December 14, 191 ij 



NATURE 



225 



mination of the ampere in absolute measure at the Bureau 

 of Standards. A current balance of the Ravieigh type was 

 used, a coil being suspended from one pan of a balance 

 so that it hung horizontally between two horizontal fixed 

 coils of double its diameter, the three coils being coaxial. 

 The change of weight in one pan of the balance necessary 

 to maintain equilibrium when the current in the fixed 

 coils was reversed was determined. The absolute value of 

 the chemical equivalent of silver obtained by means of the 

 balance is 1-11804 milligrams per coulomb. The value 

 adopted at the London Conference in 1908 was i-ii8oo. 

 The electromotive force of the Weston normal cell at 

 20° C, obtained by sending one absolute ampere through 

 an international ohm, was found to be 101822 volts. 



At the recent Karlsruhe meeting of the Naturforscher- 

 versammlung Prof, von Kowalski, of Freiburg (Switzer- 

 land), gave a summary of our present knowledge of the 

 phosphorescence of organic substances at low tempera- 

 tures, a knowledge which we owe largely to the observa- 

 tions made by him and his pupils. Many organic sub- 

 stances which exhibit no signs of phosphorescence at 

 ordinary temperatures become phosphorescent in liquid air, 

 and the intensity of the effect is increased if the substance 

 is in solution in water or in alcohol to a concentration 

 of about one-twentieth normal. Subjected to ultra-violet 

 light for an instant, the solid solution gives a continuous 

 phosphorescent spectrum, which gradually fades away, the 

 longer waves disappearing first. If the exposure to the 

 light is continued for a second or more the phosphorescent 

 spectrum shows, in addition, a number of bright bands 

 which persist longer than the continuous spectrum, and in 

 fading away appear to spread themselves over the whole 

 spectrum. These bands aie intimately connected with the 

 chemical structure and with the ordinary absorption spec- 

 trum of the substance investigated. Their positions can 

 be obtained by displacing the absorption bands through a 

 fixed interval towards the red end of the spectrum. 



Sever.al new models of microscopes, particularly the 

 type known as the " Handle Model," are described in a 

 catalogue received from Messrs. R. and J. Beck, Ltd. It 

 is a matter of no small importance to the student to be 

 able to lift his instrument without fear of straining anv 

 of its parts or of dislocating the objective in relation to 

 the object. Many cheap microscopes are so designed that 

 it is necessary when moving them to grasp the base ; other- 

 wise considerable strain is thrown on the fine adjustment. 

 The models referred to are made in different patterns to 

 suit either the student or the advanced worker, and in 

 either case the price is moderate. The cheapest of the 

 series is an example of what can be done in this country 

 when modern methods of production are adopted. It is 

 probably the least expensive microscope, for the adjust- 

 ments provided, at present to be obtained of either English 

 or Continental manufacture. The fine adjustment is of 

 the lever type, so that the chance of it getting out of 

 order or of becoming les: accurate as the result of wear 

 is reduced to a minimum. The stand is supported on a 

 foot of the horseshoe type, and the objections to this 

 design are to some extent obviated by lengthening the 

 point of support towards the observer, with the result that 

 increased stability is secured. 



Students and teachers of applied mechanics in search 

 f new examples as test exercises will find the set prepared 

 tiv Mr. C. E. Inglis (Cambridge University Press, price 

 -i. 6d. net) to be of service. There are, in all, 160 

 • xercises, divided into twenty papers; these are chiefly 

 drawn from examination papers set at the Cambridge 

 Engineering Laboratory, ancf the standard of most of the 

 NO. 2198, VOL. 88] 



problems is that of the " A " papers in the Engineering 

 Tripos examinations. Answers to the problems are 

 included, but no hints for solution are given ; hence the 

 questions fulfil the purpose of the author, which is to 

 provide material for the student who has learned many 

 principles, but must also gain self-reliance in the appli- 

 cation of the knowledge he has acquired. The problems 

 given cover a wide range, and include exercises in 

 structures, machines, strength of materials, and higher 

 applied mechanics generally. The diagrams are well drawn 

 and are clearly dimensioned. Many of the problems bear 

 the stamp of novelty, and are suggestive of others on the 

 same Hnes. Students preparing for the final engineering 

 examinations of any of the universities should find the book 

 useful. 



Engineering for December 8 contains an account of a 

 peat-gas plant which has been working at Portadown, in 

 Ireland, since September last with results which are re- 

 ported to be quite satisfactory. The plant works with air- 

 dried peat, and consists of two producers of 200 brake- 

 horse-power capacity each, together with coke-scrubber, 

 tar-extractor, sawdust scrubber, exhauster, and expansion 

 box. The peat is fed in block form into a hopper above 

 the producer, whence it falls into the producer itself as 

 combustion proceeds. The gas is drawn off through the 

 coke-scrubber and washer to the tar-extractor, where the 

 tar is extracted under centrifugal action. It then passes 

 on to the sawdust scrubber, and is delivered to the gas- 

 holder by a high-speed fan, which draws it through the 

 plant. The heating value is about 140 British thermal 

 units. This plant has replaced a Mond-gas plant by which 

 power was formerly provided, and figures are given in 

 comparison of the cost of the two methods of power-gas 

 production. The net expense for fuel in the peat-gas plant 

 is 4Z. 5s. per week. The anthracite used in the Mond-gas 

 plant cost 13Z. 165. 3d. per week. The plant has not been 

 running sufficiently long to ascertain definitely whether a 

 slight increase in labour may be necessary ; but, allowing 

 40Z. per annum for such a contingency, under these con- 

 ditions at a factory of 500 looms, employing 500 to 600 

 hands, a saving in the fuel bill of about 438Z. would 

 result. The plant was constructed by Messrs. Crossley 

 Brothers, Ltd., of Manchester. 



A SECOND French edition of the rirst part of vol. i. of 

 Prof. O. D. Chwolson's "Treatise on Physics" has been 

 published by MM. A. Hermann et Fils, of Paris, at the 

 price of 17 francs. As was the case with the first edition, 

 the translation is the work of M. E. Davaux, and is based 

 on the Russian and Gerni.ni (ditions. In this case, too, 

 additions and notes have been made by MM. E. and f- 

 Cosserat. The previous edition was reviewed in tli> i--ii' 

 of Nature for February 15, 1906 (vol. Ixxiii., p. ^c^). to 

 which reference may be made. 



OUR ASTRONOMICAL COLUMN. 

 Sciiaumasse's Comet, iqii/i.— From the Nice and the 

 Arcetri observations of comet 1911/1, on November 30, 

 December 1 and 2, M. F"ayet has calculated a set of 

 elements, which is published in a supplement to No. 4541 

 of the Astronomischc Ncuhrirhtcu. The elements give 

 Ffbruarv 5, i<)iJ. 's iln dai. ni |)eriheIion passage, and, 

 as will ix'sr.n lioni lii' . \iia. i Irom the ephemeris, given 

 below, the comet is now getting nearer to both the earth 

 and the sun. 



Ephemeris J2h. (M.T. Paris). 



191 1 a(irue) « (true) log r log ^ i/r^S^ 



h. m. . / 



Dec. 12 ... 13 556 ... -f- 3 6 ... 01611 ... 02459 ... 015 



,, 16 ... 14 II-2 ... -h 2 8 ... 01506 ... 0-2352 ... 017 



,, 18 ... 14 27-2 ... + 1 9 ... 01403 ... 02252 ... 019 



„ 22 ... 14 354 ••' + o 39 



