632 



NATURE 



[July 14, 192 1 



In the latest issue of the Transactions and Proceedings 

 of the Perthshire Society of Natural Science ^vol. vii., 

 part 2, 1919-20) Mr. Henry Coates describes fully all 

 the data regarding the occurrence of the metecwitic 

 fall in December, 19 17, and the paper contains appen- 

 dices regarding the fall of 1830, records of distances 

 contained in tabulated form, and a report by Mr. 

 W. F. Denning on the path of the meteor. The 

 author has added eleven illustrations from photo- 

 graphs taken at the time and some diagrams. This 

 part of the number also contai.is a short paper on 

 the occurrence of the horned pond-weed (Zannichellia 

 pcdustris, Linn.) in Keltie Loch, near Dunning, by Mr. 

 J. R. Matthews. 



According to an article in La Nature for June 25, 

 the French Navy, during the recovery of materials 

 from many of the vessels sunk during the war, has 

 greatly improved the oxy-acetylene torch of Picard so 

 that it can be used under water. The addition which 

 has rendered this possible is a small bell-shaped vessel 

 surrounding the oxy-acetylene flame, which is kept 

 supplied with compressed air. After the flame is alight 

 and the stream of compressed air established the 

 torch may be plunged into water without being extin- 

 guished. If by any accident it was extinguished, it 

 was necessary for the diver to ascend to the air to light 

 it again. Under the auspices of the French Depart- 

 ment of Scientific and Industrial Research, M. Come 

 has recently made a further addition to the torch 

 which makes it unnecessary to ascend to relight it. A 

 tube containing an alkaline metal and an oxidiser is 

 attached to the torch and can be moved to the mouth 

 of the bell. On removing the cap from the end of 

 the tube the chemical action of the water on the mix- 

 ture produces a flame which relights the torch. The 

 addition has greatly increased the number of under- 

 water uses to which the torch can be put. 



The Journal of the Washington Academy of 

 Sciences for April 4 contains two communications 

 which deal with the steps taken by the United States 

 to acquire a better knowledge of the properties and 

 behaviour of the oceans which wash its shores. 

 Under the auspices of the National Research Council 

 a conference of representatives of the nations around 

 the Pacific Ocean was held in Honolulu in August, 

 1920, to consider what knowledge with regard to 

 that ocean was available and in what directions there 

 was most urgent need of its extension. As a result, 

 it is expected that during the present year several 

 volumes dealing with the scientific exploration of the 

 Pacific will be published. The opportunity afforded 

 by the Ice Patrol of the Atlantic in 1920 was utilised 

 by Mr. A. L. Thuras, of the Bureau of Standards, 

 to test the trustworthiness of the method of deter- 

 mining the salinity of sea-water on board ship by 

 measuring its electrical conductivity. It was found 

 both trustworthy and convenient, and it is proposed 

 to set up a self-recording apparatus based on the 

 method which will give the temperature, density, and 

 salinity of the water. 



In a paper read to the Physical Society on June 24 

 Mr. S. Butterworth discusses the errors due to 

 capacity and eddy-current effects in inductometers. 

 NO. 2698, VOL. 107] 



At low frequencies these errors are negligible, but 

 at telephonic frequencies they have to be considered, 

 and in radio-telegraphy ihe corrections which have to- 

 be applied are of the same order as the quantities 

 measured. Making the assumption that the capacity 

 effects in two coils having one end in common can' 

 be represented by two condensers shunting each coil 

 and by another condenser joining their free ends, the 

 author obtains formulae which are in good agreement 

 with experiment. When the secondary e.m.f. induced 

 in a secondary circuit is in exact quadrature with the 

 current in the primary the mutual inductance is 

 "pure." This assumption is made in the proof of 

 the Heaviside and Carey-Foster inductance bridges. 

 The author works out the theory of these bridges ork 

 the assumption that the mutual inductance is not 

 pure, but varies with the frequency. Experimental 

 verifications of the theory are given. 



In the Journal of the Franklin Institute for May 

 last L. W. Austin describes experiments made to 

 determine the directions from which the atmospheric 

 disturbances noticed in radio-telegraphy appear tO' 

 come. The main observations were made in the West 

 Indies, California, and Washington. The author con- 

 cludes that on the Atlantic coast of the United States^ 

 the disturbances come e.ither from the direction of 

 Mexico or from that of the Allegheny Mountains. On 

 the Pacific coast the disturbances are much weaker 

 and their direction is more variable. They seem to come 

 from centres at much shorter distances, and generally 

 in the direction of mountains. At Bremerton and Astoria 

 most of the disturbances come from the direction of 

 Mount Ranier, a lofty and isolated peak. In Porto 

 Rico the disturbances were mainly of local origin and 

 very diffuse. When they came from the sea there was 

 generally land at no great distance in that direction. 

 When the disturbances increase with increase of wave- 

 length, as at Washington, they come from distant 

 origins ; when they vary little with wave-length, as at 

 San Francisco and San Diego, the focus of the dis- 

 turbance is near at hand. The origin of the disturb- 

 ances seems to be in the upper atmosphere, probably 

 between masses of air at different potentials. The 

 results obtained indicate that a world-survey of these 

 "static " disturbances would lead to important results. 



In electroculture it is customary for the high 

 potential wires to be placed horizontally and parallel 

 to one another above the growing crop. As the 

 number of wires 'is limited the question arises as to 

 how far the electric force at the ground level is 

 uniform. In a paper to the Physical Society read 

 on June 24 Dr. Chree gives simple formulas show- 

 ing how the potential gradient at the surface of zero 

 potential (generally the ground level) depends on the 

 height and spacing of the wires. These formulae will 

 be of use in practical work. It is probable that a 

 high potential gradient is injurious, and a low 

 potential gradient beneficial in certain cases. It is 

 important therefore to obtain uniformity of conditions, 

 for this should at least make it easier to draw con- 

 clusions as to the merits of electroculture. An imme- 

 diately useful deduction from the author's formulae 

 is that a very uniform set of conditions can be secured 



