284 



Messrs. C. G-. Lamb and W. G-. Wilson. 



motor with a fan attached to the axis ; a tin-plate cylinder, open at the 

 top and with holes at the bottom, was put inside to direct the currents 

 of air over the inner surface of the inside pot, in the direction of the 

 arrows shown in Fig. 1. Energy was supplied electrically to a heating 



Tig. 1. 



coil within as well as to the motor : this constituted an internal supply 

 of heat, which maintained the temperature within the pot at any 

 decided upper limi^. The motor and heating coil were connected in 

 series, and leads were carried through a small hole in the lid of the 

 pots to measure the current and potential difference, and thus the 



