136 Prof. J. P. Cooke and Mr. F. A. Gooch on two 



Heated in a closed tube it gives off water acid in reaction, changes 

 colour, and doubles its volume. Heated before the blowpipe 

 it fuses to a dirty enamel. 



The mineral was prepared for analysis by drying at 100° until 

 its weight was constant, and in this condition was easily decom- 

 posed by hydrochloric acid. The bases, after the separation of 

 silica, were converted into nitrates and separated by Devilled 

 process. The iron and alumina were weighed together as oxides, 

 and the magnesia as the pyrophosphate. The amount and con- 

 dition of the iron were determined by decomposing the mineral 

 by the process described by the writer in Sillinian's American 

 Journal, vol. xliv. p. 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 spectro- 

 scope in the residue obtained in Smith's process for the deter- 

 mination of alkalies ; but the total amount of alkali probably did 

 not exceed one tenth of 1 per cent, of the mineral. The mineral, 

 dried at 100°, lost upon ignition 



(1) (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 ... 



... 254 



Al . . . . 



. . 12-84 



13-07 



12-87 



12-93 ... 



... '75 



#e . . . . 



7-02 



7-02 



7-02 



7-02 . . . 



... '26 



Fe 



•50 



•50 



•50 



•50 . . . 



... -oi 



Mg .... 



.. 



29-72 



29-57 



29-64 . . . 



... 1-48 



ii, it. . . . 



.. 



trace 









H .. .. 







11-68 

 99-92 



11-68 

 99-64 



11-68 ... 

 99-80 



... 1-30 



Si : R + R : H E : R 



2-54 : 2'50 : 1'30 1-01 : 1*49 



2:2:1 2:3 



The second of these two varieties of vermiculite occurs at Pel- 

 ham, Mass. It has a greenish-yellow tint, resembling closely 

 in colour the Culsagee variety. In the specimen examined, 

 however, the scales were very much smaller than those of the 

 Culsagee variety, and exhibited no regular outline. Examined 

 with the microscope, they appeared equally free from interpene- 



