January 5, 1905] 



NA TURE 



233 



when the instrument is out of action the tube lies hori- 

 zontally, and the mercury lies on one side of the cistern, 

 leaving the open end of the tube exposed to the air. When 

 the tube is brought into a vertical position the mercury 

 flows over and closes the mouth of the tube, and then 

 flows down the tube to a greater or less depth, dependent 

 upon the atmospheric pressure at the time. We have made 

 a number of comparisons with a mercurial standard baro- 

 meter, and find that its indications are correct to within 

 about 012 inch. The readings, to the nearest tenth of an 

 inch, or, by interpolation, to the hundredth of an inch, 

 can be rapidly obtained. As a weather-glass it appears to 

 be very useful' and even less likely to get out of order 

 than an aneroid, but it would not be suitable for accurate 

 scientific observations like an ordinary mercurial barometer. 

 It has the advantage of being less costly, small in size, and 

 easier of transport than an ordinary barometer. 



We have received from Messrs. C. F. Adolph and Co., 

 of 14 Farringdon Road, E.C., their new price list of 

 selenium cells and apparatus. This firm has introduced a 

 new type of selenium cell which possesses the advantage 

 over the old form of cell that it is exposed to the light on 

 two surfaces with a consequent increase in the sensibility 

 of fully 75 per cent. Complete sets of apparatus for 

 demonstrating the sensitiveness of selenium to light and 

 the transmission of sound by means of light are also 

 described and illustrated in the list. 



In No. 21 of the Physikalische Zeitschrift Mr. Josef 

 Rosenthal describes a number of improvements which he 

 has introduced in the construction of mercury air-pumps of 

 the Sprengel type. These pumps usually suffer from the 

 disadvantage that the glass tube in which the mercury falls 

 is liable to sudden fracture after the pump has been in action 

 during a few weeks. The fracture appears to be due to the 

 friction of the mercury on the glass producing an electrical 

 charge which, by influencing the moist air without, con- 

 verts the glass wall of the tube into the insulator of a 

 condenser. The possibility of a discharge through the glass 

 is eliminated by surrounding the dropping tube with a larger 

 glass tube filled with oil, which acts as an efficient in- 

 sulator. It is stated that a tube protected in this way lasted 

 five months, although in daily use. 



The American Journal of Science for November, 1904, 

 contains an investigation by Mr. Bertram B. Boltwood of 

 the radio-activity of natural waters which is of particular 

 interest because of an attempt that is made to explain its 

 origin. It is shown that neither hot nor cold water dis- 

 solves any appreciable quantity of radium, as such, from a 

 mass of finely powdered uranium minerals consisting 

 principally of uranophane, although a brief contact with 

 these minerals is sufficient to impart to water enough of 

 the radium emanation to produce a very marked radio- 

 activity. Water can also acquire a measurable quantity of 

 the radium emanation by simple contact with gaseous 

 mixtures which contain it. It is considered that an 

 extremely minute trace of uranium minerals in the rocks 

 and soils through which a water percolates would be 

 sufficient to impart to it a measurable radio-activity. But 

 waters such as those of Bath and Baden Baden, which con- 

 tain true dissolved radium, must owe the presence of the 

 latter to a special decomposition taking place under the 

 influence of high temperature and great pressure. 



Messrs. Longmans and Co. have in the press a trans- 

 lation, by Mr. J. Garcin, of M. Blondlot's papers on ti-rays 

 communicated to the Paris Academy of Sciences. The 

 volume will contain additional notes and instructions for 

 the construction of phosphorescent screens. 

 NO. 1836, VOL. 71] 



Messrs. Macmillan and Co., Ltd., have published an 

 edition of " An Elementary Course of Mathematics," by 

 Messrs. H. S. Hall and F. H. Stevens, in which parts i. 

 and ii. of the authors' " School Geometry " have been 

 substituted for the parts of Euclid's elements contained in 

 previous editions. 



Messrs. F. Vieweg and Son, Brunswick, have issued 

 the fifth edition of Wiedemann and Ebert's comprehensive 

 work on practical physics — " Physikalisches Praktikum." 

 The book contains a good systematic course of practical 

 work in physics, the experiments being well arranged and 

 clearly illustrated. 



The issue of the Antiquary for January commences the 

 first volume of a new and enlarged series. The magazine, 

 which is devoted to the study of the past, has been enlarged 

 by the addition of eight pages. A new section, called " At 

 the Sign of the Owl," has been introduced, and consists of 

 about two pages of notes concerning books of archaeological 

 interest. A good selection of articles is promised for the 

 present year. 



There has now been published at the Patent Office a 

 subject list of works on the fine and graphic arts (including 

 photography), and art industries, in the library of the 

 Patent Office. The list consists of two parts — a general 

 alphabet of subject headings, with entries in chronological 

 order of the works arranged under these headings, and a 

 key, or summary, to these headings shown in class order. 

 The catalogue includes some 2916 works, representing 5373 

 volumes. 



OUR ASTRONOMICAL COLUMN. 



Another New Comet (1904 e). — A telegram from the 

 Kiel Centralstelle announces the discovery of a new comet 

 by M. Borrelly at Marseilles on December 29, 1904. The 

 position of the object at gh. 7m. (Marseilles M.T.) was 



R.A. = ih. 13m. 40s., dec. = — 10° o', 

 and its apparent daily movement was found to be -|-ibm. 

 in R.A. and —54' in declination. A nucleus was seen. 



A further telegram states that the comet was observed 

 bv Dr. Cohn at Konigsberg on December 31 at 6h. 22-2m. 

 (konigsberg M.T.), when its position was as follows : — 

 R.A. = ih. 15m. S6-S3S., dec. = -8° 29' 59". 



The position of the comet is near to that of 9 Ceti. 



Comet 1904 d (Giacobini). — Further observations of 

 comet 1904 d are published in No. 3986 of the Astronomische 

 Nachrichten, together with Herr Ebell's elements and 

 ephemeris. A photograph taken at the Konigstuhl Observ- 

 atory, Heidelberg, on December igd. I7h. 37 3m. (Konigs- 

 tuhl M.T.) showed a short tail and a complex nucleus, 

 whilst the position of the object for 19040 was 

 R.A. (app.) = i6h. 19m. 38-8s., dec. (app.) = -l-28'' 23' 9". 



Observations of Leonids .at Harvard, 1904. — Several 

 observers at Harvard kept the eastern part of the sky under 

 observation for meteors from i2h. to i7h. on the night of 

 November 14-15. As a rule, four observers kept watch, 

 whilst a fifth wrote down their results, and between them 

 they saw 275 meteors, of which 183 were Leonids. 



The foUovving table shows the horary rate, for a single 

 observer, at intervals of twenty minutes : — 



Nov. 14-15 Rate Nov. 14-15 Rate Nov. 14-15 Rale 



h. m. b, m. _ h. m. 



14 40 ... 40 



15 o .. 36 



15 20 ... 29 



Of the total number 35 were of the first magnitude or 

 brighter, but none exceeded magnitude -20. At the 

 moment of explosion the heads were generally blue or white, 

 but in two cases, at least, the colour was clearly red or 



