526 



NATURE 



[September 19, 1907 



■ ven stations) was 72-4 inches, as compareJ with the 

 i'Vcrage, 79-5 inches. Notice is directed to an apparent 

 ronnection between droughts in Natal and Mauritius, well- 

 marked winter droughts at the coast stations of the former 

 place being followed by summer droughts in Mauritius 

 at intervals of from three to seven months. 



We have received from the Deutsche .Seewarte its 

 monthly meteorological chart for the North .Atlantic Ocean 

 for September, which, like the corresponding chart pub- 

 lished in this country, is replete both on face and back 

 with information of value to seamen, and includes notes 

 on ice, fog, &x., brought down to the latest possible date. 

 k comparison of the face of the English and German 

 charts naturally exhibits slight differences in the results ; 

 this is unavoidable when compilation is made from data 

 received from different sources. The back of the German 

 publication contains, inter alia, charts showing the 

 weather conditions between Ushant and Gibraltar, and 

 sudden changes observed in the sea-surface temperature 

 south of the Newfoundland Bank, each chart being 

 accompanied with useful explanatory text. 



The Publications of the Japanese Earthquake Investi- 

 gation Committee, Nos. 23 and 24, are devoted to an 

 account and study of the seismograms of what is called 

 the "Great Indian Earthquake of 1905." The preface 

 states that these are issued as a systematised account of 

 the instrumental observations of the earthquake, to be 

 laid, for discussion, before the International Seismological 

 Association at its next general conference. The data 

 yielded by the seismograms are discussed with a wealth 

 of elaboration and tabulation which tends to obscure the 

 conclusions drawn ; some of these are diametrically opposed 

 to those generally held in this country, and the data on 

 which they are based seem more consistent with the view 

 that this earthquake was not so very "great," and that 

 the distant records are imperfect. The value of the series 

 of reproductions of forty-one seismograms taken at twenty- 

 nine different stations would have been increased had the 

 reproductions of Milne seismograms been less coarse in 

 texture, but even with this drawback they form a collec- 

 tion which will be extremely useful to students of 

 seismology, and we have only to regret that it should 

 have been left to the Japanese Government to produce an 

 adequate report of a British earthquake. 



A NEW microphone for wireless telephony, the invention 

 of Prof. Majorana, is described in the Electrician of 

 August 30. The microphone consists of a jet of water 

 Tailing on a collector made of two cylindrical pieces of 

 platinum. The two pieces of platinum are connected to 

 a battery, and a current passes depending on the thickness 

 of the water film connecting the two surfaces ; this thick- 

 ness is varied by passing the stream of water before it 

 falls on the collector through a receptacle, one side of 

 which is formed by a membrane actuated in the ordinary 

 manner of a telephone transmitter. It is stated that the 

 vibrations produce corresponding fluctuations in the w ter 

 jet, and the secondary current reproduces in consequence 

 the sound waves. The collector circuit is connected to 

 the spark-gap in the wireless transmitter, a Poulsen arc 

 In nitrogen being the most suitable spark-gap to employ. 

 No particulars are given of distances over which trans- 

 -nission has been accomplished. 



Tme Halhmonatliches Literaturverzeichnis of the Fort- 

 schritle der Physik continues to fulfil its function of bring- 

 ing the titles of papers published in the various depart- 

 ments of physics promptly before its readers. It is 

 interesting to notice that nearly 40 per cent, of the papers 

 published fall within the section cosmical physics. 

 NO. 1977, VOL. 76] 



The general characteristics of the treatment of 

 elementary geometry adopted by Messrs. Barnard and 

 Child in their " New Geometry for Schools " (Messrs. 

 Macmillan and Co., Lid.) and similar volumes have been 

 described in these columns on more than one occasion 

 (vol. Ixix., pp. 97 and 391 ; vol. Ixxi., p. 174). To meet 

 the requirements of teachers and students who wish only 

 to follow the subject up to particular standards, the course 

 of work has been subdivided, and three new volumes con- 

 taining various sections have recently been published. 

 Part iii. of " A New Geometry " contains the equivalent 

 Euclid, Books ii., iii. (35-7), and the harder parts of 

 Book iv. ; parts iii. and iv. (in one volume) include, in 

 addition, Euclid, Book vi., and the algebraical treatment 

 of ratio and proportion for commensurable quantities ; and 

 " A New Geometry for Middle Forms " contains the sub- 

 stance of Euclid, Books i.-iv., together with additional 

 matter. The six volumes, which now form Messrs. 

 Barnard and Child's series on practical and theoretical 

 geometry for schools, provide students in any part of the 

 Empire with courses of study which cover satisfactorily 

 the revised syllabuses of examining bodies, and follow the 

 reformed methods of geometrical teaching brought about 

 by the reports of committees of the British Association 

 and the Mathematical Association. 



OUR ASTRONOMICAL COLUMN. 



Daniel's Comet (igo7<J). — An excellent reproduction 

 from a photograph, and a description of comet igoyd, are 

 published in the September number (p. 385) of the BulUtin 

 de la Sociili astroiwmique de France by M. F. Qu^nisset, 

 of the Juvisy Observatory. With a clear sky, the comet 

 appeared incomparably brighter than the Andromeda 

 nebula, and gave the impression of being about the bright- 

 ness of a second-magnitude star ; the tail could be seen, 

 by the naked eye, extending to a distance of 8° or 10°. 

 Between July 12 and August 15 twenty-six photographs 

 were obtained, three portrait lenses of i6-o, 13-5, and 

 3-8 cm. aperture, and 0740, 0-565, and 0.130 metre 

 focal length, respectively, being chiefly employed. On 

 these photographs the structure of the tail is very sharply 

 defined, and on one obtained with the last-named objective 

 the tail can be traced for not less than 17°. From the 

 photographs obtained with this instrument on August ~ 

 and 8 there is evidence of a rotatory motion of the comet 

 about a line joining the nucleus and the sun. 



As seen in the 24-cm. (lo-inch) equatorial and on the 

 photographs taken with a Viennet objective, the structure 

 of the tail near the head was fan-like, the colour being 

 a fine green, and the brightest part was directed towards 

 the sun. A visual examination of the comet with a 

 spectroscope revealed the three strong hydrocarbon bands 

 on a brilliant background of continuous spectrun). These 

 bands were sharply defined on the red side, and faded 

 away gently towards the violet, and, on replacing the 

 spectroscope slit, they, with others, were seen resolved 

 into lines ; the order of their brightness was green, blue, 

 orange. 



From Mr. G. Gillman, of Aguilas (Spain), we have 

 received a drawing showing the observed path of the comet 

 from August 13 to 21. On the former date Mr. Gillman, 

 as shown on his drawing, was able to trace the tail for a 

 distance of 25° in a W.S.W. direction. 



Owing to its decreasing brightness and to the fact that 

 it does not rise until about ij hours before sunrise, the 

 comet is becoming a difficult object, but we give below 

 a further extract from the ephemeris published in No. 4196 

 (P- 337. August 23) of the Astronomische Nachrichten : — 



Ephemeris 12ft. (Berlin M.T.). 

 1907 a (true) 5 (triie) log r log A Bright- 



Sept. 21 ... 10 46-^ ... +7 5-1 ... 9-8179 ... 0-1879 ••• 6-4 

 23 ... 10 557 ... +6 25-S 

 25 ... II 4-8 ... +5 47-1 ... 9-8550 .. 02085 ••• 49 



