426 Probable Infiiience of 



Prof. Hitchcock, they differ from Heulandite in the proximate 

 measurement of planes M on T about 10° (being 120° instead 

 of 130°) as determined by the measurement of three different 

 crystals with the common goniometer. It must be confessed, 

 that the comparison of one set of characters alone, without 

 some other corroborative evidence, — especially when, as in 

 the present instance, the crystals are too small to admit of 

 the accurate use of the common goniometer, does not au- 

 thorize the making of a new species. Having received a few 

 crystals of this mineral from Prof. Hitchcock, 1 also requested 

 Mr. Teschemacher to measure them. The results showed 

 the same agreement with the recorded measurements of W. 

 Phillips, and have therefore established the true nature of this 

 mineral beyond any doubt. 



I would remark that crystals, precisely like those described 

 by Prof. Hitchcock, have lately been found in gneiss on New 

 York island, and apparently in the same rock, associated with 

 phosphate of lime, at Suckasunny, New Jersey.* There can 

 be no doubt, 1 think, that the radiated or fasciculated mineral 

 accompanying these crystals is stilbite, and not a variety of 

 Lincolnite or Heulandite, as Prof. Hitchcock supposes. 



ART. XXXVII. - PROBABLE INFLUENCE OF ICEBERGS UPON DRIFT. 

 By John L. Hayes, Porlsmoulh, N. H.t 



At a time when the attention of geologists is so generally 

 directed to observing the phenomena of drift, and especially 

 when the agency of ice is deemed so important to explain 



* Among some specimens which I have lately received from Copenhagen, 

 through a distinguished friend of science, Compte de Vargas Bedemar, I 

 observed precisely the same modified crystals with those of Lincolnite, but 

 no near approach to the form of Beaumnntite. These specimens are from 

 Faroe, a region which the Count has personally examined. 



t Originally read before the Association of American Geologists and 

 Naturalists, May, 1843. 



