560 Professor Dewar [Jan. 22, 



induction coil or transformer, with a closed air-core circuit, but which, 

 when immersed in a liquid, by the penetration of the liquid into the 

 interior of the primary coil, became changed into a closed circuit 

 transformer, with a liquid core. The transformer so designed was 

 capable of being placed underneath liquid oxygen contained in a 

 largo vacuum vessel, and when so placed formed a transformer of the 

 closed circuit type, with a core of liquid oxygen. The coefficient of 

 mutual induction of these two circuits, primary and secondary, is 



Fig. 1. — Diagram of the Closed Circuit Transformer used in Experiments. 



therefore altered by immersing the transformer in liquid oxygen, 

 but the whole of the induction produced in the interior of the 

 primary coil is always linked with the whole of the turns of the 

 secondary coil, and the only form-change that can be made is a small 

 change in the mean perimeter of the primary turns due to the con- 

 traction of the coil as a whole. In experiments with this transformer 

 the transformer was always lifted out of the liquid oxygen into the 

 cold gaseous oxygen lying on the surface of the liquid oxygen, and 



