,^1 Theory of Gryjlallifation. 



of two thoufand and forty-four different forms : a number 

 which exceeds more than fifty times that of the forms al- 

 ready known*, and if we admit into the combination de- 

 crements by three and four ranges, calculation will give 

 8,388,604 poflible forms in regard to the fame fubftance. 

 This number may be {till very much augmented in confe- 

 quence of decrements either mixed or intermediary. 



The ftriae remarked on the furface of a multitude of cryf- 

 tals afford a new proof in favour of theory, as they always 

 Jhave directions parallel to the projecting edges of the laminae 

 of fuperpofition, which mutually go beyond each other, un- 

 lefs they arife from fome particular want of regularity. Not 

 that the inequalities refulting from the decrements muft be 

 always fenfible, if the form of the cryftals had always that 

 degree of finifhing of which it is fufceptible ; for, on account 

 of the extreme minutenefs of the moleculae, the furface would 

 appear of a beautiful polifh, and the ftriae would elude our 

 fenfes. There are therefore fecondary cryftals where they are 

 not obferved in any manner, while they are veryvifible in other 

 cryftals of the fame nature and form. In the latter cafe, the 

 action of the caufes which produce cryftallifation not having 

 fully enjoyed all the conditions neceflary for perfecting that 

 fo delicate operation of nature, there have been ftarts and 

 interruptions in their progrefs, fo that, the law of continuity 

 not having been exactly obferved, there have remained on the 

 furface of the cryital vacancies apparent to our eyes. In a 

 word, it is feen that fuch fmall deviations are attended with 

 this advantage, that they point out the direction according 

 to which the ftriae are arranged in lines on the perfect forms 

 where they efcape our organs, and thus contribute to unfold 

 to us the reaj meehanifm of the ftrudture. 



The fmall vacuities which the edges of the laminae of fu- 

 , perpofition leave on the furface of even the moft perfect fe- 



* In my Efiay, p. 217 et fcq. I carried the number of thefe forms only 

 to 1019, becnufe I had not introduced as an element in my calculation 

 modification of the law of decrements, with the exiilence of which I 

 set then acquainted. 



