Chemistry and Physics. 199 



settled the question in favor of the theory of Lorentz. Finally, 



the weighted mean value of - - deduced by Neumann from his 



experimental data is given as 1*765 E.M.U., which agrees re- 

 markably well with the average value of the results obtained by 

 other investigators and by other sources of radiation. — Physik. 

 Zeitschr., No. 22/23, Nov., 1913, p. 1117. h. s. it. 



II. Geology and Mineralogy. 



1. Changes in Level in the Earth's Crust; by Osmond Fisher. 

 (Communicated.) — In the addendum to a paper by me, on " a 

 suggested cause of changes of level in the earth," published in 

 the March number, 1906, of this Journal (vol. xxi, p. 216), I 

 referred to a paper by Col. Burrard, Surveyor General of India, 

 published in the Transactions of the Royal Society. In that 

 paper Col. Burrard called attention to the "astonishing" differ- 

 ence of - 103 cm between the value of gravity at Dehra Dun as 

 determined by Basevi and Heaviside and that about 30 years 

 later by Capt. Lenox-Conyngham. From this difference I argued 

 that there had been a change of density beneath that station in 

 the interval. 



However, in a note to a reply to some criticisms of mine upon 

 his theory of mountains, Col. Burrard now says, that the change 

 referred to is apparent only, and was due to the vibration of the 

 brick pillars on which Basevi's pendulum was swung. 



Mr. Oldham, late of the Geological Survey of India, has now 

 examined this question, and on referring to Gen. Walker's account 

 of the "Operations" of the Survey, 1879, he finds that Basevi 

 made two sets of observations at Dehra Dun. In the first, his 

 second's pendulum was swung on a wooden support, standing on 

 a concrete floor. The result of this set of observations agrees 

 fairly well with Lenox-Conyngham's. Subsequently Basevi made 

 a second set of observations at Dehra Dun, in which his pendulum 

 was swung on brick pillars and the result obtained differed from 

 the former, and he seems to have considered the value so obtained 

 as the more trustworthy. It was to this latter result that Col. 

 Burrard referred in his paper at the Royal Society, which I 

 quoted. 



It now appears that Lenox-Conyngham, who swings his half- 

 second's pendulum on brick pillars, has found that a correction is 

 necessary to allow for the vibration of the pillars, and there can 

 be little doubt but that Basevi's second set of observations was 

 vitiated by a like cause. Consequently, as Col. Burrard now 

 says, the change of gravity, deduced by comparing Basevi's value 

 quoted with that lately obtained, is apparent only. Neverthe- 

 less, there does seem to be some reason to think that small changes 

 in the value of gravity are at present going on at Dehra Dun, as 

 reported in "Nature," in a note, vol. xci, p. 143, 1913. 



Graveley, Huntingdon, Nov. 20, 1913. 



