January 28, 1909J 



NATURE 



Z77 



Ix the U.S. Monthly Weather Review for September 

 last Prof. C. F. Marvin describes a new form of com- 

 pensated siphon barograph, consisting of three separate 

 parts, which he has invented and has found to give very 

 satisfactory results. The long and short branches of the 

 siphon are simple, straight tubes fitted into the upturned 

 branches of the bend, or U. This three-piece construction 

 enables the barometer to be filled very easily, and, when 

 once filled, it can be dismantled and transported without 

 loss of the vacuum. In the barograph illustrated in the 

 paper the changes are magnified five times by means of 

 a large and small wheel operating on the principle of the 

 wheel and axle, with a pen marking upon a drum driven 

 by clockwork in the usual way. The drum revolves once 

 in three days and two hours, moving at the rate of about 

 a quarter of an inch per hour. The instrument is provided 

 with a time-marking device consisting of an electromagnet, 

 which operates once each hour. A small section of an 

 actual record is reproduced in the paper, and shows that 

 the pen responds to minute changes of level of the mercury. 

 Prof. Marvin concludes by giving useful illustrations of 

 the various methods adopted in filling barometer tubes. 



The British Fire Prevention Committee has just pub- 

 lished two pamphlets giving particulars of experimental 

 tests which have been carried out by it of the merits 

 of asbestos cloths, sand, steam, hand-pumps, buckets of 

 water, and other appliances in common use for extinguish- 

 ing fires when they originate. The tests appear to have 

 been thorough, and they were also carried out with 

 impartiality, so that the records furnish valuable data for 

 determining which is the most suitable equipment to adopt 

 in given circumstances. 



The current number of the Zeitschrijl fiir physikalische 

 Cheiiiie (January 5) contains a contribution by E. Cohen 

 and H. R. Kruyt on the E.M.F. of the Weston cell. They 

 are unable to confirm the abnormal results for 10 per 

 cent, and 12.5 per cent, cadmium amalgams described by 

 Janet and Jouaust, but are in agreement with Bijl's views. 

 .At 0°, cells made up similarly show variations amounting 

 to 0-; millivolt, and if an accuracy of this order is re- 

 quired in comparisons at low temperatures the cells must 

 be immersed in a bath. Full details are given of the 

 precautions taken to secure the purity of the materials 

 used, and a diagram is given of a convenient form of cell. 



The notification of the Metropolitan Gas Referees for 

 the year 1909 is practically identical with that for 1908. 

 In addition to a detailed account of the construction of 

 the apparatus used, methods of testing are laid down for 

 the detection of sulphuretted hydrogen, the determination 

 of the amount of sulphur compounds (other than 

 sulphuretted hydrogen), of the illuminating power with the 

 London Argand, No. 2, and with the fiat flame, of the 

 gross and net calorific values, and of the pressure. Of 

 these, the only figures now subject to statutory require- 

 ments are the sulphuretted hydrogen, pressure, and 

 illuminating power as measured by the No. 2 London 

 .Argand. 



In a paper published in No. 4, vol. x.xviii., of the .45/1-0- 

 physical Journal, Prof. Fowler and Mr. A. Eagle describe 

 a method whereby from any prismatic spectrum a rectified 

 copy, for comparison with a grating spectrum, may be 

 obtained ; the importance of such a method will readily 

 appeal to all spectroscopists. Dr. E. S. King has 

 previously obtained such corrected copies, but, apparently, 

 he secured the necessary adjustments of his copying 

 apparatus by trial. In the method now published these 



NO. 2048, VOL. 79] 



adjustments may be calculated so that the apparatus may 

 be set up straightway, and very accurately rectified spectra 

 obtained. The writers state the formulje they have 

 developed for this purpose, and also give an example to 

 illustrate the accuracy of the results obtained. In a section 

 of the spectrum of the iron arc, extending from \ 4S23 to 

 ^ S'27, the greatest error in the result amounted to only 

 o-i of a tenth-metre; this corresponds to a displacement of 

 about 1/300 of an inch, the range of the whole spectrum 

 being more than 10 inches. 



Messrs. Isenthal and Co.'s new list of rheostats con- 

 tains illustrations and particulars of many forms and types 

 of resistances for switchboards, bridges, and experimental 

 work. A neat form of potentiometer rheostat is shown, 

 which consists of a cylindrical block of serpentine having 

 a helical groove cut on its outer surface, into which the 

 wire is placed. A central spindle is firmly fi.xed to the 

 block, and a screw-thread is cut on this spindle having 

 the same pitch as the helical groove on the block. A 

 tube fits over this spindle and carries the sliding spring 

 which makes contact. An ebonite knob fixed at the top 

 of the tube enables the sliding contact to be moved gradu- 

 ally along the whole length of the wire, and its position 

 can be read off on a scale engraved on the spindle of the 

 tube. Coarse adjustments can rapidly be made bv press- 

 ing a button on the central rod, which releases the con- 

 tact and enables it to be displaced in a vertical direction. 

 When the button is released the contact always auto- 

 matically replaces itself on the wire, and cannot fait 

 between the turns. Some good regulating resistances with 

 sliding contacts are also shown. These are made up of 

 slabs of hardened asbestos, which may be mounted up 

 together to form magazines of ten or any number of 

 slabs. The contact levers each work between two slabs, 

 making contact on both simultaneously. The contact 

 fingers are very carefully made, and ensure a more gradual 

 regulation than is usually the case in this type of resist- 

 ance. The potentiometer rheostat mentioned above is also- 

 adapted to a Wheatstone drum bridge, which is made with 

 a fixed drum and an additional direct ohm scale. Plug 

 contacts for the comparison resistances and the terminals 

 are carried on the base, and the resistances of o-i, i, 10, 

 100, 1000 ohms are enclosed in a ventilated box on which 

 the whole is mounted. Several types of electric furnaces 

 are also described. 



The first article in the February number of Travel and 

 Exploration, published by Messrs. Witherby and Co., is 

 on Dr. Sven Hedin's explorations, by Sir Thomas Holdich. 

 Among other articles in this attractive magazine is one by 

 Dr. C. G. Seligmann, on the V'eddas of Ceylon. The 

 interesting text and brilliant illustrations should make the 

 magazine appeal to a wide circle of readers. 



Science Progress for January well maintains its usual 

 high standard of interest. The articles on the destruction 

 of wood by fungi, by Dr. A. H. Reginald Buller ; the 

 south-eastern coalfield, its discovery and development, by 

 Mr. Malcolm Burr ; and the Palaeolithic races and their 

 modern representatives, by Prof. W. J. Sollas, will appeal 

 to a wider circle than the remaining more technical articles. 

 A characteristic paper by Prof. H. E. Armstrong, entitled' 

 "A Dream of Fair Hydrone : a Chemical Idyll," will be 

 read with interest by chemists. 



We have received a copy of the thirty-sixth annual issue, 

 that for 1909, of " Willing's Press Guide." It contains a 

 comprehensive index of all newspapers, magazines, reviews, 

 transactions of learned societies, in fact, of every form 

 of periodical literature published in the United Kingdom. 



