454 



PROCEEDINGS OP THE AMERICAN ACADEMY 



verted into nitrates, and separated by Deville's process. The iron and 

 alumina were weighed together as oxides, and the magnesia as the 

 pyrophosphate. The amount and condition of the iron were deter- 

 mined by decomposing the mineral by the process described by the 

 writer in Am. Jour., vol. xliv. page 347, estimating by a standard 

 solution of potassic permanganate the ferrous iron at once, and the 

 total amount of iron after reduction to the ferrous state. Small 

 amounts of lithium and potassium were found by the spectroscope 

 in the residue obtained in Smith's process for the determination of 

 alkalies, but the total amount of alkali probably did not exceed one- 

 tenth of one per cent of the mineral. The mineral, dried at 100°, 

 lost upon ignition, 



(!•) (2.) (3.) (Mean.) 



11.65 11.67 11.71 11.68 



per cent of its weight. The details of these determinations will be 

 referred to hereafter. Taking, then, 11.68 as the percentage of water 

 in the mineral, the results of analysis are as follows : — 



(1-) (2.) (3.) (Mean.) Ratio. 



Si 38.17 37.93 38.00 38.03 .... 2.54 



M 12.84 13.07 12.87 12.93 75 



^e 7.02 7.02 7.02 7.02 26 



i'e .50 .50 .50 .50 01 



^% _ 29.72 29.57 29.64 .... 1.48 



ii, E .... trace 



H 11.68 11.68 11.68 .... 1.30 



99.92 99.64 99.80 



The second of these two varieties of vermiculite occurs at Pelham, 

 Mass. It has a greenish-yellow tint, resembling closely in color the 

 Culsagee variety. In the specimen examined, however, the scales 

 were very much smaller than those of the Culsagee variety, and exhib- 

 ited no regular outline. Examined with the microscope, they ap- 

 peared equally free from interpenetrating material. The plates do not 

 show the striation observed both in Culsageeite and Jefferisite. No 

 evidence of macling could be found. The plates were optically biaxial, 



