Southern Flank of the Tyrolese Alps nearBassano. 277 



naturalists are still disposed to adhere to the old opinion, 

 that the forces which gave to the secondary rocks tit ir actual 

 configuration, had entirely ceased to act before the deposition 

 of the tertiary strata. The following sections, which I made 

 last autumn on the southern flank of the Alps near Bassano, 

 appearing to throw light on this curious and important point, 

 no apology is requisite for presenting them to the considera- 

 tion of geologists ; indeed, any details of the structure of dis- 

 tant groups of the tertiary deposits must be considered of high 

 interest when it is stated, that on the sides of the Aips and 

 Apennines they fully rival in thickness our most - jitant 

 secondary formations in England. This particular group, 

 however, near Bassano, is not offered as the type of all the 

 other tertiary deposits of the north of Italy, where their varia- 

 ble characters may still form the subject of other communica- 

 tions from Mr. Lyell and myself. 



The tertiary or subalpine deposits, which to the west of the 

 Brenta are so much traversed by basaltic and trap rocks, are 

 entirely free from them in this district be ween the rivers 

 Brenta and Piave, where they swell into hills of considerable 

 importance, occupying between Asolo and Possagno a breadth 

 of four or five miles. Here, as in many other parts of the 

 north of Italy, they form two great natural divisions : — 



1st. An exterior zone composed of conglomerates, with sub- 

 ordinate beds of yellow sand and blue marl, containing shells, 

 the greater number of which are found in the subapennine 

 formations described by Brocchi, and amongst which a con- 

 siderable proportion of the species are identical with those of 

 the present sea*. 



2ndly. An inferior system of green and yellow calcareous 

 sandstone, blue shell marl and compact limestone, some of 

 which are distinguished by nummulites. These latter beds 

 rest upon the scaglia (or equivalent of the chalk), which rising 

 into the Alps passes into a dolomitk; limestone of the oolitic 

 series. 



Explanatory of these relations, I now proceed to detail two 

 sections in a descending order: the first from Asolot to Pos- 

 sagno at the foot of the Alps ; the second from Bassano to 

 Campese at the mouth of the Canal di Brenta, where that 

 river issues from the Tyrol. 



* This zone is the equivalent of the subalpine conglomerates and marls 

 near Nice, which Mr. Risso was the first to identify with the subapennine 

 formations of Brocchi. 



t Fortis in his " Memoircs," vol. i. p. 144, gives a slight sketch of the dis- 

 trict of Asolo, hut without any attempt to explain its geological relations 

 He however describes " Madrepore fungitcs" in blue marl at Castel Cucco; 

 Turbinites terebra and editus of lirander, fig. 47; Dcntalium, Murex or 

 ditto; Helix mutabilis, Brander, fig. 58 j and other shells in the Val d'Ur- 

 <rana. His figures of IheMadrepora fungites are very characteristic. — P. 147. 



