Dec. 17, 1885] 



NA TURE 



159 



The whole subject was in that chaotic state which 

 naturally precedes the advent of the Kepler who is to 

 marshal, under a few general statements, each intrinsically 

 simple, the mass of apparently irreconcilable phenomena. 



Andrews' classical researches completely effected this 

 simplification. Guided by the results of Regnault, he 

 selected carbonic acid as the substance whose behaviour 

 was made the subject of exhaustive study through wide 

 ranges of temperature and of pressure. He devised an 

 extremely ingenious form of apparatus for the purpose, 

 had the coarser metallic parts constructed under his own 

 eye by a remarkably skilful mechanic ; and himself made 

 and calibrated the glass portions, purified with great care 

 and skill the gas to be operated on, and finally fitted up 

 the whole with unwearying patience. 



The simpler and more prominent results of this splendid 

 research may be briefly summed up as follows : — 



(a) When carbonic acid is maintained at any tempera- 

 ture whatever above 30°'9 C, it cannot even in part be 

 condensed into liquid by any pressure however great. 



ip) If the temperature be below jO^'g C-, the gradual 

 increase of pressure ultimately leads to liquefaction ; but 

 the pressure of the vapour in presence of the liquid is less 

 as the temperature is lower. 



(f) A cycle of operations, in Carnot's sense, can be 

 performed on liquid carbonic acid in such a way that, 

 during the first stage of the expansion we have optical 

 proof of the existence of liquid and gas side by side in 

 the same vessel ; while on compressing again at a higher 

 temperature, and finally cooling down to the original 

 temperature and volume, the whole contents are once 

 more liquid ; though at no stage of the latter part of the 

 operation is there any appearance of the joint presence 

 of two different states of matter. It is this fact which 

 suggested the title of the paper. 



((/) The key to the explanation of observed deviations 

 from Boyle's Law was furnished by his study of the iso- 

 thermals of carbonic acid at temperatures not much above 

 30° '9 C. For Andrews's measurements show that the 

 product of pressure and volume (which, by Boyle's Law, 

 should be constant) diminishes with volume to a mini- 

 mum, and thereafter rises rapidly as the volume is farther 

 diminished. 



Many other valuable results, such as the great com- 

 pressibility of liquid carbonic acid, especially at tempera- 

 tures near to 30'^ C. ; the alteration of surface-tension of 

 the liquid, and of its angle of contact with glass, as the 

 temperature is raised, &c., appear as mere side-issues of 

 this investigation. 



The discovery of this Critical Temperature, or Critical 

 Point, soon led to the liquefaction (and in certain cases 

 even to the solidification) of the gases which had been 

 called "non-condensable." Andrews' work had supplied 

 all the necessary hints for the adaptation of his apparatus 

 to such a purpose. In fact the main requisites were (i) 

 to work on a larger scale, (2) to employ very low tem- 

 peratures, and especially (3) to provide a means of 

 ensuring sudden relaxation of pressure. The work of 

 Pictet, Cailletet, v. Wroblewski, Amagat, &c , on this 

 subject, followed as a natural and immediate consequence 

 of that of Andrews. 



The writers have, like many others, seen and admired 

 the confident manipulation, by Andrews, of wide sealed 

 tubes, half full of liquid carbonic acid ; how he, knowing 

 the soundness of his own glass-blowing, boldly heated 

 such tubes in the flame of a Bunsen lamp, till the liquid 

 entirely disappeared, and pointed out with eager enjoy- 

 ment the extraordinary phenomena presented as the 

 contents cooled nearly to the critical temperature. The 

 whole tube seemed, for a short time, to be filled with a 

 substance presenting, to an exaggerated degree, the 

 appearance of a mixture of water and alcohol before 

 diffusion has sensibly operated. 



We have spoken of Andrews's remarkable skill in 



manipulation, and of his unwearied patience. But even 

 these were eclipsed by the perfect calmness with which, 

 though on the very verge of an important discovery, he 

 attended to every point of minute and laborious detail ; 

 so that his first successful experiment was as exactly 

 carried out and recorded as was its future repetition. 

 This was all the more remarkable in that he was usually, 

 especially in public, a man of a highly nervous and 

 excitable temperament. 



An excellent French and German scholar, he kept 

 himself always well acquainted with the most recent pro- 

 gress of science, whether chemical or physical. He con- 

 structed his own dividing-engine for the calibration of the 

 exquisite thermometers which he made for his researches 

 on heat ; and his air-pump (in which he took special 

 delight) was furnished with numerous valuable improve- 

 ments all devised by him for particular applications. His 

 laboratory books were models of ample, but not super- 

 fluous, detail. 



He was, personally, a man of simple unpretending 

 manner ; conscientious almost to an extreme, but tho- 

 roughly trustworthy and warm-hearted ; an excellent 

 example of the true Christian philosopher. 



NOTES 



We regret to announce the death of Mr. Alfred Tribe, the 

 well-known chemist, on November 26, at the age of forty-six 

 years. We defer to next number a notice of Mr. Tribe's 

 career. 



A MEETING of the subscribers to the testimonial to Dr. H. 

 Woodward, F.R.S., for twenty-one years editor of the Geologi- 

 cal Magazine, was held on the 15th inst., at the rooms of the 

 Geological Society, Burlington House, when Prof. T, G. Bonney 

 (Pres. Geol. Soc. ) presented to that gentleman, on behalf of the 

 subscribers, a silver tea and coffee service and a cheque for 253/. 

 On making the presentation, Prof. Bonney addressed Dr. Wood- 

 ward, referring to the invaluable services he had rendered to 

 science during the twenty-one years he has had charge of the 

 Geological Magazine. In replying, Dr. Woodward referred 

 briefly to the career of the Magazine and its predecessors, to 

 the many distinguished men that had been connected with them, 

 and to the period of remarkable scientific interest thus covered. 

 Over 200 names are on the list of subscribers to the testimonial. 



The loth instant was a red-letter day at the French Institute. 

 M. Bertrand was introduced as member of the Academie 

 Fran9aise, and read an address which, according to custom, was 

 devoted entirely to thanl^ing his brother Academicians and to 

 eulogising his immediate predecessor, M. Dumas. The address 

 was acknowledged by another oration from M. Pasteur, who 

 after having summarised the life of M. Bertrand, gave a long 

 and interesting account of the career of M. Dumas. Great 

 enthusiasm prevailed throughout the proceedings, and the hall 

 was crowded. 



The number of patients in the special clinic of M. Pasteur 

 is increasing daily, several arriving from foreign countries. No 

 less than forty were inoculated on December 14 before the 

 Minister of Agriculture, who acknowledged the services rendered 

 by Pasteur to humanity. Among the patients is an officer of 

 the Czar's body-guard, just arrived from St. Petersburg. 



A BIOGKAPHV of the late Sir William Siemens is being pre- 

 pared, at the desire of the executors, by Dr. AVilliam Pole, 

 F.R. S., Hon. Secretary of the Institution of Civil Engineers, 

 and author of the " Life of Sir William Fairbairn, Bart." Dr. 

 Pole will be grateful for the loan of any of Sir William's letters, 

 or for any information of importance. Address, Athenaeum 

 Club, S.W. 



On Saturday, last week, the rainfall at the Ben Nevis Ob- 

 servatory amounted to 4'99I inches, and on the Sunday following 



