Geological Society. 135 



Gibraltar ; but this supposition the author conceives to be impro- 

 bable. 



II. Tertiary rocks consisting of sand, sandstone, and a conglo- 

 merate of various rolled pebbles, shell marl, calcareous gritstone 

 and breccia, and gray marl, occupy an extensive area on the west 

 and north-west of Nice. 



The shell marl here mentioned is that which Brocchi has described ; 

 and it contains in the Sub-Alps the same fossils as in the Sub-Appe- 

 nines. 



In the calcareous breccia are angular pieces of the contiguous 

 limestone and dolomite perforated by lithodomi ; adhering to which 

 are sometimes found the lower valves of spondyli, quite perfect, not- 

 withstanding the delicate texture of their edges. The cement con- 

 tains three species of pecten ;— with remains, perhaps, of a Saurian. 

 Care must be taken not to confound this latter breccia, which rises 

 more than a thousand feet above the sea, with the diluvial breccia 

 above described. 



On reviewing the tertiary beds, the author remarks in their history 

 three distinct epochs ; viz. two of repose, and one of violent distur- 

 bance. 



2. The Secondary rocks of Nice consist of two great formations ; 

 the upper one composed of siliceous, argillaceous, and calcareous par- 

 ticles intimately mixed, but in very variable proportions ; some of the 

 beds abounding in green grains ; which circumstance, together with 

 the nature of their fossils, induces the author to rank the formation 

 to which they belong with the greensand of England. Nummulites, 

 however, which are rarely found in the greensand of this country, 

 are found plentifully in that of Nice*. The strata are very much dis- 

 turbed and contorted ; so that an unguarded observer might often 

 suppose them to be inferior to rocks on which they are in reality in- 

 cumbent. 



The greensand is succeeded by a lower formation, which the author 

 refers to the Jura-limestone or oolite. In this he has found, occasion- 

 ally, terebratulee j in addition to which, it is said by Mr. Allan to 

 contain ammonites, pectens, an echinus, and, near the lighthouse at 

 St. Hospice, numerous corals. In mineralogical character, this stra- 

 tum is very unlike the English rocks which it is supposed to repre- 

 sent, its principal members being compact limestone, with occasion- 

 ally, flint, dolomite, and gypsum. The dolomite and compact lime- 

 stone are intimately connected; but the connection of these two 

 beds with the gypsum is less evident. At Sospello the gypsum 

 affords numerous small crystals of carbonate of magnesia or dolo- 

 mite ; but both these substances are found in too many formations 

 to be considered as characteristic. 



The compact limestone, dolomite and gypsum of Nice are most 

 analogous to those of the Tyrol, Carinthia, Stiria, and the North of 

 Italy ; in regard to the history of which, M. Von Buch has supposed 

 that what is now dolomite, was not so in the first instance ; and that 

 the magnesia contained in it has been absorbed from pyroxenic lava, 

 by the forcible intrusion of which both this and the contiguous rocks 



• See Phil. Mag. and Annals, N. S. vol. iv. p. 235. 



have 



