws into the 
hemispherical block m, which may be insta of hard wood or 
ivory; in this three holes, pqr, are made to serve as mercury 
cups; they should be deep and of small diameter, that the metal : 
may not flow out when it inclines for the purpose of transferring. 
A brass cylindrical cover, LM, LM, may be put over the whole; 
when it is desirable to preserve it in total darkness, it should be — 
blackened without. 
Secondly, of the fluid part—The nid frof-which the mixture 
of chlorine and hydrogen is evolved, and by which it is confined, — 
is yellow commercial mutiatic acid, holding such a quantity of | 
chlorine in solution that it exerts no action on the mixed gases a8 — 
they are produced. From the mode of its preparation igal ways { 
contains a certain quantity of chloride of platina, which gives it 
a deep golden color, a condition of considerable incidental impor- 4 
tance. ‘ 
When muriatic acid is decomposed by voltaic electricity, its : 
chlorine is not evolved, but is taken up in very large quantity au¢ — 
