Notices respecting New Books, 869 



A few experiments were made to see if different physical 

 or crystallographic conditions affected the sublimation tem- 

 perature. Sphalerite was testedinthe following varieties: — 

 (1) Transparent amber and brown crystal (Santander), 

 630; (2) Pale olive-green transparent crystal (Cornwall), 

 600: (3) Small, brilliant opaque crystals (loc ?), 6i0; 

 (4) Fibrous, dark brown crystals (loc.?), 600; (5) Hepatic 

 blende (Cornwall), 600. Sphalerite shows considerable 

 variations in its specific heat according to its state of 

 aggregation. The above results, depending on the internal 

 stability of the molecule, reveal no definite variation. 



Iveagh Geological Laboratory. 



LXXXIX. Notices respecting New Books. 



Les Atomes. By Professor Jean Perejds". 

 Pp. xvi+^96. Paris : Pelix Alcan, 1913. 3 fr. 50. 



r T\EIS volume in the Nouvelle collection scientifique is essentially 

 -*- the story of how a phenomenon discovered toward the 

 beginning of the XlXth century by a botanist, and named after 

 him Brownian motion, has in recent years yielded the surest 

 evidence we possess of the validity of the kinetic theory of matter. 

 Prom the experimental side the advance has been made in the 

 greater part by Professor Perrin himself and his collaborateurs ; 

 but he has been helped greatly by the theoretic investigations of 

 Einstein and others. Though the evidence from Brownian motion 

 is the most direct, it is confirmed by several independent lines of 

 evidence based on the blue colour of the sky, the law of radiation 

 from an incandescent body, and on radioactivity. All of these 

 methods give concordant and precise indications of the dimensions 

 and number of the atoms which play ihe important role in the 

 kinetic t.eory. The work possesses the attractive feature that it 

 is quite modern, and this lirtle volume constitutes a very suitable 

 introduction ro the subject. It is semi-popular in character; any 

 mathematical results are merely summarized. Bui it is at the 

 same time a very scientific treatise though of an elemen'ary 

 kind. 



Phil. Mag. S. 6. Vol, 25. No. 150. June 1913. 3 N 



