of Serpentine, SfC. in the Apennines. 177 



2dly. Beneath this diallage rock a red bed (C) is seen, 

 of nearly equal thickness throughout its whole extent, 

 almost horizontal, or very little inclined towards the North. 

 It is jasper in thin and nearly parallel beds. It is princi- 

 pally red, yet is occasionally mixed with greenish zones. 



enormous masses evidently detached fi'om the unstratified but broken 

 blackish summits of this small chain of mountains ; they are so volu- 

 minous that, if sufficient attention is not paid to it, it might be thought 

 that tliese masses of serpentine rocks were in place, and that they were 

 beneath the limestone; it was a remark I made on the spot to my young 

 companions, M. Bertrand-Geslin and my son. But M. Mesnard de la. 

 Groye has supplied what may be wanting, by communicating to me with 

 a generous eagerness the specimens he collected on the summit of this 

 mountain. They have shewn me that there occurred in these well cha- 

 racterised serpentines very remarkable veins of crystalline quartz, con- 

 taining pyrites ; as also a hornblende diallage rock, in which the petro- 

 silex, the diallage, the hornblende, and even the serpentine are perfectly 

 distinct; lastly a porphyritic rock, traversed by very singular calcareous 

 veins, and which unites the serpentine formation to that of porphyries. 

 Whether this serpentine rock is less abundant in serpentine than the 

 others, as I suspect, or that it even passes into greenstone, it does not 

 the less belong to what geologists call the second serpentine formation. 

 M. von Buch, in the examples he gives of gabbro, i. e. of this formation, 

 cites Covigliauo; and in the MS section he has made and confided to me, 

 he places a summit of serpentine in this spot. 



The association of serpentine or steatite with hornblende is well recog- 

 nised, and referred, like the serpentines, to the transition series. M. 

 Stifft mentions, to the S.W. ofNeubourg, a thick bed of steatite on an 

 altered sediment basalt, accompanying greenstone, placed on transition 

 limestone, near Herborn (Leonhard, tasch : 1808, p. 216.) M. Daubuis- 

 son also admits this association, and remarks that the passage from ser- 

 pentine to hornblende is often insensible. M. de Bonnard equally brino^s 

 forward, as an admitted fact near Hartzburg, in the Hartz, the passage 

 of diallage rock into greenstone, by a diallagic greenstone, &c. 



The rock on which M. Palassou has written so much, which he names 

 Ophite, and which is actually a greenstone, passes into serpentine and- 

 hornblende diallage rock ; it belongs, as he himself has remarked, and I 

 have had occasion to observe near Pouzac, to the serpentine formation, 

 and he insists that it rests on a secondary limestone.* 



♦ Dr. MacCulloch remarks in his account of serpentine, (Classificatioa 

 of Rocks, p. 245), " That when the contact is that of hornblende rock 

 with serpentine, a perfect gradation may sometimes be traced." H& 

 states two examples have been seen by him of serpentine in the second 



