Things not generally Known. 



to bear on the molecular arrangements of matter, he was able 

 to penetrate into the intimate structure of crystals. By this 

 means he proved that the secondary forms of all crystals are de- 

 rived from their primary forms by a regular process of decrement ; 

 and that when a substance is passing from a liquid to a solid 

 state, its particles cohere, according to a scheme which provides 

 for every possible change, since it includes even those subse- 

 quent layers which alter the ordinary type of the crystal, by 

 disturbing its natural symmetry. To ascertain that such viola- 

 tions of symmetry are susceptible of mathematical calculation, 

 was to make a vast addition to our knowledge ; and, by proving 

 that even the most uncouth and singular forms are the natural 

 results of their antecedents, Haiiy laid the foundation of what 

 may be called the pathology of the inorganic world. However 

 paradoxical such a notion may appear, it is certain that sym- 

 metry is to crystals what health is to animals ; so that an irre- 

 gularity of shape in the first corresponds with an appearance of 

 disease in the second. See Hist. Civilization, vol.i. 



REPRODUCTIVE CRYSTALLISATION. 



The general belief that only organic beings have the power 

 of reproducing lost parts has been disproved by the experiments 

 of Jordan on crystals. An octohedral crystal of alum was frac- 

 tured ; it was then replaced in a solution, and after a few days 

 its injury was seen to be repaired. The whole crystal had of 

 course increased in size ; but the increase on the broken surface 

 had been so much greater that a perfect octohedral form was 

 regained. G. H. Lewes. 



Tnis remarkable power possessed by crystals, in common 

 with animals, of repairing their own injuries had, however, 

 been thus previously referred to by Paget, in his Pathology, 

 confirming the experiments of Jordan on this curious subject: 

 " The ability to repair the damages sustained by injury . . . 

 is not an exclusive property of living beings ; for even crystals 

 will repair themselves when, after pieces have been broken from 

 them, they are placed in the same conditions in which they 

 were first formed." 



GLASS BROKEN BY SAND. 



In some glass-houses the workmen show glass which has 

 been cooled in the open air ; on this they let fall leaden bul- 

 lets without breaking the glass. They afterwards desire you 

 to let a few grains of sand fall upon the glass, by which it is 

 broken into a thousand pieces. The reason of this is, that the 

 lead does not scratch the surface of the glass ; whereas the sand, 

 being sharp and angular, scratches it sufficiently to produce 

 the above effect, 



