THE BIOMETER: HOW TO USE IT II5 
closely. The best way to set it up is to mount it per- 
manently, instead of clamping it with several iron 
clamps and stands. The apparatus set up as in Fig. 1 
in the lead frame or in the wooden frame not only looks 
better, but is subject to less damage. 
How to clean the apparatus—The apparatus is con- 
structed and is mounted in such a way that washing and 
cleaning can be done after each experiment without 
taking it apart. Although the procedure of washing 
is exceedingly simple, it is better for the beginner to 
follow exactly the directions given below, for there are 
many stopcocks which have to be turned in a particular 
direction in order to avoid unnecessary accidents which 
sometimes necessitate the expenditure of considerable 
time in bringing the apparatus back into a working con- 
dition. An example will illustrate this: If one forgets 
to turn the stopcock Z during the washing, and the 
space between L and K becomes wet, it will require 
about five or six hours to wash the space and clean and 
dry it. The old saying that an ounce of prevention is 
worth a pound of cure should be borne in mind here. 
Turn the water pump on. Now turn stopcock E 
180° to the right, so that the barium hydroxide solution 
is entirely out of connection with the other two arms of 
the stopcock H. Remove mercury from stoppers S and 
R with a pipette, and then remove the stoppers S and R, 
and tissues if there are any. Turn stopcock Z in such a 
way that the bore inside will look like this 1, thus 
severing the connection between the vertical arm of L 
and the horizontal arms. Turn on stopcocks J and 
Q and F in order. Turn stopcock G go° to the left. 
Withdraw the mercury from chamber A by opening 
