1916.] The Third Indian Science Congress. cxxi 



In the hot weather months (March — May) very high negative gradi- 

 ents are frequently recorded between 8 or 9 a.m. and 5 p.m. These are 

 due to clouds of dust raised by the westerly winds usual at this season. 

 whenever the latter exceed about 16 miles an hour. 



Utility of Desiccants in Electrostatic Measurements. — By 

 V. H. Jackson, M.A., and A. T. Mukerjee, M.A. 



During most months in the year accurate measurements with sensi- 

 tive quadrant electrometers cannot be made in India without special pre- 

 cautions, owing to the high temperature and humidity. In continuation 

 of earlier work (J.A.S.B., Vol. X, 1014) the authors find that leakage can 

 be reduced to a very low and constant amount for an indefinite period if 

 the electrometer is enclosed in a hermetically sealed metal case together 

 with all accessories, and manipulated from outside by airtight connections, 

 and if the air enclosed is kept dry by sulphuric acid which can be stirred 

 or renewed when necessary. No desiccant other than sulphuric acid ha 

 been found suitable. The effect of sodium and phosphorus pentoxide i3 

 to increase the leakage above the amount usual in ordinary moist air. 

 This appears to be due to increased ionisation caused by the chemical 

 action of moisture, as noticed by Schenck when water vapour acts on 

 yellow phosphorus (Sc. Abstracts, No. 1581, November 1915). Attempts 

 to simplify the arrangements by keeping the case and its contents 10 — 15 



above the air temperature without any drying agent gave no satisfactory 

 result. 



Geology Section . 



Notes on some fish teeth from the Tertiary beds of Western 



India. — By H. C. Das-Gupta. 



In this paper the author described some fish teeth obtained from 

 the Tertiary beds of Kathiawar and Sind. Of these species one is new 

 and it has been described as Oxyrhina Feddeni. 



On the Hypersthenization of Monoclinic Pyroxenes.- By 



Kiban K. Sen Gupta. 



The alteration of hypersthene into garnet in the rocks of the char- 

 nockite series has been proved by Sir Thomas Holland, but later investiga- 

 tions point to the conclusion that hypersthene is also an alteration pro- 

 duct of augite — a monoclinic pyroxene. In some specimens it seems as if 

 the garnet has altered peripherally into a micropegmatite of pyroxene and 

 felspar. Kelyphite rims round garnets are examples of the breaking 

 down of garnets into other minerals, such as pyroxene, at least in some 

 cases. If the change is in the direction as indicated above it is to be ex- 

 plained according to Dr. Fermor as due to a release of pressure. But the 

 innumerable other instances go to show that the change is in the direction 

 from augite to garnet and not vice versa. 



Hypersthene is the most characteristic, though not an invariable con- 

 stituent. Some charnockites are entirely free from hypersthene which is 

 rather striking but not surprising in view of the supposition that both 

 hypersthene and garnet are believed to be derived from augite. This 

 granted, one or other of the ferro-magnesian minerals, such as augite, 

 garnet, hypersthene, and secondary hornblende may be found missing in 

 some rocks of the charnockite series. Although hypersthene is a charac- 

 teristic constituent of the charnockites of South India as elsewhere, the 

 green augite is the fundamental constituent. The bluish green colour of 

 the rays vibrating parallel to the minimum axis of elasticity r in the 

 augite is similar to that of the rays vibrating parallel to the corresponding 



