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seems more than likely too, that some of the deep furrows 
existing in rocks composed of layers of different hardness, 
may have been produced partly at least by the agency of sand. 
I greatly regret that though I continued my experiments up 
to the moment of closing the building the last night of the 
Fair, that I was not able to carry them out as I first intended. 
The specimens exhibited, however, show that sand whirled 
by the wind even at a moderate velocity, is a much more 
powerful agent than we have generally supposed, and that at 
the velocity of a whirlwind even the hardest rocks will be 
worn away with very great rapidity. 
Pror. H. Wurtz said he desired to rectify a misunder- 
standing that had occurred, in connection with his communi- 
cations to the Lyceum, on the subject of the Feldspathic 
composition that he had observed in the beds of the so-called 
“ Sandstone,” used for building-stone, from the Palisade Range 
in New Jersey. Some analysis, altogether confirmatory of 
his observations, have been published by Dr. Schweitzer, in 
the American Chemist, for July, 1871, under the title of “ The 
Felsites of the Palisade Range.” 
The use by Dr. 8., of the name Felsite, had been due to an 
incorrect apprehension of the words of Prof. W.; this term 
applying more usually to compact Feldspathic rocks of 
porphyritic or porphyroid types. Prof Wurtz had suggested 
provisionally the term Felspathites. 
November 18th, 1871. 
The President in the chair. Thirty-three persons present. 
Pror. A. M. Epwarps presented the following resolution: 
Resolved,—That the Lyceum of Natural History in the 
City of New York, has learned, with sincere grief, of the 
misfortune that has befallen its sister society, The Chicago 
Academy of Sciences, by the burning of its building, col- 
