202 SERPENTINE. 



derived from its peculiar texture, so often earthy, and 

 so seldom crystalline. The same character is frequent 

 in the rocks of the trap family ; and whether it is a 

 consequence of partial decomposition, as there sug- 

 gested, or an original form, it is obvious that the same 

 difficulty applies to both. 



An observation of Brongniart, imperfectly made, and 

 therefore at first disputed, becomes explained under 

 more accurate observation consequent on the views 

 which I originally suggested, while it tends to con- 

 firm the theory which I have given of Serpentine. 

 The error and its correction will serve to teach the 

 young observer the necessity of preliminary and cor- 

 rect knowledge. In various parts of the Apennines, 

 as at Prato, Pietramala, Volterra, &c., it was found 

 lying above Diallage rock, followed downwards by 

 jasper and by the secondary limestone ; while he con- 

 cluded that the serpentine of La Bocchetta, Mussinet, 

 Baldissero, and Castellamonte, was similarly situated. 

 Hence, not only Serpentine, but diallage rock, and 

 jasper also, ought to be secondary rocks of a very late 

 date. Admitting the facts, in their fullest extent, I 

 had thus explained them. I have elsewhere shown 

 that jasper is sometimes a member of the trap family, 

 and that it is often peculiarly associated with these 

 rocks, when belonging to the stratified substances with 

 which they are in contact. If instances of secondary 

 and unstratified diallage rock did not exist, its analogy 

 to hypersthene rock is so great, that such a fact 

 would excite no surprise. It only remained to account 

 for the Serpentine ; and as I have shown it to be con- 

 nected with trap, in the case of veins, the same rule 

 might be extended to the masses in question. Thus the 

 upper rocks of this series should be a secondary for- 

 mation belonging to the trap family ; the jasper being 



