I-J" 



DR. K. II GRIFFITHS AND MR. EZER GRIFFITHS ON THE 



In the same manner when in ice : 



Difference when determined separately 

 Difference when determined differentially 



+ 0'028. 

 + 0'027. 



In the course of such a comparison, eight connections had to be undone, re-made 

 separately in sets of four, and then replaced in the first position .i.e., 12 removals ;m<l 

 replacements. In the one case, a large number of the box coils were in use ; in the 

 other, the bridge wire only. The identity of the results is sufficient proof of the 

 accuracy of the methods employed. These thermometer coils were surrounded by 

 very thin walled tubes of Jena glass which fitted closely into the holes in their 

 rwpective blocks and thermal connection between these tubes and the surrounding 

 walls was assisted by a thin film of oil of known weight. 



Although the observations with AB and CD appeared satisfactory, it was decided, 

 after a considerable number of determinations of specific heats had been made by 

 their means, to alter the conditions and replace them by two other thermometers 

 labelled AA and BB. In these, the platinum leads were fused through glass heads, 

 while the protecting tube was cut off just above the top of the coils, leaving about 

 ij cm. to 2 cm. of glass projecting into the hole in the metal block.* 



These thermometers were standardised by temporarily surrounding them with thin 

 tubes containing sufficient oil to completely cover their coils, as we proposed to 

 immerse them similarly when in the blocks. We afterwards found, however, that 

 the effect of the oil was to increase, rather than decrease, the temperature " lag." 

 Their coils were therefore freed from any traces of oil by washing with ether. 



Their temperature then very rapidly responded to changes of temperature in the 

 walls of their cavities, their heat capacity being very small as compared with their 

 The constants of AA and BB were as follows : 



areas. 



After a considerable number of experiments had been performed, the glass head of 

 AA was fractured. It was replaced by another thermometer of the same type which 

 had been in our possession for the last 13 years. 



Its resistance, however, was slightly less than that of BB. It was necessary, 

 therefore, to reduce the latter until the two became approximately equal. These 

 thermometers were labelled AA' and BB'. Their constants were : 



' The tube* being wrapped round with threads of asbestos to prevent the passage of convection currents 

 from the canty. 



