XV 



itself, it is true, in a state of instability, and passes, without change 

 of pressure or temperature, but with evolution of heat, to a condition 

 which, by the continuous process, can only be reached by a long and 

 circuitous route." 



Like most great discoveries, this had been to a certain extent fore- 

 shadowed. In 1822 Cagniard de la Tour observed that certain liquids 

 — ether, alcohol, water — when heated in hermetically closed tubes, 

 were apparently totally changed into vapour occupying from two to 

 four times the original volume of the liquid. In 1823 Faraday 

 succeeded in condensing to liquids a number of substances previously 

 known in the gaseous state only. 



Shortly afterwards Thilorier obtained solid carbonic acid, and 

 observed the very rapid expansion of liquid carbonic acid when heated. 

 In 1845 Faraday published a very remarkable paper in the ' Philoso- 

 phical Transactions ' on the liquefaction and solidification of gases. 

 He there pointed out that as different liquids assume the Cagniard de 

 la Tour state at different temperatures, so the gases which had not 

 been condensed — oxygen, hydrogen, nitrogen, &c. — might be supposed 

 to have that point below the lowest temperature he had applied (that 

 of a bath of solid carbonic acid and ether in vacuo), and therefore to 

 be incapable of condensation to a liquid by any pressure unless the 

 temperature were much further lowered. 



Faraday conjectured from the results of experiment that the 

 Cagniard de la Tour state occurred, in the case of carbonic acid about 

 90° F. r a value surprisingly near that experimentally proved by 

 Andrews. 



But what others had seen obscurely or partially, or had inferred, 

 Andrews made clearly visible in its entirety, and many physicists and 

 chemists can testify to the startling character of the revelation made 

 by the publication of his discovery. It is in fact after the discovery 

 has really been made that the historian begins to look for foreshadow- 

 ings, and we are perhaps somewhat inclined to interpret these early 

 indications in the light of the later, more definite knowledge, but the 

 unanimous verdict of the scientific world is that the discovery of the 

 continuity of the liqmid and gaseous states belongs to Andrews and to 

 him alone. 



Dr. Andrews was loved by all who knew him. Warmly hospitable, 

 he was personally almost stoically temperate, allowing himself the 

 minimum of rest, of food, and of sleep. While in theological, as in 

 all other matters, he thought for himself, he was a consistent and 

 orthodox Christian and a loyal member of the Church of Ireland. 



A. C. B. 



