444 



NATURE 



[December 19, 1912 



while the sun is not eclipsed, the observation of the 

 helium (D,) line in the chromosphere by Lockyer, 

 twenty-five years before the element was discovered 

 terrestrially, and even the very recent work of Dr. 

 Nicholson in the theoretical construction of such 

 spectra as those of the unknown cosmical elements 

 nebulium and coronium. This brief enumeration will 

 serve to show that Dr. Wolf's paper is not only com- 

 prehensive, but also up to date, and should be read 

 by all interested in astrophysics. 



Elements of Recently Discovered Minor 

 Planets. — In No. 4607 of the Astronomische Nach- 

 richtcii. Dr. Cohn gives the elements and permanent 

 nuntbers of eighteen minor planets discovered during 

 iqii-i2. Four of these have been identified with 

 older discoveries to which no numbers had been 

 allotted, and eleven of the "discoveries" made during 

 i()ii have since been identified with planets previously 

 included in the official records. The total number 

 thus included, as shown by the present list, is 732. 



THE PHYSICAL SOCIETY'S EXHIBITION. 



THE eighth annual exhibition of physical ap- 

 paratus under the auspices of the Physical Society 

 of London was held on Tuesday, December 17, at the 

 Imperial College of Science, and attracted the usual 

 large attendance. At both the afternoon and evening 

 sessions a short discourse was given by Mr. S. G. 

 Brown on " Some Methods of Magnifying Feeble 

 Signalling Currents." The lecturer described several 

 instruments designed by himself for magnifying the 

 currents received through Atlantic cables, by the use 

 of which largely increased speed of signalling had been 

 made possible. The most interesting of these was one 

 in which the original signalling current moves a 

 thermo-electric junction into and out of a small flame, 

 the thermo-electric current thus produced being twenty- 

 seven times that of the signalling current. The magni- 

 fving power is approximately constant for all currents, 

 an advantage over the ordinary form of relay in which 

 the current of the local circuit is constant and is merely 

 made or broken by the signalling current. Other 

 mechanical methods of achieving the same result were 

 also described. 



Exhibits of apparatus were shown by some thirty 

 firms of manufacturers. The principal exhibit of the 

 Cambridge Scientific Instrument Co. was a complete 

 cardiograph outfit, composed of an Einthoven string 

 galvanometer, projection apparatus, camera with 

 moving plate or continuous paper for cases where long 

 records are necessary, and a switchboard by which 

 the standardisation of the galvanometer, compensation 

 for skin currents, and measurements of body resist- 

 ance could be quickly made. By an auxiliary ap- 

 paratus, records of the heart sounds could also be 

 obtained, .\nother of their exhibits was a Wilson 

 cloud apparatus for showing the path of a particles 

 or X rays bv the condensation of water upon the 

 ions. Messrs. J. J. Griffin and .Sons had an interest- 

 ing exhibition of motor-gyrostats with models for 

 illustrating the Schlick method of steadying ships, and 

 the gyrostatic mono-rail car. Mr. C. V. Boys's rainbow 

 cup for showing the colours of thin films was also 

 exhibited in action. In addition to the usual laboratory 

 instruments, Messrs. Gambrell Bros, exhibited a new 

 convection radiometer by Mr. F. W. Jordon for 

 measuring small, steady rates of evolution or ab- 

 sorption of heat. The convection current of gas pro- 

 duced by the source of heat deflects two very light 

 suspended mica vanes, the deflection being shown in 

 the usual way by a mirror. The Marconi Co. ex- 

 hibited instruments for use in wireless telegraphy. 



NO. 2251, VOL'. 90] 



including a portable knapsack receiving and trans- 

 mitting set for communicating across distances of 

 fifteen miles. The Helsby Wireless Telegraph Co. 

 showed a vibration-proof detector and a rotary 

 quenched spai'k discharger. 



Microscopes for ultra-microscopic and for metal- 

 lurgical work were exhibited by Messrs. R. and J. 

 Beck, Messrs. E. Leitz, and Messrs. Carl Zeiss. The 

 last firm also had an example of its projection 

 apparatus at work. The principal exhibits of Messrs. 

 Alexander Wright and Co. consisted of various forms 

 of Dr. Leonard Levy's apparatus for the examination 

 of mine air according to the provisions of the Coal 

 Mines Act of ign. They also exhibited some good 

 examples of palladium and platinum plating on metals 

 and gold plating on glass. 



Messrs. Kelvin and James White, Ltd., exhibited a 

 compass for use on aeroplanes. It was of the floating 

 type, and said to be entirely unaffected by the vibra- 

 tions of the engines. A Fullarton vibrometer for 

 obtaining the frequency and intensity of vibrations pro- 

 duced by any form of machinery was also shown. It 

 consists of a vibrating reed which can be adjusted 

 to the frequency of the vibration to be measured, the 

 intensity being shown by the amplitude of the vibra- 

 tion of the reed. An Aitken portable dust counter 

 for quickly estimating the number of dust particles 

 in the air, based on the method of condensation of 

 moisture on them, w-as exhibited by the same firm. 

 Mr. R. W. Paul had a large exhibit of electrical 

 measuring instruments, including several new types. 

 Among them was a string galvanometer somewhat 

 similar to the Einthoven, but with the string in a 

 horizontal position. The Irwin optiphone was shown 

 jn use. This is an instrument for magnifying the 

 motion of a vibrating body, such as the diaphragm 

 of a telephone, the wave-form of the motion being 

 obtained by the revolving mirror method. 



Messrs. A. Gallenkamp showed some cheap electric 

 furnaces and various laboratory apparatus for heat 

 experiments, including a student's optical bench for 

 radiant heat experiments. They also exhibited a 

 sensitive flame for working at the low pressure of an 

 ordinary gas supply, designed by Prof. S. P. 

 Thompson. The Westminster Engineering Co. ex- 

 hibited a small useful projection arc lamp for photo- 

 graphic work and optical lanterns. Resistance testing 

 sets were shown by Messrs. Crompton and Co., 

 Evershed and Vignoles, and Nalder Bros., and a large 

 range of switchboard instruments was exhibited by 

 the Weston Co. 



RIVERS, GLACIERS, AND THE ICE-AGE. 



BRUNO DIETRICH, of Potsdam, has made a 

 geographical study of the Moselle valley 

 (" Morphoiogie des Moselgebietes zwischen Trier und 

 Alf," Verhandl. des naturhist. Vereiiis der preuss. 

 Rheinlandc, 191 1, for 1910, p. 83). Basing his de- 

 scription on the geological structure and history of 

 the district, he shows how the valley has been cut in 

 a pre-Miocene surface of denudation. The meanders 

 that arose on this fairly even surface are now traced 

 as winding ravines (p. 120), owing to the elevation of 

 the country and the consequent lowering of the base- 

 level of the Moselle. The tributaries of the left bank, 

 however, are held to have been incapable of forming 

 such large meanders as are now seen in the forms of 

 their ravines. At present they wander somewhat aim- 

 lessly in the flat land of their floors, now cutting back 

 one valley-vvall, now the other. Their valley-flats 

 (Talauen) arc attributed to lateral erosion at a time 

 when the land remained stationary for a time (p. 130), 

 and we gather that these flats have become per- 



