476 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
The electrically heated object-stage consists of the stage proper, 
silver spirals, paraffin oil, an ordinary graduated thermometer, and a 
contact thermometer. There is also a relay (a Neefhammer). The 
object-stage proper is a deep metal box containing a silver spiral con- 
nected with the main current by m 2 n 2 . The regulating apparatus 
consists of a contact thermometer inserted in the stage and the relay 
in a wooden box. The contact thermometer is connected with the relay, 
and closes and opens the current going to the relay from the battery B.* 
The apparatus is worked as follows : — Contact m 2 n 2 is made with 
St the main current, and the current entering by him into the spiral 
heats it. The paraffin thus becomes warmed, and the temperature con- 
tinues to rise until the quicksilver expanding reaches the point of the 
Fig. 84. 
platinum thread t. At this moment the current o q of the element B 
is closed and the hammer A from E. Contact is opened by v p, wffiich, 
in the rest position of the relay, is shut ; and the main current m n , 
m 2 n 2 is opened. No more heat now goes through the spiral, and the 
temperature in the stage sinks. Therefore, when the quicksilver thread 
of the contact thermometer operates, the adjoining current Z S 0 Q is 
opened and the main current again introduced. The alteration of the 
currents is marked by an audible click from the hammer. Only a 
very weak current (0*2 ampere) goes through the spiral. It was found 
possible to regulate the temperature to 0 • 1°, and to keep it constant 
even for a whole day. 
* The contact thermometer is apparently in the \ liquid, and only'itsj extremity 
is visible. This arrangement would allow of the conduction to the liquid of any 
heat which would be generated in the contact thermometer, so tending to counter- 
balance the loss by radiation and keep the paraffin at a constant temperature. — Ed. 
