488 Prof. Bichards and Mr. Archibald : A Study of 



The extreme values of #/V experimentally obtained were 

 #/V=*10 in series 3 and #/V = '16 in series 4. Hence the 

 values n = l'b x 10 4 and ?? = 2*4 x lO 1 are computed for these- 

 extremes. Recalling that 4 x 10 4 is the number of particles 

 per cubic centim. inferred for complete saturation, and that 

 n is the number at the initial section of the condenser con- 

 tiguous to the hard-rubber plug, where many ions must already 

 have vanished by absorption, I hold the value of n stated to- 

 be in reasonable accord with the theory sketched in §§ 6-8, 

 and throughout the course of the present papers. 



Brown University, Providence, U.S.A. 



XL VIII. A Study of Growing Crystals by Instantaneous 

 Photomicrography. (Contributions from the Chemical 

 Laboratory of Harvard College.) By Professor Theodore. 

 William Richards, of Harvard University, and Ebenezer 

 Henry Archibald, A.M., 1851 Exhibition Scholar of 

 Dalhousie University *. 



[Plates VII.-IX.] 



C10UNTLESS observers have watched the growth of 

 ^ crystals under the microscope. As long ago as 1839 

 attempts were made to study also the birth of crystals, in order 

 to determine in what manner the new phase makes its entrance 

 into the system. With a microscope magnifying 600 

 diameters, Linkf thought he could detect the formation of 

 minute globules at the moment of precipitation — globules 

 which soon joined and assumed crystalline form. Schmidt J,. 

 Frankenheim§, and especially Vogelsang ||, made similar 

 observations some years later, and several more recent 

 accounts of this phenomenon have appeared. Modern in- 

 vestigators have been more concerned with the speed of 

 separation from supersaturated or supercooled liquids than 

 with the form of the first separation H. 



* Reprinted from the Proceedings of the American Academy of Arts 

 and Sciences, xxxvi. p. 341 (1901). From a separate impression commu- 

 nicated by the Authors. 



t Link, Pogg. Ann. xlvi. p. 258 (1839). 



j Schmidt, Lieb. Ann. liii. p. 171 (1845). 



§ Frankenheim, Pogg. Ann. cxi. p. 1 (1860). 



|| Vogelsang, Die Krystalliten (Bonn, 1875). See Lehmann, Mole- 

 cularphysik, i. p. 730 (1888). 



% Gernez. Compt. Rend. xcv. p. 1278 (1882) ; Moore, Zeits. phys. 

 Chem. xii. p. 545 (1893) ; Friedlander & Tammann, ibid. xxiv. p. 152 

 (1897) ; Tammann, ibid. xxv. p. 441 ; xxvi. pp. 307, 367 ; xxviii. p. 96 ;. 

 Kiister, ibid. xxv. p. 480 ; xxvii. p. 222 ; Bogajavlensky, ibid, xxvii. 

 p. 585. 



