200 DR. THOMAS STERRY HUNT ON THE 
pentines, and upon the importance of discovering the centres of eruption through the pre- 
existing strata, “ or at least some positive evidences of such centres.” 
§ 95. I have thought it desirable to reproduce with some detail this ingenious hypo- 
thesis, with Pellati’s comments thereon, for the reason that it shows clearly the difficulties 
which recent observers have found in accepting the older theory of the igneous eruption 
of ophiolites, and moreover brings clearly into view many points which are of importance 
for the solution of the problem before us, of the true relations of these ophiolites to the 
surrounding strata. In view of the fact that the resemblance between the supposed eocenic 
and the eozoic ophiolites is so strong that the two cannot be clearly distinguished or,separ- 
ated from one another, as we have seen alike from the comparisons of Bonney and the 
admissions of the recent Italian geologists themselves (§ 88), it is not surprising that some 
observers like Gastaldi should have been led to look upon the so-called eocene ophiolites as 
nothing more than portions of the underlying eozoic or pre-paleozoic series exposed through 
geological accidents. This explanation becomes more plausible when we reflect that within 
the great basin over which these ophiolites are met with, the paleozoic and mesozoic rocks 
have but a slight development, and are often entirely wanting, the tertiary rocks resting 
directly upon the eozoic pietre verdi. 
§ 96. My own observations of the Italian ophiolites have been limited. I have had, 
however, an opportunity of examining two localities of these so-called eocene serpentines, 
in eastern Liguria and in Tuscany. It was my good fortune in October, 1881, to spend a 
day with Signor Capacci, (whose careful memoir on the region, with map and sections, I 
have already noticed,) in going over Monteferrato in Prato, near Florence, a locality for cen- 
turies famous for its quarries of serpentine, known as verde-prato. About three miles from 
Prato, a town on the railway between Florence and Pistoia, is the little village of Figline, 
which lies on the eastern slope of the ophiolitic mass in question, forming a hill which 
rises boldly from the plain of eocene limestones and shales (alberese and galestro.) The mass 
of ophiolitic rocks occupies an area somewhat oval in form, having, according to the deter- 
minations of Capacci, a length of about 2,600 meters from north to south and a maximum 
breadth of about 1.800 meters. In its highest points it attains elevations of 400 and 426 
meters above the sea, the level of the surrounding plain being about 70 meters. Figline 
itself, where the serpentine appears from beneath the eocene strata lying to the east, is at 
a level of 103 meters, but the similar strata on the western side of the hill, where they 
apparently dip at high angles beneath the serpentine-mass, rise to heights of 295 and 322 
meters above the sea level. 
§ 97. Underlying the alberese, and resting upon the ophiolite along the eastern base 
of the hill, is seen in many places a fine-grained, laminated silicious rock, generally red- 
dish, but sometimes greenish or grey in color, designated as phthanite by the Italian geo- 
logists, which abounds in microscopic forms referred by Bonney in part to polycystinae 
and in part to polyzoa. * This is succeeded, in apparent conformity, by the ordinary type 


* Upon the organic forms found in these and similar silicious or jaspery beds, see a memoir by Prof. Dante 
Pantanelli on the jaspers of Tuscany and their fossils, (I Diaspri della Toscana, ecc. Mem. R. Accad. dei Lincei, 
ser. 3. vol. viii., June, 1880; also Geol. Mag. for the same year, pp. 317,564.) These deposits are found alike at 
various horizons in the upper eocene, and in cretaceous and liassie strata, often in thin layers imbedded in argilla- 
ceous sediments. They consist in part of crystalline and in part of amorphous silica, with oxyds of iron and 
manganese, and contain large numbers of radiolarian forms, of many species, leading the author to conclude with 
de Stefani that they are deep-sea deposits. 


