Penfield and Sperry — Miner alogical Notes. 31 7 



elevation, the downward attraction of the cone is then added, 

 and this compared with the actually observed decrease gives its 

 density. 



The conclusions drawn from the observations are therefore : 



I. Deflections of the plumb-line are greater on island than 

 on continental mountains, presumably on account of the lighter 

 surrounding sea water; and gravity is not in defect because 

 it is here estimated from the true sea level and not from a sea 

 elevated by continental attraction. 



II. Deflections appear to be greater in the vicinity of ex- 

 tinct volcanoes than near active ones. 



III. The so-called "hidden causes," which in the case of 

 the Himalayas give a variation of gravity several times as 

 great as those arising from the attraction of the mountains 

 themselves, do not exist in the Hawaiian Islands. 



Aet. XXXI V. — Mineralogical Notes ; by S. L. Penfield 

 and E. S. Spekry. 



1. Beryl. 



In connection with the previous communications on the 

 chemistry of beryl from this laboratory,* we thought that it 

 would be of interest to re-examine one of the beryls containing 

 the most alkali to prove if possible the correctnels of the as- 

 sumption which we had made, that the alkalies when present 

 replace the beryllium. For this purpose we selected the cae- 

 sium beryl from Norway, Maine, which had been previously 

 analyzed and described in one of our former papers, and sub- 

 jected it to a very careful chemical analysis by Mr. Sperry, 

 with results which are given below. We also publish the 

 chemical analysis of a transparent yellow beryl, known by some 

 as golden beryl, from Litchfield Co., Ct., which is collected and 

 used as gem material. The mineral was perfectly pure and 

 was sent to us by Mr. Geo. F. Kunz, of New York. A third 

 beryl which we have investigated is a transparent glassy vari- 

 ety from Willimantie, Ct., with very unusual crystalline habit, 

 which was brought to our notice by Mr. H. N. Bill, of Willi- 

 mantic, Ct., who collected it from a narrow vein of coarse 

 granite, at an excavation for a roadway on Oak street, a short 

 distance north of the residence of Mr. Joel Fox. The speci- 

 men is irregular in shape, not over 2^ inches in its greatest 

 diameter, it is clear and glassy though much cracked and soiled 

 by infiltrating clay, and with the exception of a small part, 



* This Journal, III, xxviii, 25, and III, xxxii, 110. 



