Heating and Cooling Apparatus for Bimtgen Crystallographic Work. 649 
These steel rods are screwed on to one of the rings, and then quartz tubes 
are slipped over them. 
Spirals of platinum wire are now made and slipped over the quartz 
tubes.* 
The second ring is slipped over the projecting ends of the steel rods, and 
is then screwed down. 
Each spiral is now covered in with kaolin, so that the " turns " are 
electrically insulated. 
Two small holes are drilled through the side of the cylinder and quartz 
tubes inserted in them. 
The drum is now placed inside the cylinder and the free ends of the 
" series wound " spirals passed through the quartz tubes. 
A hole is drilled vertically above the position of the crystal so that a 
a platinum-platinum rhodium thermocouple's junction may be put in contact 
with the crystal. 
The cylinder is now screwed on to an adjustable holder (Fig. 4). 
Two screws, which may slide in slots, enable one to adjust the height of 
the cylinder, whereas two adjusting screws (Fig. 5) allow one to rotate the 
crystals towards or away from the diaphragm. 
The moval^le cone enables the experimenter to rotate the crystal round a 
perpendicular axis.f 
The free ends of the platinum wire are now connected to a pair of well- 
insulated terminals. 
* Nickel wire does not serve this purpose. It generally breaks clown at weak 
points after a few hours. 
t A cylindrical foot piece — like that of the diaiDhragm generally used — would 
allow of an extra rotation. This, however, is hardly necessary, as the cone itself 
allows for small adjustments. 
