526 Mr Wade, Method of facilitating the measurement [May 1(5, 



(2) On a Metltod of facilitating the measurement of tem- 

 perature by means of Platinum Thermometry. By E. B. H. 

 Wade, B.A., Trinity College. 



§ 1. Object of the Paper. 



The method of measuring temperatures by finding the 

 resistance of a platinum wire, claims a high degree of accuracy 

 and is also widely applicable. Probably one reason why it is not 

 more frequently used, is that equal increments of resistance do not 

 represent equal increments of temperature, so that inconvenient 

 calculations are required to deduce the latter. The object of this 

 paper is to describe a means of avoiding these calculations. It is 

 assumed that the formula employed by Callendar and Griffiths is 

 exact, and if the directions contained in the paper are followed 

 every unit of resistance will represent the same interval of tem- 

 perature, which may be 1° Centigrade or any other. It is hoped 

 that this will lead to the adoption of platinum thermometry by 

 those who have hitherto been deterred by the calculations. 



§ 2. Description of a modification of Wheatstone's Bridge, 

 which gives direct readings with platinum thermometers. 



Fig. 1 represents a form of Wheatstone's Bridge in which P is 

 a platinum thermometer having resistance R t at temp. t. 



A, B, are coils of equal resistance of a galvanometer. If a 

 single adjustable resistance were situated between points 0, D, 





the whole arrangement would be that in ordinary use. But 

 in the suggested modification this interval is occupied by two 

 adjustable resistances in parallel forming a shunt. And these 

 coils are to be manipulated according to the following rule. 



