292 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 13, 



Micaceous sandstone, which I beheve to be of miocene age, with traces 

 of stems of plants, appears in the conical hillock near Monte Catini ; 

 but the strata are there so dislocated in their relations to serpentine 

 and gabbro, that no distinct order is visible. It was the belief of 

 Professor Pilla, that much of the argillaceous and sterile marl of the 

 deep denudations around Volterra, particularly the lower portion 

 which contains large masses of gypsum and salt-springs, is also of 

 miocene age. Of this there are no fossil proofs of which I could 

 hear. It is, however, certain that the thick unfossiliferous marls are 

 surmounted by others, and finally by yellow sands and sandstone, the 

 ** panchina," on which stands the noble ancient city of Volterra. 

 These are true subapennine beds with many fossils ; the tombs of the 

 Necropolis being excavated in the sandy " panchina." 



Pomerancia, to the south of Volterra, is placed on a high plateau 

 of shelly tuff, which probably pertains to the upper portion of the 

 pliocene, but the mountains to the east and south are macigno and 

 alberese (possibly of cretaceous age ?), mth nuclei of still older rocks. 

 Not now adverting to these rocks, or to the hot springs issuing 

 through them which afford the boracic acid*, I vdll briefly notice 

 the coal deposits of Monte Bamboli and Monte Massi, which lie still 

 further to the southward. These deposits are described by Savi and 

 Pilla, and the coal has been analysed by Matteucci. For my own 

 part, I consider them to be of about the same age (miocene) as the 

 coal of Caddibuona in Piedmont and of Fuveau near Toulon in the 

 south of France f. 



At Monte Bamboli the coal-seams, varying from eighteen inches 

 to five feet and inclined about 30°, rest on earthy and broken schists, 

 which are so nearly in contact with the surface of the so-called 

 alberese of this tract, that I could scarcely divest myself of the idea 

 that the one had succeeded conformably to the other ; but although 

 the upper schists or galestri of the alberese appeared to graduate into 

 the gritty schist and the latter into the coal-seams, the whole dip- 

 ping to the W.S.W., I was subsequently led to believe, from the 

 sections at Monte Massi, that the apparent conformity is accidental. 

 The coal, of which there are here two courses, is interlaced with a 

 band of an earthy, shelly, freshwater limestone with mytili ; and 

 the surface of the coal-seams, in which plants and shells occur in 

 a schist or " bat," graduates up into a considerable thickness of a 

 thin, flat-bedded, sandy, impure limestone, which is followed by an 

 indurated clay rock, and the latter by a coarse conglomerate. Whilst 

 the coal-beds dip 30° S.W. in the shaft west of the works, they may 

 be observed in the side of the torrent north of the engine to roll over 

 to the N.N.E., and in one spot they dip 70°. In these dislocations 



* In reference to the various, intensely hot springs which afford the boracic salt, 

 I will only here say, that they seemed to me to issue from fissures having a direc- 

 tion from north and by west to south and by east, and that these parallel linear 

 outbursts thus seem fairly to represent the last remnants of that grand subter- 

 ranean evolution of heat which in former ages has so affected all this range of the 

 Maremma. 



t See description of this coal-field by Sir C. Lyell and mvself, Proc. Geol. Sqc, 

 vol. i. p. 150. 



