1912] 
cork fl-- 
mer:---- 
Ir. Ir. ; Ir. wr. 
G H 
Fig. F. Diagram of 
thermo-electrie regulator 
used in the constant-tem- 
perature box. Only a part 
of the glycerine-filled tube 
(glyc.) is shown, the rest 
may be seen in plates 16 
and 17. X &%. 
Figs. G and H. Top 
and end views, respectively, 
of the lever. x 14. 
cork fl., cork float; glyc., 
glycerine-filled tube; Ir, 
lever attached to upper end 
of Ir. wr.; sl. wr., slender 
wire between lever and 
float; mer., mereury-filled 
U-tube; Ur. wr., ct. wr., 
heavy wires earrying at 
their lower ends binding 
posts and at their upper 
ends the lever and _ plati- 
num contacts respectively ; 
vial, glass vial. 
Long: Living Eggs of Rats and Mice 
115 
sheet copper shaped and bent as shown 
in figures F, G and H. At the free 
end of the lever is soldered a bit of 
platinum wire, which may touch a 
small plate of platinum soldered to 
the upper end of the other heavy wire 
(ct. wr.) 
contact. 
and thus make an electric 
At the middle point of the 
lever a small hole receives one end of 
a straight piece of slender wire (sl. 
wr.), which hangs down into the regu- 
lator tube. The wire terminates in a 
piece of cork, which fills the tube, but 
without sticking or binding, and rests 
The 
lever and opening into the regulator 
on the surface of the mereury. 
tube may be protected by an inverted 
shell vial (vial) fitted snugly over the 
(cork). 
nected in series with one pair of 
It can easily be adjusted for 
a particular temperature by slipping 
cork The regulator is con- 
lamps. 
the cork (cork) up or down on the 
tube. The operation of the regulator 
depends on the expansion of the glye- 
erine when heated. It will easily be 
seen that when the glycerine expands 
the mercury is foreed down one arm 
of the U and up the one containing 
the cork float, which is thus lifted; 
this breaks the contact at the platinum 
points, thereby shutting off the lamps. 
There are a few precautions which 
should be observed. Too strong a 
current through the regulator is apt 
to cause the points to stick slightly, 
thus causing a variation in tempera- 
ture. This can be avoided by using 
