648 Tra7isactions of the Boyal Society of South A frica. 
ou the determination of the energy of an atom at zero temperature, the 
following pieces of apparatus are described. 
Construction or Heating Oven. 
Two cones of copper are cast from models in which the vertical angle of 
the cone is a right angle. 
These cones are then cut down so as to fit over a copper cylinder. (See 
Fig. 1.) 
One cone is permanently screwed on the cylinder ; the other has a cap on 
it so that it just slips over the cylinder. 
The movable cone is then drilled so that four screws may clamp the 
crystal at its vertex. 
These screws are sunk in the holder so that the crystal-carrying cone may 
be moved flush against the fixed cone. 
The cylinder is lined with asbestos packing both inside and outside. 
Two rings are now cut out of a fairly thick piece of mica (Fig. 2). 
Small holes are drilled through each of these rings so that the threads 
of the steel rods (Fig. 3) may pass through them. 
