424 



Sir James Dewar 



[Jan. 28, 



showing a continuous displacement of 1 cm. or more per minute 

 with the shutter closed. Thin German silver may be used instead of 

 ebonite, but there is then more conduction into the flask, and con- 

 sequently slight condensation of ice on E and M within the rim of 

 the flask when left for long periods. 



Fig. 7. 



In Figs. 6 and 8, H is a light hollow copper cylinder with three 

 equal and symmetrical diaphragms (one at each end and one in the 

 centre), whose apertures are all 2h cm., equal to that of the cell. 

 H is shown in Fig. 6 attached to the cell to give the relative position 

 of the parts, but in use it is fitted into the neck of A after B has 

 been adjusted (as in Fig. 8) ; a moderately springy sliding fit affords 



