£70 frORMATTON OP BASAITES. 



forms more than tiine tenths of the mass of this sand&tone 

 of Mr. Chevaillers, this effect had not been observed in such 

 a constant manner on such large blocks, as Dolomieu said m 

 speaking of the configuration of basaltes. An effect so fre- 

 quently repeated must have its causes. 



Reflections on the configuration of basaltes. 



Bas-altes first At a time when men were ignorant of the first principles 



supposed a , , ■ ° r . ' 



crystallization, of crystallography, and but few crystals were known, it was 



difficult certainly, to avoid confounding with them solids 

 that exhibited some external appearance of their regularity. 

 Thus Cronstedt,Wallerius, and other celebrated naturalists 

 thought basaltic prisms were the direct products of crystal** 

 lization. 

 Rome de Lisle Rome de Lisle at first adopted the mistake of his prede- 

 nnstake. cessors: but he had scarcely raised the veil, that enveloped 



the mechanism of cvystallization, when he sought for an- 

 other cause of the prismatic division of basaltes, and then 

 the happy idea of a contraction offered itself to his mind. 

 Hauy* But since the genius of Haiiy has developed the theory 



of crystallization in such a learned manner, may we not 

 be astonished still to find naturalists, who are desirous of as- 

 similating basaltic columns with the productions of regular 

 aggregation ? 

 Objection to Setting aside therefore every idea of the crystallization of 

 being^formed 3 ^ saltes - * sbal1 confine myself to the refutation of a slight 

 by cooling, objection of its partizans to the numerous proofs of its 

 contraction, and I shall attempt to follow its mechanism, in 

 examining the laws to which bodies are subjected in cooling, 

 from their re- They admit, that the cooling of the basaltes must have 

 gulanty. occasioned divisions, that would naturally give rise to some 



forms; but they add, that these forms, resulting from 

 chance, and a thousand different accidents, could only be 

 very irregular, and not produce vast columns, as remark- 

 able for their regularity as for the uniform arrangement that 

 characterises their extensive masses, 

 fcut they But why should these forms depend on accidents guided 



ought to be by th e } la nd of chance ? 1 can conceive no reason for this ; 

 e * U af * since, if the cause of the contraction be constant, and if 



the manner in which it. Operates be always the same, ought 



I19t 





