394 Messrs. K. Honda and S. Shimizu on the Chaiuje oj 



thick which was stretched by a weight dipping in a vessel of 

 water. 



Heating was effected bj means ot* an electric current. 

 The heating coil was wound on a copper tube 40 cms. long 

 and 2'5 cms. in diameter well insulated with asbestos-paper. 

 The coil was wound anti-inductively two turns per centimetre 

 bj a wire about 1 mm. thick. Two heating coils of the same 

 dimensions were prepared, the one wound with a german- 

 silver and the other with a nickel wire. The former coil 

 w^as used in the experiments below 700° C, and the latter 

 for higher temperatures. The melting-point of nickel is about 

 1500° C, while its magnetic property is lost at a temperature 

 below 400° C. ; hence above this temperature the presence of 

 the metal does not at all disturb the magnetic field. Thus 

 by using a nickel wire for ex})eriments at high temperatures 

 we may dispense with a costly platinum wire or foil. 



The heating coil w^as fixed by means of screws to the 

 upper copper rod, while in its lower end was a hole through 

 which the lower copper rod passed without being in contact. 

 The air current which might enter or escape through this 

 narrow opening was diminished on one side by another par- 

 tition placed 3 cms. above the lower end of the coil, and on 

 the other side by a bundle of fibrous asbestos attached to the 

 copper rod just below the same end. 



The exposed parts of the copper rods and wire were well 

 covered w^itli asbestos-paper, except the part where the wire 

 came in contact with the rotating cylinder. This precaution 

 was necessary to diminish the loss of heat, and also to avoid 

 the oscillatory displacement of the image in the field of the 

 telescope due to thermal expansion and contraction caused 

 bv the air current. 



The temperature of the samples to be tested was measured 

 by means of a platinum platinum.-rhodium junction which 

 was loosely placed in contact with the sample in its middle 

 part, while the rest was insulated with asbestos-paper. The 

 other junction well insulated was inserted into a copper tube 

 dipped in a water bath of the temperature of the room. The 

 thermoelectric current in the circuit was measured by a 

 d^Arsonval galvanometer, and the constant of the pyrometer 

 was determined by means of a mercury-thermometer below 

 300° C.and by the melting-point of zinc and sodium chloride 

 above that temperature. 



A magnetizing-coil with a waterjacketed arrangement was 

 placed coaxially with the suspended rod ; it was 40 cms. 

 long and gave a field of 39*44 c.G.s. units at the centre due 

 to a current of one ampere. When adjustments were finished 



