190 TRANSACTIONS OF THE [MARCH 15, 



pro foil lul studies of the relations between chemical constitution 

 and the phenomena of diffusion, of capillarity, of dialysis, of 

 dissociation, and of the law of isomorphism. We read investiga- 

 tions on the value of the theory of atomicity, and on the nature 

 of nascent action. Researches in the domain of electro-chemis- 

 try, especially in connection with the various forms of storage 

 batteries, and in relation to the methods and results of electrol- 

 ysis, are of such importance as to merit a whole address. The. 

 press also records numerous studies in actinometry, of the rela- 

 tions between chemical composition and fluorescence and phos- 

 phorescence, as well as of polychroism, and of the results of 

 spectrum observations. Noteworthy are the special apjilicatious 

 of optical methods to the detei'mination of molecuhii- structure, 

 viz., the relations between chemical composition and (1) the 

 refractive power; (2), the power of rotating a ray of polarized 

 light; and (3), the absorption spectra of both inorganic and or- 

 ganic bodies. 



Bruhl has attempted to show that the relationship between re- 

 fractive power and molecular structure is dependent on the valen- 

 cies of atoms, and on the distribution of atomic interactions. 

 Van 't Hoflf has developed a hypothesis of a crystallographic 

 character that cannot be discussed in the brief space at our com- 

 mand." 



(14.) The meeting of the French Academy of Sciences, held 

 the day before Christmas, 1877, was rendered memorable by the 

 announcement that oxygen gas had been liquefied by two indepen- 

 dent experimenters. Previous to that date, hydrogen, oxygen, 

 nitrogen, nitric oxide, marsh gas, and carbon-monoxide had re- 

 sisted all attempts to liquefy them, whetlier in the hands of the 

 skilful Faraday, the ingenious Natterer, or the learned Andrews. 

 Physicists and chemists, while admitting the class of so-called 

 permanent gases, had for many years looked forward to their 

 eventual liquefaction, yet the final success came as a surprise. 

 This success was the result of the enterprise and ingenuity of a 

 French iron-master, M. Cailletet, and of a Genevan manufacturer 

 of ice-machines, Raoul Pictet, working independently. In each 

 case, the process consisted in simultaneously exposing the gases 

 to a very high pressuie and a very low temperature. Pictet'^ 

 obtained the necessary pressure by generating the oxygen in a 

 wrought-iron vessel strong enough to withstand an enormous 

 strain, and the low temperature was secured by tlie rapid evapo- 

 ration of liquid carbonic acid; Cailletet,'" whose apparatus was 

 marked by extreme simplicity, obtained the great pressure by 

 means of a hydraulic press, and the low temperature by suddenly 

 diminishing the i)ressure upon the compressed gases. Descrip- 

 tions of apparatus without diagrams are seldom intelligible; in 



