Manchester Memoirs, Vol. xliii. (1899), No. 4. 



THE WILDE LECTURE. 



IV. The newly discovered Elements; and their Relation 

 to the Kinetic Theory of Gases. 



By Professor WILLIAM RAMSAY, F.R.S. 



(Delivered March 28th, i8gg.) 



When a body of any kind, be it solid, liquid, or 

 gaseous, is in a condition in which it can be made to do 

 work, it is said to possess available energy, A coiled 

 spring, a reservoir of v/ater on a hill, a compressed gas ; 

 these are all instances of bodies in possession of available 

 energy, for from all of them work may be obtained ; from 

 the spring, by allowing it to uncoil, and drive such a 

 mechanism as a watch ; from a reservoir of water, by 

 opening the sluice, and utilising the descent of the water 

 under the attraction of the earth to cause a mill-wheel to 

 revolve ; from a compressed gas, by allowing it to expand 

 into the cylinder of an engine, and raise a piston. Heat, 

 too, is a form of energy ; and its numerical relation to 

 mechanical and to gravitational energy, discovered by 

 your fellow-townsman, Joule, will ever remain connected 

 with his name, and with the city where his discovery was 

 made — jnonuinentum aere perennhis. 



By heating a body, therefore, energy can be com- 

 municated to it ; it then becomes capable, if placed in 

 appropriate environment, of performing work. The work 

 done by a steam engine is owing partly to the expansion 

 of the compressed steam, partly to its loss of heat in 

 expanding. Every body has its own power of holding 

 heat ; a pound of water has much greater capacity for 

 heat than a pound of mercury ; that is, it is cap ableof 

 holding more heat. If the capacities of holding heat are 



May 17th, i8gg. 



