1922] BRIEFER ARTICLES 333 
A SIMPLE sayin FOR CONTROLLING 
TEMPERATURES 
(WITH ONE FIGURE) 
In developing the control equipment for a humidity chamber in 
which it was desired to control temperatures over long periods of time, 
it was found essential to use a temperature control apparatus activated 
by an electric current taken from the ordinary lighting circuit. Trouble- 
some failures with dry cells and storage batteries led to the construction 
ccH 
Toluol 
Fic. 1.—A, binding posts: to which wires from thermostat tube (G) are attached; 
to left-hand binding post (B) i is attached one of the wires leading from heating unit; 
, binding posts to which wires from main lighting circuit are attached (one of the 
wires leading from heating unit is attached to right t-hand 1 post); D, “transformer 
bell” electro 
(to extreme right of armature bar is attached a piece of vabaped heavy « copper wire) ; 
attached to lower part of right-hand magnet is a small piece of rubber cut from a 
rubber stopper, which projects far enough beyond magnet bar to eliminate most 
of the ‘‘chatter” or “buzz”? when coils are operating; 2, two glass vials (0. 75Xt. 5 
inches) partly filled with mercury, into which points of the se copper wire are 
immersed; wires leading from B are in contact with the mercury in vials; F, small, 
3 volt, bell- -ringing, alternating current transformer which furnishes 6, 8, or 14 volts 
as desired (here connected to furnish 8 volts, alternating current); be small single-blade 
knife switch used to test action of coils at D; the asbestos-cover upon which 
units A to F are mounted measures 9.5 11.5 inches, and is designed fot wall attach- 
ment; use of transite board or other insulating material and mounting to reduce fire 
risks is recommended. 
