[page] 59

III. On the COMPOSITION of CHLORITE.

THIS, mineral, described by M. Friedley, had been analysed first by M. Erdmann (Journ. f. prakt. Chem. t. vi. p.89), and afterwards by M. Bonsdorff (Voyage of G. Rose in the Ural, vol. i. p. 252), but with results so different, that M. Rammelsberg suggested that these two chemists had probably analysed different minerals. M. Gerathewohl has lately undertaken the analysis of a specimen named by M. Friedler himself, and the results of this analysis confirm those obtained by M. Erdmann.

	Gerathewohl.	Erdmann.
Silica ..................	24.40	24.93
Oxide of iron.................	30.29	30.05
Alumina..............	45.17	45.02

These results correspond with the formula Si O³, 3 Fe O + Si O³ 3 Al² O³, or rather, Al² O³, 3 Fe O + 2 (Si O³, Al² O³).—Journ. f.

IV. D'ORBIGNY'S 'PALÉONTOLOGIE UNIVERSELLE.'

M. ALCIDE D'ORBIGNY, For. Mem. Geol. Soc., &c., the author of the 'Paléontologie Française,' has undertaken to prepare a work under the above title, in which he proposes to give figures, with accompanying descriptions, of every species of fossil shells hitherto determined, from all geological formations in all parts of the world. It is calculated that the figures will occupy about 1500 plates, which it is intended shall appear in seventy-five numbers, the price of each number, including the letter-press, to be six francs.

The work will be published by Messrs. Gide and Co., No. 5 Rue des Petits-Augustins, Paris.

In a letter* recently received from M. d'Orbigny, he states, "In order to arrive at satisfactory results in an undertaking so vast, I shall need the assistance of all persons who are interested in the advance of geology, and I trust to your procuring for me in England many correspondents willing to exchange the fossil shells of various formations for such portions of my works on Palæontology as they may most require. I wish, for instance, to obtain, 1st, fossils of the Crag and London Clay, and 2nd, those of the Cretaceous formations of the Isle of Wight and Blackdown; but, above all, the fossils of your Carboniferous, Devonian and Silurian beds."

M. d'Orbigny's address is No. 6 Rue St. Hyacinthe St. Honoré, Paris.

* Addressed to Mr. Darwin.