124 Henry Riddell on 



the liquefaction of any gas was only a question of sufficient 

 pressure and sufficient cold, and that there existed for each gas 

 a temperature above which pressure alone, no matter how great, 

 Avould not produce liquefaction. Faraday was one of the most 

 intimate friends Andrews possessed. He was the son of a black- 

 smith and was both a scholar and a gentleman, though there 

 is rather a malicious story as to Lady Davy and him. He 

 accompanied Davy to Paris as his assistant, and in an emergency 

 undertook to act as his valet. The French scientists were not 

 long in discovering the nature of the young man they met, and 

 placed him at dinner with Sir Humphry and his wife. It is said 

 that Lady Davy was highly indignant that a servant should have 

 such a position, and other arrangements had to be made for the 

 rest of the visit. 



It Avas about 1860 that Dr. Andrews began the experiments, 

 which first took the form of an inquiry into the effect on various 

 gases of combined pressure and cold. In this inquiry he used 

 pressures as great as 500 atmospheres and a degree of cold 

 approaching - 110°C. Later on he devoted himself to an investi- 

 gation of Carbon Dioxide, Carbonic Acid as it was then always 

 called, with the view of discovering some law which might be 

 connected with liquefaction generally, and in this he was 

 eminently successful. 



The apparatus used is shown in the engraving, fig. I. It con- 

 sists essentially of two metallic tubes, to the upper flanges of which 

 glass tubes can be connected. The two metallic tubes are in full 

 communication at the bottom and are filled with water, so that 

 the pressure in both will be alike, whatever its value. The tubes 

 are of cold drawn copper, and the general arrangement is easily 

 understood from the drawing. In my day at Queen's, Andrews 

 was engaged in repeating and varying the experiments described 

 in his Bakerian lecture of 1876, and at this time had improved 

 the apparatus, Ijy somewhat increasing the diameter of the metal 

 tubes, and inserting the lower ends of the glass tubes into small 

 glass reservoirs of mercury resting on ledges within the metallic 



