October 31, 1895] 



NA TURE 



65: 



« 



In a lecture recently delivered by Dr. W. J. van Bebber, at 

 Lubeck, and printed in the Atinalen der Hydrographie iiitd 

 Maritimcn Meteorologit: for September, he discusses the possible 

 means of improving storm-warning signals. As Dr. v. Bebber 

 has charge of the weather service at the Deutsche Seewarte, his 

 news on the subject carry considerable weight. He points out 

 that notwithstanding constant exertions to place weather pre- 

 diction on a sound and trustworthy basis, the solution of the 

 question remains in a somewhat unsatisfactory condition. He 

 makes the following suggestions for the furtherance of the 

 object in view, most, if not all, of which have already been 

 discussed at various mereorological conferences, and have fallen 

 through on the score of expense or other hitherto insuperable 

 diftlculty : — (i) Extension of telegraphic communication west- 

 ward (Faroe, South CIreenland, iSrc. ). This proposal was 

 advocated by the late Captain Hoffmeyer. (2) Acceleration of 

 exchange of telegrams, by the introduction of the "circuit- 

 system." By this means the telegrams in America are received, 

 and warning messages despatched within two hours of the time 

 of taking observations. (3) More frequent information, by 

 means of telemeteorography, or the connection of self-recording 

 instruments with central offices. The practicability of this 

 method has been put to test in the Netherlands, and the subject 

 was recently discussed by the International Meteorological 

 Committee at Upsala. (4) Exchange of telegrams between 

 neighbouring signal stations ; this plan has been found to work 

 successfully in Germany and America, and by its means more 

 recent information is obtained by the seafaring community 

 as to the sudden approach of stormy weather. (5) The 

 popularisation of weather knowledge among the public by 

 means of weather charts, and (6) the preparation of 

 an atlas of types of weather. The number of charts 

 required would be at least 500 or 600. This suliject lias been 

 suggested by Mr. .\bercromby antl others. 



■ A NEW method of measuring the resistance of an air-gap 

 during the passage of a spark has been devised by M. Victor 

 Biernacki, and is described in the current number oi \.\\e Joiinii!/ 

 clc Physique. In the case of a Hertzian resonator in unison 

 with an exciter, the forced vibrations and the natural vibrations 

 of the resonator (the presence of which, according to Poincarc 

 and Bjerkncss, explain multiple resonance) have the same 

 periodic time, and according to Bjerkness's theory these two 

 vibrations are in oppose phase. In order that these two vibra- 

 tions may entirely destroy each other, it is necessary that they 

 l)e equally damped — that is to say, that the resistance of the 

 exciter and resonator should be equal. The author has verified 

 this consequence of the real presence of these two sets of vibra- 

 tions in the resonator, by steadily increasing the resistance of the 

 resonator, starting with a resistance less than that of the exciter. 

 In this way he has succeeded in entirely destroying the vibra- 

 tions in the resonator, and according to theory at this 

 moment the resistances of the exciter and resonator must be 

 I qual. Since these had the same dimensions, and were made 

 "f the same material, but the spark-gap in the exciter was re- 

 placed by a litjuid resistance R, it follows that the value of R, 

 which corresponds to the completed extinction of all vibrations 

 iu the resonator, is equal to the resistance of the spark-gap in 

 the exciter. The resistance R consists of a glass tube filled 

 with a solution of copper sulphate of various strengths. .V 

 Geissler tube or a bolometer is employed to indicate the pre- 

 sence of the viljrations in the resonator. As the dilution of the 

 sulphate of copper solution is increased, the vibrations in the 

 resonator decrease in intensity. These die out, and on further 

 dilution reappear. For a spark-gap of I cm. the resistance R 

 v.iricd between 300 and 800 C.G.S. units. With a spark-gap 

 0'4 m.m. long, however, the resistance is found to be between 

 1200 and 1500 C.G.S. units. This increase of the resistance as 



NO. 1357, VOL 52] 



the spark diminishes is very curious ; but it is important to notice 

 that the decrease in the length of the spark is accompanied by 

 a change in other properties of the spark. When the terminals 

 of the spark-gap are near together it is very difficult to obtain a 

 straight and while spark, the spark generally being slightly 

 violet in colour and ramified in appearance. With a longer 

 spark-gap, however, it is much easier to obtain a spark which 

 is white in colour and nonraniifie<l, and which passes with a 

 sharp noise. It is a spark of this latter character which HerU 

 found to be best suited to his classical experiments, and the fact 

 established by the author that such a spark really offers less 

 resistance than a short violet spark, affords an explanation of 

 Hertz's observation. 



With the title " The People's Stonehenge," a slim little 

 pamphlet, by Mr. J.J.Cole, has been published by Mr. J.Doney. 

 Sutton, Surrey. The [jamphlct contains ten repro<luctions from 

 photographs of the objects at Stonehenge ; and these, with the 

 short descriptive text which accompanies them, brings out the 

 points of interest in the most wonderful of our archaeological 

 remains. 



AsTRO.NOMERS should be grateful to Messrs. W. Wesley and 

 Son for the excellent catalogue of works on astronomy just 

 published as No. 124 of the Natural History and Scientific 

 Book Circular. The classification is very elaborate, the books 

 being arranged under no less than twenty-four headings. In 

 each section the books follow the alphabetical order of authors' 

 names. Both the arrangement of the sections and the divisions 

 adopted are admirable, and reflect great credit upon the 

 compilers. Bibliophiles well know that a bookseller's catalogue 

 is a mine of information, and they will be joined by astronomers 

 in appreciation of the efforts of Messrs. Wesley and Son to 

 produce a full and accurate list of works on celestial science. 



The Proceedings of the American Philosophical Society for 

 January, 1895, reached us at the beginning of this week. Among 

 other papers contained in it we notice a description (with four 

 plates) of an old " Horologium Achaz," or Dial of Achaz, by 

 Mr. J. F. Sachse ; a pajier on " The Significance of the Jugal 

 Arch," by Mr. D. D. Slade ; a note proving that thin leaves of 

 gold, similar to those exhibited by Mr. J. W. Swan at the Royal 

 Society in June 1894, were produced by Mr. A. E. Outerbridge 

 seventeen years ago (on this matter, see Mr. Outerbridge's 

 claim for priority in Nature, vol. li. p. 608, 1895) ; a paper by 

 Dr. D. G. Brinton on the " Protohistoric Ethnography of 

 Western Asia," and the " Fourth Contribution to the Marine 

 Fauna of the Miocene Period of the United States,' by Prof. 

 E. D. Cope. 



Messrs. M.vcmillan have just issued the first part of the 

 " History of Mankind," by F. Rat/.el, in which the learned 

 author states what the task of ethnography is, and describes the 

 situation, aspect, and numbers of the human race, together with 

 a series of preliminary observations on the rise and spread of 

 civilisation, religion, language, &e. Where possible he illustrates 

 his remarks by pictures of genuine "savage" remains, and hi* 

 theories have usually a good substratum of fact. It is, of 

 course, too early to pass a final opinion on the work ; but we 

 believe that it supplies a want among the increasing number of 

 people who need a popular history of the beginnings of the 

 human race, and an intelligible account of the conditions under 

 which our primitive ancestors lived. The part before us is 

 printed in good type on excellent paper, and contains a coloured 

 plate of a Bosjesman family, and a map of North and South 

 America, besides several illustrations scattered throughout the 

 text. 



Dr. a. B. Meyer has sent us a memoir (Abh. 11. tier, des K. 

 Zoolog. II. .Anlhropol. Etiiii. Museums zu Dresden 1894-95) on a 



