’ 
274 Dr. C. 8S. Du Riche Prelicr—The Tuscan Archipelago. 
on the Permian, but also on the Silurian and pre-Silurian rocks. 
The Lias series is represented in Elba but not in the other islands, 
and gives evidence of another remarkable break, inasmuch as it 
overlies directly the Permian and even the pre-Silurian strata. The 
Upper Lias comprises the metamorphic rocks, felsitic schists, and 
compact and crystalline limestone with garnet and. Wollastonite, 
which are met with on the summit of Monte Cappane, the highest 
point of Elba, where they overlie the granite. Upon the Upper 
Lias strata follow immediately the Eocene rocks, thus marking 
another characteristic gap which is also conspicuous in Corsica as 
well as in the Maremma hills. Indeed in Elba, the Eocene strata 
rest not only on the Lias, but also direct on the pre-Silurian 
formation. They comprise in upward series, nummulitic schists, 
red, green, and grey limestone, followed again by nummulitic lime- 
stone, limestone, schists and sandstone, with numerous and extensive 
dykes of serpentine, gabbro, and diabase. The Eocene serpentine 
frequently appears in close proximity to the ancient serpentine, 
from which it is easily distinguished alike by its different texture and 
location. It is a characteristic feature that the Hocene serpentine, 
gabbro, and diabase of undoubtedly igneous origin always occur 
together in the same superposition. The Upper Eocene strata are 
traversed by great viens of porphyritic granite, and the fact of these 
strata having been proved to be nummulitic and hence Hocene 
proves the further important fact that the intrusive Elban granite, 
which has been so fruitful a source of controversy, is neither 
trachyte, nor liparite, nor felsitic porphyry as it has been called 
by some petrologists, but is a true tourmaline-bearing porphyritic 
granite of Tertiary age. Moreover, the same intrusive granite 
occurs under analogous conditions in the islands of Montecristo 
and Giglio, as well as on the mainland in the Maremma hills. 
Of the metalliferous deposits of Elba, some are found in the 
pre-Silurian, others between the Permian and the Liassic, others 
again between the Permian and Infralias strata, while the workable 
deposits of oxide of iron and the limestone and siliceous rocks with 
which they are associated, are younger than the Eocene sedimentary 
and intrusive rocks already referred to. The Miocene and Pliocene 
strata are absent in the Archipelago with the exception of Pianosa, 
where they bear close resemblance to the Corsican rocks of the same 
age. The post-Tertiary formation is represented in Hlba, Giglio, 
and Pianosa by a coarse calcareous sandstone and a conglomerate 
with marine-shells, which in part edge the coast and in places 
reach a depth of over 600 feet above sea level. The andesites of 
Capraja probably erupted during the same period. 
It is thus seen (1) that the islands of the Tuscan Archipelago are, 
geologically and petrologically, closely connected, not only with 
each other, but with the Maremma hiils on the one hand, and with 
Corsica and Sardinia, as well as with the Ligurian Alps on the 
other; (2) that, therefore, they probably constitute part of a former 
Tyrrhenian continent; and (3) that as a whole, and with a few 
significant exceptions, they are representative of every geological 
pe Pai 
