CRYSTALLOGRAPHY 



CHAPTER I. 



PRELUDE TO THE EPOCH OF DE LISLE AND HAUY. 



f\F all the physical properties of bodies, there is none so fixed, and 

 ^ in every way so remarkable, as this ; that the same chemical 

 compound always assumes, with the utmost precision, the same geo- 

 metrical form. This identity, however, is not immediately obvious ; 

 it is often obscured by various mixtures and imperfections in the sub- 

 stance ; and even when it is complete, it is not immediately recognized 

 by a common eye, since it consists, not in the equality of the sides or 

 faces of the figures, but in the equality of their angles. Hence it is 

 not surprising that the constancy of form was not detected by the 

 early observers. Pliny says, 1 " Why crystal is generated in a hexa- 

 gonal form, it is difficult to assign a reason ; and the more so, since, 

 while its faces are smoother than any art can make them, the pyra- 

 midal points are not all of the same kind." The quartz crystals of the 

 Alps, to which he refers, are, in some specimens, very regular, while 

 in others, one side of the pyramid becomes much the largest ; yet the 

 angles remain constantly the same. But when the whole shape varied 

 so much, the angles also seemed to vary. Thus Conrad Gessner, a 

 very learned naturalist, who, in 1564, published at Zurich his work, 

 De renim fossilium, Lapidum et Gemmarum maxime, Figuris, says," 

 " One crystal differs from another in its angles, and consequently in 

 its figure." And Caesalpinus, who, as we shall find, did so much in 

 establishing fixed characters in botany, was led by some of his general 

 views to disbelieve the fixity of the form of crystals. In his work De 

 Metallicis, published at Nuremberg in 1602, he says, 3 "To ascribe to 

 inanimate bodies a definite form, does not appear consentaneous to 

 reason ; for it is the office of organization to produce a definite form ;' 



1 Nat. Hist, xxvii. 2. * p. 25. ' p. 97 



