Notice of Active and Extinct Volcanos. 255 



Mount Bolca. 



"I am now arrived at one of the principal objects of my work, 

 that is to say, the crisis, when 1 shall determine, with some 

 probability, to what epoch of formation, the celebrated locality 

 of fossil fish at Mount Bolca ought to be referred. 



"■ I shall not attempt to describe this mountain, or rather this 

 collection of very high hills ; I have not studied it sufficiently to 

 induce the hope that I could give a description of it, which would 

 be more complete than that given by the naturalists who have 

 made it known : but I think nevertheless, that I shall be able to 

 distinguish the characteristic traits of the formation to which it 

 belongs. It will suffice, therefore, to fix these characters, to 

 give a short account of the quarry which I visited, or rather to 

 give an explanation of the section which I have made of it. 



" It is known that the quarries of ichthyolites are situated to- 

 wards the summit of the hills which are to the south east of 

 Mount Bolca, and which descend towards Vestena-Nova. In gen- 

 eral the base of these hills towards the east, that is to say, towards 

 the vallies of Chiampo, has appeared to me to be composed of a 

 compact limestone, amygdaloidal, reddish and analagous in its 

 structure to the marble known under the name of Verona marble 

 or .limestone, which in the Euganean mountains is evidently infe- 

 rior to the trachyte and other felspathic rocks of these moun- 

 tains, which include some ammonites, and which seem to me to 

 possess the most of the characters belonging to the Jura lime- 

 stone. Upon these beds of limestone, and as it were issuing from 

 their bosom, are some very elevated and extensive hills, compo- 

 sed of almost all the species and varieties of trap rocks, the spi- 

 lite, the basanite, the brecciole, which are scattered about either 

 without any order, or in an order which I was unable to discover. 

 These trap rocks, existing here upon a grand scale, elevated and 

 extensive, alternate, especially, towards the highest parts of the 

 hills, and of course with their most superficial parts, with some 

 beds of a limestone, often calcareous or marly, which are equally 

 extensive : this is the limestone which contains the fossil fish, 

 and this is the limestone, of which the point is to determine the 

 epoch of its formation. Finally, the highest summits and parti- 

 cularly that called la Purga di Bolca, are crowned with basalt, 

 which seems of course to cover the preceding rocks, and which, 

 in fact, does cover them very often, without any doubt. Such is 

 the general disposition of the rocks in the mountains which com- 

 pose the group of which Bolca makes the principal elevation. 

 The following description will make known the particular dis- 

 position of these rocks in some cases. 



" The ichthyolite hill which I have visited, and of which I 

 here give a drawing, in section, but without exact proportions. 



