1818.] of the Strata of the Environs of Paris. 283 



guished throughout by its tenacity, its spathose parts, or by a tex- 

 ture which, though not completely spathose, approaches nearly to 

 the crystalline state, and by the abundance and variety of its fossils, 

 which consist, besides the ostrea of the pays de Bray, of other 

 species of considerable size of the families of ostraceas, of byssi- 

 feri, and of trigoniae, many zoophites, particularly madreporse, 

 &c. This limestone is every where near to, or accompanied by, 

 the lower clays of the chalk ; but in no part can we see its geolo- 

 gical position better than in the escarpment called the Vaches 

 noires, on the coast between Honfleur and Dives. It there forms 

 some beds of various degrees of thickness, placed in the midst 

 of two deposits of grey marly clay. The upper deposit often 

 contains chlorite in blackish green grains, and passes into the 

 chalk with chlorite which is immediately incumbent on it. The 

 lower clay is characterized by the gryphea latissima, and lies on 

 the oohte limestone, which has a slaty structure in its upper beds, 

 and extends towards Caen. 



Article VIII. 



Observations on M Bendant's Memoir " Sur la Determination 

 des Especes Minerales." By W. H. Wollaston, M.D. F.R.S. &c. 



(To the Editors of the Annals of Philosophy ) 

 GENTLEMEN, 



Understanding that you are about to oblige the reader* 

 of the Annals of Philosophy with an abstract of M. Beudant's 

 valuable memoir " Sur la Determination des Especes Minerales," 

 I am in hopes that you will deem a few observations that I have 

 made on the crystalline forms of those metallic sulphates, which 

 were the subjects of M. Beudant's experiments, deserving of 

 publication along with his memoir. 



I must own that I felt considerable doubt of the accuracy of 

 his observations with respect to those crystals which he found 

 to resemble sulphate of iron ; as it appeared to me that he has 

 not a just conception of the form of that salt, when he speaks 

 of it as crystallizing in rhomboids. 



That the form of this salt is an oblique angled parallelepiped 

 cannot be questioned, and that all the acute, or obtuse angles 

 are nearly equal is very obvious ; but on examining the modifica- 



frora underneath these bed-, first of the lias, then of the marbres de marquise, which 

 I consider to belong to the old alpine liraeotone, or zechstein of the Germans, and, 

 lastly, of the coal strata. The last soon disappear under the chalk, which border* 

 this small region in the form of a semi-circular chain of hills. It is consequently 

 proper to remark that I was incorrect in 1808 (Journal des Mines, torn. xiiv. 

 p. 34ft) in referring the limestone of the Koulonais, which I had not 6een myself, 

 to the transition formation of the north-east of France. 



6 



