676 SUMMARY OF CURRENT RESEARCHES RELATING TO 
pieces. By means of the wire /, the tube e is connected with a screw 
arrangement at the base of the tube, so that by turning the milled rim K 
the tube e , with its projecting pieces, can be adjusted in height above 
the end of the tube a. The two projecting pieces serve to conduct the 
heat of the flame, when the lamp is lit, to the tube a, and thence to the 
benzine, so that by adjusting the height of these the heat of the flame is 
regulated. The advantages of the lamp are : — (1) It needs no chimney, 
so that only a very slight move- 
Fig. 98. Fig. 99. ment of the plate of the regu- 
lator is required ; (2) it gives 
no soot ; (3) the size of the 
flame can be easily regulated ; 
(4) the size of the flame once 
regulated remains the same. 
In fig. 97 is shown the 
arrangement of the whole ther- 
mostat. The movable plate, 
13 X 22 cm., rotates about a 
horizontal axis through its 
centre of gravity. The frame 
* on which the thermostat rests 
is supported on four iron feet, 
38 cm. long. The front side 
of the stand is of glass, the 
three others of iron. A space 
at the top of the left side is 
left for the plate, and the right 
side is cut away below for the 
insertion of the lamp. On the 
left side, at a height of 22 cm., 
is a horizontal platform for the 
electromagnet which serves to 
regulate the position of the 
rotating plate. The electro- 
magnet C, with its connections 
with the battery A and current transmitter B, is seen in fig. 98. When 
the current passes the armature D, which is attached to a very flexible 
spring E, is attracted to the magnet. To the free end of the spring is 
attached a thread which passes round a small pulley F, and is fastened 
to the movable plate of the thermostat (fig. 97), above the axis of rota- 
tion. When the armature is drawn towards the magnet, the thread pulls 
the plate so that its lower half covers the flame of the lamp. The tem- 
perature of the thermostat then falls, the current is again broken by the 
automatic regulator B, and the plate is brought back to its original 
position by means of the weak spiral spring beneath the axis (fig. 97). 
The automatic current transmitter is shown in fig. 99. It consists of 
a test-tube containing some mercury, and closed by a good cork, through 
which passes a small tube. The small tube passes down to the bottom 
of the test-tube, and is enlarged at the upper end, where it is closed (but 
not air-tight) by a cork. Through this cork the + wire from the battery- 
passes down to a certain point of the small tube, while the - wire goes 
through the cork of the test-tube down to the mercury at the bottom. 
