2 2 Mr. J. Brown on 



and one only, would be recalled by the word " Belfast." It 

 would not be a name connected with our boasted manufactures, 

 our great political lights, or our popular celebrities of any kind. 

 It would be the name of Thomas Andrews, the fame of whose 

 work on the continuity of the liquid and gaseous states is of 

 course world-wide. 



Before Andrews's time, we find that in 1823 Faraday had 

 succeeded in liquefying chlorine, sulphuric acid, and some 

 other gases. Faraday, however, did not succeed in liquefying 

 oxygen, hydrogen, nitrogen, &c. 



In 1861 Andrews subjected these intractable gases to very 

 great pressure, also without success, but on more easily con- 

 densible gases his subsequent work had a value far exceeding 

 this in scientific interest. 



In order to fix our ideas as to the conditions necessary for 

 the liquefaction of gases let me point as an illustration to the 

 homely matter of water boiling under ordinary conditions. 

 Evidently heat is required. It is the tendency of heat to 

 produce vapour or gas from liquid. Conversely we may 

 conclude it is a tendency of cooling to produce liquid from a 

 gas or vapour like steam. Here, however, is only half the 

 matter. When water boils in ordinary conditions it is under 

 the atmospheric pressure of 151b. per square inch on its surface, 

 and the vapour rising from it has to lift this 151b. off before it 

 can form. As a matter of experiment we know that it will not 

 lift this pressure till the temperature is raised to 100 degrees C. 

 It would be natural to expect, however, that if we lift this 

 atmospheric pressure off by other means a less temperature 

 would suffice for converting the liquid into gas. We shall 

 therefore not be very much surprised to see water boiling and 

 freezing at the same time. Having exhausted the air from 

 above the water in a glass vessel, you see it boiling violently, 

 although quite cold enough to form ice. which is presently seen 

 on its surface. 



From this experiment we draw the conclusion that the 

 essening of pressure tends to form gas from liquid, and 



