1815.] Scientific Intelligence. 75 



VII. Chromale of Iron. 



Chromate of Iron occurs in the Bare Hills near Baltimore, in 

 North America, in great ahundance. These hills appear to be 

 serpentine, so that the situation of this mineral is the same in 

 America as in France. The chromate of iron occurs in these hills 

 in three states : 1 . In compact masses of considerable size, mixed 

 with talc, steatite, &c. In this state, which is 1 presume the same 

 nearly with the French chromate, it has some resemblance to brown 

 blende. 2. In grains from the size of a mustard seed to that of a 

 pepper corn, imbedded in steatite. 3. Crystallized in regular 

 octahedrons. The colour of these crystals is black, inclinin"- to 

 steel grey. Surface smooth. Lustre vitreous. Fracture con- 

 choidal. Opake, except some specimens which transmit a blood 

 red . light. Infusible before the blow-pipe, without addition. 

 Magnetic in a considerable degree. Mr. Hayden, from whom this 

 account is taken, believes that many specimens of supposed octa- 

 hedral iron ore are really chromate of iron.* 



VIII. Magnetic Pyrites. 



Stromcyer has lately subjected this mineral to a new analysis, 

 and as he was at uncommon pains to attain the mineral in a state of 

 purity, it is probable that the result which he obtained is a close 

 approximation to the truth. Mr. Hatchett published the first ana- 

 lysis of this mineral, and made us acquainted with its true nature. 

 It was analysed by Proust, and experiments on the artificial com- 

 binations of iron and sulphur were made by Vauquelin. The fol- 

 lowing is the result which they obtained : — 



Iron. 



Hatchett 100 + 57-48 sulphur. 



Proust 100 + CO 



Vauquelin 1 GO + 28-22 



Stromeyer 100 + 67-OS 



If my number for the weight of an atom of iron be correct and 

 if magnetic pyrites be comj)uscd of one atom iron and two atoms 

 sulphur, its constituents should be 



Iron. 



100 + 55-99 sulpliur. 

 This circumstance throws some doul)t iqwn the accuracy of 

 Stroiiieycr's analysis. He informs us, that magnetic pyrites usually 

 contains a mixture of metallic iron and of cubic j)yritcs. Jf this 

 l)c the case, the chance of error in such an analysis was considerably 

 increased. 



IX. ll'liile<tovc. 



Among some minerals which I lately received from Frryberg 

 there is a specimen of the true whiiestone of Werner. This rock 



• Brucc'b y\nieiican Juurnal, No. iv. p. 24.'J. 



