08<> Mr. S. C. Laws on the Change of Resistance of Metals 



to adjust the balance accurately. The ratio arms of manganin 

 were 51 and 5*1 ohms (or in the case o£ carbon 51 and 0'48 

 ohms) respectively. These, together with the battery series 

 resistance, were immersed in an oil-bath. 



Fisr. 1. 



The method of procedure was to first adjust Y and then X 

 until the balance was nearly obtained and then, keeping X and 

 Y constant, to observe the deflexion produced by reversing the 

 battery current through the bridge. Finally, the readings 

 were standardized by observing the deflexion due to a reversal 

 of the battery-current when a small alteration of the resistance 

 X was made. In this way, the resistance r of the experi- 

 mental wire was obtained both when the field was " off " and 

 "on." 



In the case of the metals Cadmium and Zinc, these were 

 obtained in the form of silk-covered wires *003 inch 

 diameter, and a piece about one yard in length was wound 

 lightly round a small rectangular mica frame so that the coil 

 would lie easily in the space between the poles of an electro- 

 magnet. Conducting leads were fastened to a strip of 

 vulcanized fibre and the ends of the experimental wire 

 attached with soft solder to these. 



Ficr. 2. 



\z 



The temperatures were obtained by surrounding the coil 

 with a rectangular bath, a section through the centre of which 

 is here represented, with recesses in opposite faces to bring 

 the pole-pieces of the electromagnet as nearly as possible to 

 the coil. 



The pole-pieces were maintained at a constant distance 



