OF ARTS AND SCIENCES. 



5T 



Si 



f 37.58 

 20.04 



(1) 



Al Fe 



19.73 5.95 



9.19 1.78 



Fe Mg 



a58 25.13 

 0.14 10.05 



ft 



11.09 = 100.06 

 9.86 



(2) 



(3) 



= 100.38 



= 100.01 



19.79 

 2. 



11.20 

 1.13 



10.17 

 1.03 



9.86 

 1. 



has published two analyses of the Culsagee vermiculite, made in his laboratory 

 by Mr. Chatard and Dr. Koenig. Their results agree very closely with those 

 given above, except in the amount of water ; and since, as Dr. Genth states, the 

 analyses were made with material which had been dried in vacuo over sulphuric 

 acid for only four days, it is obvious that they have estimated as combined 

 water a large portion of wliat we, for reasons stated, have regarded as hygro- 

 scopic moisture. Reducing their results to the same standard as our own, 

 the close agreement becomes evident. We give, for comparison, first the 

 results, as published ; second, the same reduced to a water percentage of 11%; 

 third, the corresponding oxygen or atomic ratios. 



P 



< 

 ts 

 O 



O 



K 



ft 



aoo.18 



: 100.22 



The close agreement of these results with our own, obtained by different 

 processes and with different specimens of the mineral, indicates a remarkable 

 constancy of composition for a micaceous mineral. I have confirmed Dr. Genth's 

 observation of tlie presence of a very small amount of nickel in the mineral, 

 and I also detected in it a trace of copper. 

 VOL. I. 8 



