Heating and Coolhig Ai)])aratus for Rimtgen Crystallographic Work. 651 
This apparatus allows one to heat crystals up to 600° C. without any 
trouble.* 
Construction of Cooling Apparatus. 
The absorption of Eontgen rays in liquids is so great that the exposures 
must be continued for many hours before a trace of a photogram can be 
obtained. 
To avoid absorption, four concentric semi-cylinders are soldered on to 
two pieces of rectangular copper plates (Fig. 6). 
The space between the cylinders is packed with asbestos wool. 
The foot piece of the cylinders consists of two pairs semi-circular discs of 
copper. The space between each pair is also packed with asbestos. 
At a central point below the middle of the cylinders a cone is inserted 
(Figs. 7 and 8) in each pair of cylinders, opening 5 mm. 
The upper part of the cylinders is closed by a thin plate of copper. 
The apparatus is mounted on its carrier, which is similar to carrier of 
the oven. 
The screw, a, enables one to alter the height of the crystal, which is 
clamped between the cones. 
The whole of the apparatus nickel-plated and polished. 
This apparatus does away with the absorption, and at the same time 
retains liquid air for a considerable number of hours, when the whole of the 
upper part is covered with a sheet of asbestos. 
* The lead box containing the apparatus is Hned with wood and asbestos, and is 
well ventilated behind the oven. Asbestos sheets screen the films from heat radia- 
tions. 
