536 Dr. T. Sterry Hunt — On Italian Geology. 



characteristic elements of these rocks, and do not come from great 

 depths. The porphyries and the granites, which are found so 

 frequently in this zone, are not intruded rocks, since they do not 

 traverse the underlying gneiss, but of sedimentary origin, like the 

 limestones, the calcareous and ai'gillaceous schists which accompany 

 them. These are points upon which it seems to me important to 

 insist. 



"At Chaherton, a mountain of the Cottian Alps, I found resting 

 directly upon the serpentinic series a semi-crystalline limestone 

 holding organic remains. Not then suspecting a hiatus in the 

 succession, I was led to suppose that these fossils, which were badly 

 preserved, might be very ancient, and my friend Michellotti, who 

 was so good as to study them, thought like myself that they were 

 Lower Palaeozoic forms. Upon these fossils I have published two 

 papers.^ It appears, however, that our notion of the existence of 

 Silurian [Cambrian] forms in the Alps was an illusion.^ I sub- 

 sequently discovered more complete sections in the valley of the 

 Macra, and in that of the Stura de Caneo (Maritime Alps), and in 

 these, in limestones which appear to be a continuation of those of 

 Chaberton, we have found a good number of fossils which have been 

 described by Messrs. Zittel and Giimbel, and show the existence in 

 the Alps, above the zone of the pietre verdi, of various Mesozoic and 

 C^nozoic terranes. Eesting upon the crystalline rocks we have, first 

 a quartzite alternating with a semi-crystalline limestone, then a 

 compact limestone with layers of anthracite, followed by another 

 compact limestone of Triassic age, with Encrinurus UUiformis, and 

 finally by a series of limestones, Liassic, Jurassic, and Cretaceous ; 

 the whole overlain by Nummulitic and more recent Tertiary strata. 

 The complete succession is then (1) The ancient central or jorimitive 

 gneiss, with quartzite, crystalline limestone, graphite, etc. (2) The 

 pietre verdi series, princijoally formed of serpentine, Iherzolite, 

 euphotide, diorite, variolite, porphyry, calc-schists, apenninite, etc. ; 

 (3) The anthracitic series ; (4) Triassic ; (5) Liassic ; (6) Jurassic ; 

 (7) Cretaceous ; (8) Nummulitic, Miocene, Pliocene." [This is 

 illustrated in the letter by an ideal section.] 



" The excursions which I have lately made in the Apennines of 

 Prato in Tuscany, and in the Ligurian Apennines, had for their 

 object to study the serpentines of these regions. Some geologists 

 of my acquaintance have lately given themselves much labour and 

 pains to confute my views of the age and the nature of the serpentines. 

 They wish to establish that these are eruptive rocks, in many cases 

 interstratified with the beds of the Upper Eocene — a proposition 

 which is wholly untenable. The serpentines as well as the other 

 rocks of the pietre verdi series are ancient rocks, pre-Silurian in age, 

 and are of types which have not been formed in later times. In 

 regarding these from this point of view, the geology of all those 



^ Sul fossili del calcare dolomitico del Chaberton ; Eoma, 1876. Su alcuni fossili 

 paleozoic! dalle Alpi marittimi et dell' Apennini ligure ; Eoma, 1877. 



^ In Sardinia, however, Lower Palaeozoic forms, both Cambrian and Ordovician, are 

 met with ; Mineral Physiology and Physiography, p. 476. 



