556 



Mr. Richard fhrelfall 



[March 19, 



plug. This is then bored out with a hard steel drill to the required 

 diameter. In pressing magnesia I have found that it is not possible to 

 thoroughly consolidate the powder in greater thickness than a few 

 millimetres, even under a pressure of 50 tons per square inch. In 

 fact magnesia is a substance which appears to be almost devoid of 

 the fluid properties so marked in graphite — an essential condition for 

 its use in the apparatus. I have tried various other linings, ground 

 flint, alumina, etc., but they have no advantage over magnesia, and 

 are even more difficult to drill out. Alumina prepared from the 

 crystalline hydroxide is very easily compressed into cakes, and makes 

 a good lining, but it is too fusible for experiments on carbon, and is 



sSl 



ffi 



EZZ 



E=n 



:© 



D 



TO" 



^ur 



Fig. 8. 



probably more easily reduced. The cylinder having been lined, the 

 bottom is filled in with Acheson graphite in electrical communication 

 with the base of the apparatus. The substance to be operated upon 

 is placed in the narrow part of the bore, and packed in with graphite 

 or lead if that is suitable. The pressure is applied by a ram of 

 hardened high speed steel, working upon a reservoir of graphite or 

 lead contained in the plug closing the cylinder at the top and electri- 

 cally connected to the other terminal of the supply. The chief 

 uncertainty in regard to the pressure which actually reaches the 

 subject of the experiment Hes in the possibility of the ram being 



