Geological Society, 539 



added that the oviparous Vertebrata, whatever may be the nature of 

 their food, have larger blood-corpuscles than Mammalia, and that 

 the size of the blood-corpuscles of many carnivorous birds exceeds 

 that of the corpuscles of several of the omnivorous species. 



Finally, the Two- toed Sloth, which is a purely vegetable feeder, 

 has, excepting the Elephant, the largest blood-corpuscles hitherto 

 observed in any mammiferous animal. 



GEOLOGICAL SOCIETY. 



November 6, 1844. — First Meeting of the Session. The Presi- 

 dent, Mr. Warburton, in the Chair. A paper was read entitled 

 " Observations on the Geology of some parts of Tuscany," by Mr. 

 W. J. Hamilton, M.P., Sec. G.S. 



One of the principal features of the district examined by the 

 author, is the existence of three distinct mountain ridges, extending 

 from N.W. to S.E, by S. parallel to the direction of the main chain 

 of the Apennines, and all belonging to the cretaceous system. The 

 valleys between these ranges are filled with tertiary deposits. Second- 

 ary formations form the greater part of the mountainous district of 

 Tuscan)r, consisting of beds of sandstone, indurated marls and shales, 

 and compact gray lithographic limestone or scaglia. These some- 

 times alternate with each other, and are variously developed in dif- 

 ferent localities. Fossils are rare in all of them. The tertiary for- 

 mations are both marine and freshwater. The marine tertiaries at- 

 tain a height of nearly 1800 feet in the basin of Volterra, where 

 they consist of beds of blue marl and sandy limestones, capped by 

 shelly limestone. Marine shells are frequent in some of these beds, 

 of which the blue marl is the most extensive, attaining in the locality 

 referred to a thickness of nearly 1000 feet. Selenite abounds in part 

 of it ; also beds of rock-salt and alabaster, extensively worked, the 

 mines of the latter by means of regularly constructed mining galle- 

 ries. The other marine tertiary districts are those of Leghorn, Pog- 

 gebonzi. Sienna, and Val de Chiana. Freshwater tertiaries were 

 noticed in two localities, forming limestones as compact and having 

 the aspect of scaglia, but well characterized by their peculiar organic 

 remains. Extensive post-tertiary formations of calctufF occur in the 

 valley of the Staggia and of Elsa, and the beds are in places more 

 than 100 feet thick. The rock called " Gabbro Rosso" by Savi, 

 Mr. Hamilton considers as a metamorphic rock derived from the 

 altered marls and sandstones of the secondary formation, acted oil 

 by the protrusion of igneous rocks of the serpentine class. At the 

 junction of the Serpentine and Gabbro at Monte Catini is found 

 copper oi'e (a sulphuret) extensively worked. Besides the serpen- 

 tine, the quasi-trachytic rock called Selagite, and the basalts of Radi- 

 cofani, are among the igneous rocks of the district. The author con- 

 cludes with an account of the i-emarkable boracic acid works at 

 Monte Cerboli, and of the phsenomena connected with them. 



2 N 2 



