27 



were driven by an eleetromotor at a speed of 200 révolu- 

 tions per minute. 



Fig. 3. Scale 1 : 5. 

 Dimensions 40 X 40 cm. 



The outer vessel had a width of 40 cm., a height of 

 40 cm. and a depth of 60 cm. The dimensions of the 

 inner vessel were 30 X 30 X 50 cm. 



In the second* place heating by gas was excluded and 



