November 18, 1922] 



NA TURE 



66s 



hence the number of molecules with an orbit (n, n') 

 at any instant rapidly decreases with the increase of 

 n and n'. If we assume that the hydrogen gas con- 

 tains only the first and second kinds of molecules, 

 viz., 35 and 65 per cent, respectively, then the 

 calculated value exactly coincides with that observed. 

 K3taro Honda. 

 Research Institute for Iron, Steel, 

 and other. Metals, 

 Imperial University, Sendai, Japan, 

 September 22. 



Gravity Observations in India. 



The importance of the bearing of a change in the 

 force of gravity, if such could be established, on 

 all problems connected with the physics of the earth, 

 especially those of the origin of mountains, continents, 

 and oceans, is sufficient justification for directing 

 attention to certain peculiarities in the determina- 

 tions which have been made at Dehra Dun. 



When observations of gravity in India were 

 resumed in 1904, with a group of four identical half- 

 seconds pendulums of v. Sterneck's pattern, the 

 value of gravity at Dehra Dun was determined, by 

 comparison with Potsdam, as 979-063 dynes. The 

 earlier observations of Basevi had given a value 

 equivalent to 978-962 dynes, so there was an apparent 

 increase of o-ioi dyne in the interval between the 

 two sets of observations. 



A fuller examination of the evidence has shown 

 that no such conclusion can be drawn from the 

 comparison of these two sets of observations. Basevi's 

 final value at Dehra Dun was derived from an 

 elaborate series of observations, made in a room 

 specially adapted for experimenting on the effect of 

 changes of temperature, and in this the legs of the 

 stand were supported on brick pillars. At the time 

 it was unknown and unsuspected that this would 

 seriously vitiate the results, and we have also on 

 record the value obtained from a preliminary observa- 

 tion, conducted under conditions similar to those in 

 his other stations, where the stand rested directly on 

 a concrete floor at ground-level ; this preliminary 

 observation gave a value discordant from the final 

 ones, but differing from the 1904 value by about the 

 same amount as is found in other of his stations 

 which have been re-observed. The position was, 

 therefore, that there was no proof of any change of 

 the force of gravity at Dehra Dun, but equally there 

 was no disproof of such change having taken place ; 

 all that could be said was that, if any change had 

 taken place, it must have been of a much smaller 

 order of magnitude than one-tenth of a dyne. 



In the course of the new series of observations 

 further evidence came to light. The pendulums, 

 swung regularly every year at the commencement 

 and close of each field season, showed a gradual 

 decrease in the period of vibration till, in November 

 1909, the mean period had decreased by 0-0000043 

 seconds, making the apparent value of gravity 

 979-079 dynes. Since then the time of vibration 

 showed a gradual increase till in April 1913 it had 

 reached a value only 00000012 seconds less than in 

 1904. It has been suggested 1 that the increase 

 after 1909 was due to a gradual wearing of the agate 

 edges ; the suggestion is a possible one, but it leaves 

 unexplained the diminution between 1904 and 1909, 

 which was evidently due to some cause which affected 

 all four of the pendulums in about equal degree. 

 There was no change in the routine of observation 2 

 which could account for it, and the alternatives 



1 H. J. Couchman, Prof. Pap., Survey of India, No. 15, p. 2. 



2 Records, Survey oi [n Ua, \ >1. , 191 *,. p. 33. 



NO. 276S, VOL. I IO] 



seem to be a gradual molecular change in the material 

 of the pendulums, leading to change in length, or a 

 real change in the value of the force of gravity at 

 Dehra Dun. As all four pendulums were made at 

 the same time, of the same material, and, so far as 

 possible, of the same form and dimensions, the former 

 is not impossible, but the latter would equally 

 affect all four simultaneously and alike. The situa- 

 tion therefore remained as in 1904, that, so far as 

 the Indian observations are concerned, there was 

 neither proof nor disproof of an}' change in the force 

 of gravity having taken place. 



In addition to the observations of the Survey of 

 India there have been some other determinations 

 of gravity in India. In 1905 Hecker, at Jalpaiguri, 

 obtained a value which was 0-002 dyne in excess, and 

 in 1906 Alessio, at Colaba, a value of 0-004 dyne in 

 defect, of the Survey of India values, being in sub- 

 stantial agreement with the value determined at 

 Dehra Dun in January-February 1904. In 1913 

 another determination was made at Dehra Dun, by 

 Prof. Alessio, with an apparatus consisting of eight 

 pendulums prepared for the Filippi expedition to 

 Central Asia, and the value obtained, which has 

 only recently been announced, 3 was 979-079 dynes, 

 oro-oi6 dyne in excess of the standard accepted value 

 used by the Survey of India, as determined in 1904. 

 The position therefore now is that, while independent 

 direct comparisons made in the two years following 

 the commencement of the new series of observations 

 in India showed substantial agreement, a similar 

 determination made nine years later showed a 

 material difference, and this opens out the possibility 

 that part, at least, of the changes noticed at Dehra 

 Dun may have been due to a real change in the force 

 of gravity at that place. 



The difficulty of accepting such interpretation is 

 less at Dehra Dun than at many other stations, 

 for that place lies on the fringe of the Himalayas, 

 the elevation of which has been one of the latest 

 incidents in the geological history of the earth, and 

 it also lies in a region where the surface deformation, 

 established after the earthquake of April 4, 1905, 

 shows that changes are still taking place. 



It is to be hoped that when gravity observations 

 are resumed in India the matter will be looked into ; 

 in part the doubt left by these observations might 

 be cleared up by the re-observation of some of the 

 Peninsular stations, where gravity was determined 

 at the outset of the series and about 1909. For ex- 

 ample, Colaba (1904), Mysore (1908), and Jubbulpore 

 (1910) seem convenient and suitable ; a fresh 

 determination at these stations would show whether 

 there had been a change in the force of gravity as 

 compared with the reference station of Dehra Dun. 



R. D. Oldham. 



The Miraculous Draught of Fishes. 



To the several names of the Sea of Galilee, Prof. 

 Gudger, in his verv interesting letter (Nature, 

 October 28,p. 572) has thrice added "Lake of Tiberius," 

 evidently by mistake for " Lake of Tiberias." Also 

 he omits anv reference to the important paper by 

 Prof. Theod." Barrois, " Contr. a l'etude de quelques 

 lacs de Syrie " (in Rev. Biol, du Xord de la France. 

 tome vi., 1S04), which usefully summarises what is 

 known of the fauna of the lake in modern times from 

 Belon in 1553 to his own date in 1S94. The lake, it 

 appears, contains twenty-two species of fish, some 

 small fishes and some large ones in vast abundance. 

 As of old, it is subject to sudden squalls, dangerous 

 to navigation. Some of its inflowing waters for their 



' Rilisln Man'liima, Mr,rch :9:2, Supplement, p. 73. 



