.254 Professor John W. Judd [Jan. 30, 



published in a medical journal, do not however seem to have attracted 

 much attention from the physicists and chemists of the day. 



Lavalle, between the years 1850 and 1853,* and Kopp in the year 

 1855,t made a number of valuable observations bearing on this 

 interesting property of crystals. In 1856 the subject was more 

 thoroughly studied by three investigators, who published their results 

 almost simultaneously — these were Marbach,| Pasteur,§ and Senar- 

 mont.|| They showed that crystals taken from a solution and muti- 

 lated in various ways, upon being restored to the liquid, became 

 completely repaired during subsequent growth. 



As long ago as 1851, Lavalle had asserted that when one solid angle 

 of an octahedron of alum is removed, the crystal tends to reproduce 

 the same mutilation on the opposite angle when its gi'owth is 

 resumed. The phenomena observed have, by some subsequent 

 writers, however, been explained in another way to that suggested by 

 the author of this experiment. In the same way the curious experi- 

 ments performed at a subsequent date by Karl von Hauer — experiments 

 which led him to conclude that hemihedrism and other peculiarities 

 in crystal growth might be induced by mutilation, H — have been 

 asserted by other physicists and chemists not to justify the 

 startling conclusions drawn from them at the time. It must be 

 admitted that new experiments bearing on this interesting question 

 are, at the present time, greatly needed. 



In 1881 Loir demonstated two very important facts with regard 

 to growing crystals of alum.** First, that if the injuries in such a 

 crystal be not too deep, it does not resume growth over its general 

 surface until those injuries have been repaired. Secondly, that the 

 injured surfaces of crystals grow more rapidly than natural faces. 

 This was proved by placing artificially cut octahedra and natural 

 crystals of the same size in a solution, and comparing their weight 

 after a certain time had elapsed. 



The important results of this capacity of crystals for undergoing 

 healing and enlargement, and their application to the explanation of in- 

 teresting geological phenomena, has been pointed out by many authors. 

 Sorby has shown that, in the so-called crystalline sand-grains, we 



* Bull. G^ol. Soc. Paris, 2nd ser., vol. viii. (1851), pp. 610-13; Moigno, 

 Cosmos, ii. (1853) pp. 454-6 ; Compt. Kend., xxxvi. (1853), pp. 493-5. 



t Liebig. Ann., xciv. (1855), pp. 118-25. 



X Compt. Eend., xliii. (1856), pp. 705-6, 800-2. 



§ Ibid., pp. 795-800. 



il Ibid., p. 799. 



^ Wien. Sitzungsber., xxxix. (1860), pp. 611-22; Erdmann, Journ. Prakt. 

 Chem., Ixxxi., pp. 356-62; Wien. Geol. Verliandl., xii. pp. 212-3, &c. Compare 

 Frankenheim, Pogg. Ann., cxiii. (1S61); Fr. Scharff, Pogg. Ann., cix. (1860), 

 pp. 529-38; Neues Jahrb. fiir Min., &c., 1876, p. 24; and W. Saubcr, Liebig. 

 Ann., cxxiv. (1862), pp. 78-82 ; also W. Ostwald, Lebrbuch d. Allg. Chem. (1885), 

 Bd. i., p. 738 ; and O. Lehmaini, Molekular Physik (1888), Bd. i. p. 312. 



*♦ Compt. Rend., Bd. xcii. p. 1166. 



