October 10, 1902.] 



SCIENCE. 



567 



ell 's style is terse to a fault. Usually he is 

 satisfied with the simplest statement of 

 his conclusions. Sometimes he adds illus- 

 trations. Only rarely does he explain them 

 by setting forth their premises. It has thus 

 happened that some of his earlier work, 

 though eventually recognized as of high 

 importance, was at first either not appre- 

 ciated or misunderstood. The value of his 

 anthropologic philosophy, though now 

 widely appreciated, was recognized but 

 slowly outside the sphere of his personal 

 influence. His philosophic writings belong 

 to a field in which thought has ever found 

 language inadequate, and are for the pres- 

 ent, so far as may be judged from the re- 

 views of 'Truth and Error,' largely mis- 

 understood. Admitting myself to be of 

 those who fail to understand much of his 

 philosophy, I do not therefore condemn it 

 as worthless, for in other fields of his 

 thought events have proved that he was not 

 visionary but merely in advance of his 

 time. 



To the nation he is known as an intrepid 

 explorer, to a wide public as a conspicuous 

 and cogent advocate of reform in the laws 

 affecting the development of the arid West, 

 to geologists as a pioneer in a new province 

 of interpretation and the chief organizer 

 of a great engine of research, to anthro- 

 pologists as a leader in philosophic thought 

 and the founder, in America, of the new 

 regime. 



G. K. Gilbert. 



THE ADDRESS OF THE PRESIDENT OF THE 

 BRITISH ASSOCIATION FOR THE AD- 

 VANCEMENT OF SCIENCE. 



II. 



LIQUEFACTION OF GASES AND CONTINUITY 

 OF STATE. 



In these speculations, however, chemists 

 were dealing theoretically with tempera- 

 tures to which they could not make any but 

 the most distant experimental approach. 



CuUen, the teacher of Black, had indeed 

 shown how to lower temperature by the 

 evaporation of volatile bodies such as 

 ether, by the aid of the air-pump, and the 

 later experiments of Leslie and Wollaston 

 extended the same principle. Davy and 

 Faraday made the most of the means at 

 command in liquefying the more condens- 

 able gases, while at the same time Davy 

 pointed out that they in turn might be 

 utilized to procure greater cold by their 

 rapid reconversion into the aeriform state. 

 Still the chemist was sorely hampered by 

 the want of some powerful and accessible 

 agent for the production of temperatures 

 much lower than had ever been attained. 

 That want was supplied by Thilorier, who 

 in 1835 produced liquid carbonic acid in 

 large quantities, and further made the 

 fortunate discovery that the liquid could be 

 frozen into a snow by its own evaporation. 

 Faraday was prompt to take advantage of 

 this new and potent agent. Under ex- 

 haustion he lowered its boiling-point from 

 minus 78° C. to minus 110° C, and by 

 combining this low temperature with pres- 

 sure all the gases were liquefied by the year 

 1844, with the exception of the three ele- 

 mentary gases — hydrogen, nitrogen, and 

 oxygen, and three compound gases — car- 

 bonic oxide, marsh gas, and nitric oxide; 

 Andrews some twenty-five years after the 

 work of Faraday attempted to induce 

 change of state in the uncondensed gases 

 by using much higher pressures than Fara- 

 day employed. Combining the tempera- 

 ture of a solid carbonic acid bath with 

 pressures of 300 atmospheres, Andrews 

 found that none of these gases exhibited 

 any appearance of liquefaction in such high 

 states of condensation ; but so far as change 

 of volume by high compression went, An- 

 drews confii-med the earlier work of Nat- 

 terer by showing that the gases become 

 proportionately less compressible with 

 growing pressure. While such investiga- 



