Ixvii 



variety, and No. 3, a pseudomorph afterwood. The results of 

 an analysis gave 



No. I. Nn. 2. No. 3. 



Moisture 5.58 4.37 2.61 



Lost by ignition 7.77 8.50 13-676 



Silica 82.66 S3. 89 81.94 



Iron and Alumina 2.28 2.27 1.12 



Lime 1.128 0.318 0.41 



Magnesia trace trace trace 



Alkalies 0.364 0.514 0.244 



Sulphuric Acid trace trace trace 



99.782 99.862 100.00 

 A combustion analysis shows that 3.38 percent, of the 13.676 

 per cent, loss by ignition in the pseudomorph is carbon. Calcu- 

 lating from the general formula for wood 



(C, 4y.j ; H, 6.3; 0,44.6), 

 we have 6.88 per cent, of wood remaing in this specimen. 



By way of comparison the following analyses of Geyse rite from 

 other localities were submitted : 



Iceland, New Zealand, 

 by Forchhammer. by Mallet. 



Silica 84.43 94.20 



Alumina 3.07 i .58 



Ferric Oxide 1.91 0.17 



Lime 0.70 trace 



Sodium Chloride , 0.85 



Water 7.88 3.06 



Alkalies 0.92 



Magnesia i .06 



99.97 99.86 



Mr. Pritchett presented a paper entitled " Ephemeris of the 



Satellites of Mars for the Opposition of 1881." 



Chas. Ludeking was elected associate member, and George C. 



Pratt was elected corresponding member. 



December 5, 188 1. 



Dr. Engelmann in the chair. Nineteen members present. 

 Geo. W. Lettermann,of Allenton, presented specimens of tree- 

 trunks of woods from Arkansas. The specimens were Xantho- 



