1894.] President's Address. 49 



supply and sewage, and illuminating gas, Las proved of great practi- 

 cal value, and has rendered his name famous in connection with the 

 application of chemistry to technical purposes. 



RUMFORD MEDAL. 

 Professor Dewar. 



During more than twenty years past Professor Dewar has been 

 engaged in researches of great difficulty, in the first instance at very 

 high, and latterly at very low temperatures, his inquiries having 

 extended over an extraordinarily wide field, as will be seen by refer- 

 ence to the ' R.S. Catalogue ' of scientific papers. 



In conjunction with Professor Liveing, he has communicated to 

 the Royal Society a large number of papers which have added much 

 to our knowledge of spectroscopic phenomena. 



During recent years he has made the liquefaction of gases a 

 subject of deepest study, and in the course of this work has dis- 

 played not only marvellous manipulative skill and fertility of 

 resource, but also great personal courage, such researches being 

 attended with considerable danger. One of his chief objects has 

 been so to improve and develope the methods of liquefying the more 

 permanent gases that it shall become possible to deal with large 

 quantities of liquid, and to use such liquids as instruments of 

 research in extending our knowledge of the general behaviour of sub- 

 stances at very low temperatures. In this he has already been highly 

 successful . Not only has he succeeded in preparing large quantities 

 of liquid oxygen, but he has been able by the device of vacuum- 

 jacketed vessels to store this liquid under atmospheric pressure 

 during long periods, and thus to use it as a cooling agent. Very 

 valuable outcome of these labours has been the series of determina- 

 tions, made by him in con junction with Dr. Fleming, of the electrical 

 conductivity of metals at exceedingly low temperatures, which have 

 furnished results of a most unexpected character, and of extraordi- 

 nary interest and importance. Professor Dewar's experiment show- 

 ing the great magnetic susceptibility of liquid oxygen is exceedingly 

 important and interesting. His recent observations on phospho- 

 rescence, and on photography,* and on ozonef at very low tempera- 

 tures, have given surprising results of a highly instructive and in- 

 teresting character. It is difficult to exaggerate the importance of 

 extending these researches, which certainly deserve all possible 

 encouragement and support. The award of the Rumford Medal to 

 Professor Dewar is made in recognition of the services which he 

 has rendered to science by the work which he has already done and 



* ' Chem. Soc. Proc.,' June 28, 1894. 

 f ' Phil. Mag.,' August, 1894, pp. 238, 239. 

 VOL. LV1I. E 



