Geology. 473 



esting way of the apparent form of the sky, its causes and its 

 consequences. It is to be shortly followed by three others, treat- 

 ing, respectively, of the phenomena due to the aeriform compo- 

 nents of the atmosphere, of those due to the exceptional presence 

 of foreign bodies (halos, coronas, etc.), and of those attributable 

 to the constant presence of small particles. c. s. h. 



13. Instruments et 3Iethodes de Mesures J&lectrique Industrielles ; 

 par H. Armagnat. Deuxieme Edition, revue et completee, 599 

 pp. Paris, 1902 (C. Naud). — The first part of this useful book, 

 constituting a half of the whole volume, contains a general 

 description of the familiar laboratory instruments for electrical 

 measurements and of their modes of use. Excellent features of 

 the discussions are the statements concerning the limiting accu- 

 racy of the various methods. The second part, occupying about 

 one hundred pages, is devoted to industrial appliances for electri- 

 cal measurements. The remainder of the volume, constituting 

 the third part, is given to a description of the methods employed 

 in electric and magnetic measurements, both refined and indus- 

 trial. It is in this part that the ordinary reader will find most 

 that will appear novel to him. The volume as a whole is clearly 

 written, clearly printed, and adequately, if not admirably, illus- 

 trated, c. s. H. 



14. Note on the Size of 'Nuclei ; byC. Barus. (Communicated.) 

 — If in case of nuclei produced by shaking solutions, we regard 

 the nucleus as so constituted, that a central electron forms a 

 closed field with the charge due to friction uniformly distributed* 

 over the surface ; if, moreover, the excess of vapor pressure at 

 a surface of radius JR is eventually equal to the electrical sur- 

 face pressure, we may write 2Tp/li=z X-n-e 2 / (XQ^B^K) ; whence 

 H 3 z= e 2 / (\QirTpK), where e is an electron (7xl0~ 10 electrostatic 

 units), I 1 the surface tension of water (81), p its vapor density 

 (17xl0~ 6 ), J'Tits specific inductive capacity (80). From this fol- 

 lows for the radius of the nucleus M = 4*5 X 10~ 7 , which (in the 

 light of other data to be adduced at length elsewhere) seems to be 

 a reasonable value. A nucleus smaller or larger than this will 

 either grow or evaporate, respectively, to the critical radius here 

 implied. 



II. Geology. 



1. Geological Survey of Canada, Summary Report of the 

 Geological Survey department for the Calendar year, 1901 / by 

 Robert Bell, Acting Deputy Head and Director. 269 pp. — 

 Since the death of the late director of the Canadian Geological 

 Survey, Dr. G. M. Dawson, March 2, L901, the administration 

 has been in charge of Mr. Robert Bell. The appropriation for 

 the year was $115,900. There were 31 parties in the field dur- 

 ing the summer season, and 12 publications were completed and 

 issued. Among the important investigations were those of 



* As, for instance, by rotation. 



