666 



Mr, Richard T. Glazebrook 



[May 24, 



Table III. — Values of Corrections to the English Glass Thermometer 

 Scale to give Temperatures on the Gas Thermometer Scale found 

 by various Observers. 



It is clearly important to establish in England a mercury-scale of 

 temperatures which shall be comparable with the hydrogen scale, and 

 it is desirable to determine as nearly as may be the relation between 

 this and the existing Kew scale. 



I am glad to say that in the first endeavour we have secured the 

 valuable co-operation of Mr. Powell, of the Whitefriars Works, and 

 that the first specimens of glass he has submitted to us bid fair to 

 compare well with 16"'. 



Another branch of thermometry in which there is much to do is 

 the measurement of high temperature. Professor Callehdar has 

 explained here the principles of the resistance thermometer, due first 

 to Sir W. Siemens. Sir W. C. Roberts-Austen has shown how the 

 thermopile of Le Chatellier may be used for the measurement of high 

 temperatures. There is a great work left for the man who can 

 introduce these or similar instruments to the manufactory and the 

 forge, or who can improve them in such a manner as to reuder their 

 uses more simple and more sure. Besides, at temperatures much 

 over 1000° C, the glaze on the porcelain tube of the pyrometer gives 

 way. 



So far we have discussed new work, but there is much to be done 

 in extending a class of work which has gone on quietly and without 

 much show for many years at the Kew Observatory. Thermometers 

 and barometers, wind gauges and other meteorological apparatus, 

 watches and chronometers, and many other instruments are tested 

 there in great numbers, and the value of the work is undoubted. 

 The competition among the best makers for the first place, the best 

 watch of the year, is most striking and affords ample testimony to the 

 importance of the work. 



Work of this class we propose to extend. Thus, there is no place 

 where pressure gauges or steam indicators can be tested. It is 



