MISCELLANEA. 59 



III. On the Composition of Chlorite. 



This mineral, described by M. Friedler, 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. Ge- 

 rathewohl 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 



99-86 100-00 



These results correspond with the formula Si O^, 3 Fe O + Si O^, 

 3A12 03, or rather, Al^O^ 3 FeO+2(Si03, A12 03).— Towm. /. 

 prakt. Chem. 1845. No. 8. 



IV. D'Orbigny's ' Paleontologie Universelle.' 



M. Alcide d'Orbigny, For. Mem. Geol. Soc, &c., the author of 

 the ' Paleontologie Fran9aise5' has undertaken to prepare a work 

 under the above title, in which he proposes to give figures, with ac- 

 companying 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 ad- 

 vance 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 Palaeontology 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. Honore, 

 Paris. 



* Addressed to Mr. Darwin. 



