1824.] Scientific Notices— Chemistry. 467 



used in our public buildings. The Isle of Portland consists of a 

 mass of limestone lying upon a bed of bituminous clay and 

 limestone identical with the Kimmeridge beds. The lower and 

 more considerable part of the limestone in the Isle of Portland 

 above the Kimmeridge clay, is chiefly oolitic, and contains 

 beds of chert ; but the upper part consists of a yellowish calca- 

 reous stone nearly compact, which contains in it a bed of earthy 

 lignite abounding in silicified portions of trunks of trees, about 

 two or three feet in length, some of which are erect, and others 

 lie flat. As far as he could ascertain, the fossil wood was 

 nearly confined to this stratum, and is not dispersed through the 

 oolite as had hitherto been supposed. These upper beds of the 

 Isle of Portland he considered as belonging to the same forma- 

 tion as the Purbeck beds, having found some very similar in the 

 Isle of Purbeck. 



Considering the fossil shells of the Portland oolite to be 

 marine, while those of the Purbeck limestone are chiefly fresh- 

 water, together with the great difference in the mineralogical 

 character, the author stated his opinion that these two series of 

 beds should be kept in separate groups in classing the English 

 strata. 



Article XV. 

 SCIENTIFIC NOTICES. 



Chemistry. 

 1 . Minerals produced by Heat. 



It has been very often observed, that the analyses of minerals 

 are of comparatively little value, as long as we are not capable 

 of reproducing by composition what had been dissolved.^ Prof. 

 Mitscherlich has accomplished this important object. We have 

 been gratified by the sight of beautiful and well-defined crystals 

 of greyish white pyroxene, which had been obtained by mixing 

 the constituent parts indicated by analysis in the necessary 

 proportion, and exposing this mixture to the high degree of heat 

 of the porcelain furnaces of Sevres. By this means, Prof. 

 Mitscherlich has succeeded in obtaining several species that 

 occur in nature. He has likewise observed among the different 

 kinds of slags more than forty species in a crystallized state, 

 particularly of such minerals as are found in primitive rocks, but 

 likewise a good many others which have not hitherto been 

 observed. We propose giving in oar next number a full state- 

 ment of the further details of these most important experiments. 

 — (Edin. Jour, of Science.) 



2. Berzelius's Analysis of the Sulphato-tri-carbonate of Lead. 



This eminent chemist, in analyzing some specimens of this 



2 n 



