Dr. C. Chree. Im-ixt /.//>//.*, /.s- ,,/t 



kindly vMted the Observatory, and illustrated the methods of 

 'In- apparatus. 



An account of the original installation was given by Mr. (iriffiths in 

 ' Nature,' Nov. 14, 1895, pp. 39-46. As this paper and several more 

 recent papers by Professor Callendar and others have discussed the 

 fundamental facts of platinum thermometry very fully, I have judged 

 it unnecessary to go into such details here. 



Thermometers. 



2. The six original thermometers, distinguished as KI to K, were 

 all made from one sample of platinum wire. In 1896 a seventh 

 thermometer, K-, was obtained from the Instrument Company. It is 

 believed to be of the same sample of platinum wire as the others, but 

 this is not absolutely certain. Particulars as to the type of the 

 thermometers are given in the following table : 



Table I. 



The resistance at C. of K is about 6-5 ohms, while the resistance 

 of each of the other thermometers at C. is about 2'6 ohms. 



Since it came to Kew, K has been exposed to no temperature above 

 the steam point; whilst K 3 , K 4 , K 5 , and K 7 have not been taken above 

 the sulphur point (444'53 C. according to Callendar and Griffiths, 

 under normal pressure). In their early days, KI and Iv were heated 

 on several occasions to the temperature of melting silver (approx. 

 960 C.). 



After a few months' use, Kj began to behave unsatisfactorily. The 

 Instrument Company reported after inspection that the tube was 

 slightly short, and a new tule was fitted in March, 1896. The career 

 of K-J has l>een chequered. The first tul>e broke in melting silver in 



