y 



1912] on Very High Temperatures. 



317 



the great objects of science, and that this batteiy 

 be erected in the laboratory of the Royal 

 Institution." The sum required, -a little over 

 £500, was soon got together, and at the con- 

 cluding lecture of the 1812 season the battery 

 was put in action for the first time. We read 

 in Davy's " Elements of Chemical Philosophy," 

 iv. p. 110, an account of how he applied the 

 battery to the running of an electric " arch " 

 between two carbon rods. Parts of Davy's 

 battery are still preserved at the Royal Institu- 

 tion. 



I begin my lecture thus, merely to emphasize 

 once more the truth of the adage of 3000 years 

 ago : " There is no new thing under the sun." 



In 1912, when considering the subject of 

 " very high temperatures," we can claim, com- 

 paratively speaking, to be capable of little more 

 than Davy accomplished a century ago. In his 

 arc he melted all the most infusible materials 

 known to him, including lime and maguesia, 

 which are among the most refractory materials 

 in use at the present day. 



Turning now from the historic to the present 

 aspect of our subject, permit me to begin with 

 a few elementary considerations as to our con- 

 ception of temperature. I think I am correct 

 in saying that everyone has some idea in his 

 own mind of a temperature-scale, a kind of 

 intuition which is generally a fairly useful one 

 for practical purposes. Probably I am not 

 exaggerating when I say that even men of 

 science, who always think for their professional 

 purposes of temperatures on the Centigrade 

 scale, find themselves obliged to convert to 

 Fahrenheit for an idea of the temperature of a 

 room or of a summer's day. 



I have endeavoured to give a graphic repre- 

 sentation (Fig. 1) of the temperature scale as 

 we know it, both in Centigrade and Fahrenheit 

 degrees. You will notice the smallness of the 

 int'erval between the extreme temperatures that 

 prevail in the arctics and the tropics ; and how 

 restricted the " eold " region down to absolute 

 zero is compared with the possibilities in the 

 other direction. While, on the one hand, 

 Kammerlingh tines by the evaporation of 



