December 2, 1909] 



NA TURE 



139 



various laboratory classes in the institute. It is, we notice, 

 made clear that the teachers in charge of the laboratories 

 concerned are at liberty to modify the suggested scheme to 

 meet their special needs. The notes should be of assist- 

 ance to young demonstrators who are gaining experience 

 as indicating what a successful teacher has found to be a 

 good plan of procedure, but any slavish copying of a hard 

 and fast routine would be undesirable in most cases. The 

 notes have been printed for distribution among the staff 

 at Belfast. 



The Physikalische Zeitschrift for November lo, and 

 part x.K. of the Berichie der deutschen physikalischen 

 Gesellschaft, are both devoted to reports of the physical 

 papers read at the Versammlung deutscher Naturforscher 

 held at Salzburg in September. The former periodical 

 gives, in addition, reports of the discussions following the 

 reading of the papers, ."^n afternoon sitting was devoted 

 almost entirely to papers on the problems which arise in 

 the treatment of radiation and in the building up of 

 electrodynamics ^n the principle of relativity. Prof. 

 Sommerfeld discussed the composition of velocities, and 

 Dr. M. Born the dynamics of electrons on the theory of 

 relativity. Prof. Einstein gave an interesting account of 

 the development of our views of the origin and constitu- 

 tion of radiation, an account which will be of special value 

 to those who are looking forward to the appearance of 

 .Sir Joseph Larmor's recent Bakerian lecture. 



Messrs. Elliot Brothers are making an accelerometer 

 and gradient measurer, devised by Mr. H. E. Wimperis, 

 which is both ingenious and simple and is free from dis- 

 turbance by motions of any kind, except that of acceleration 

 in one direction or of tilting in the same direction. Two 

 vertical spindles are geared together so as to run in opposite 

 directions, and they are each eccentrically weighted, and 

 the weights are so placed that their motions in the direc- 

 tion marked upon the instrument are the same and conspire 

 in their effect, while those transverse to this direction are 

 opposite and neutralise each other's effect. One of the 

 spindles carries a copper disc damped by a permanent 

 magnet, an index moving over the scales of acceleration 

 and gradient, and a controlling hair-spring. Such a com- 

 bination is unaffected by rotational movement or by rota- 

 tional acceleration of the instrument about any axis what- 

 ever ; it is also unaffected by transverse or vertical motion 

 or acceleration, or by longitudinal steady motion. It is 

 therefore affected by longitudinal acceleration or by fore 

 and aft gradient alone. As either fore and aft tilting and 

 fore and aft acceleration are of necessity both operative, it 

 is impossible merely by taking a reading to tell how much 

 of the deflection is due to each if the two causes act simul- 

 taneously. The user is therefore instructed how to arrange 

 that one of the effects is zero, or, if they both act together, 

 to determine one by an independent observation. A large 

 number of illustrations of the utility of the instrument are 

 described, including power of engine, efficiency of brakes, 

 friction when running idle, and measurement of gradients. 



We have received the first part of Dr. Ludwig Koch's 

 " Pharmakognostischer .\tlas " (Leipzig : Gebruder Born- 

 traeger), which is intended to form a supplement to the 

 recently completed work by the same author on the micro- 

 scopical analysis of drug powders. The atlas will deal 

 mainly with the crude drugs of the German Pharmaco- 

 poeia, and will contain illustrations and descriptions of 

 sections cut in various directions, the illustrations being 

 sufficiently extensive to show, not only the nature of the 

 elements that occur, but also their relative quantity. 

 Judging from the first part, the figures, so important in 

 a work treating of structural details, will leave nothing 

 NO. 2092, VOL. 82] 



to be desired in clearness or accuracy, and the descrip- 

 tions, though minutely detailed, will be readily intelligible. 

 The work promises to be one of the most valuable of its 

 kind, and to be indispensable to everyone interested in the 

 anatomical structure of drugs. 



Messrs. J. J. Griffin and Sons have issued their list 

 of chemicals manufactured by C. A. F. Kahlbaum, of 

 Berlin. In comparison with their previous list there has 

 been an expansion from 79 to 95 pages. As compared 

 with the German price-lists of Kahlbaum and Schuchardt, 

 the present list shows an increase of price amounting, in 

 the case of typical materials, to about 35 per cent., but as 

 the English prices include cost of freight, bottles, and 

 packing, the difference on small orders is not excessive, 

 and there can be no difi'erence of opinion as to the 

 advantages gained by having a stock of these materials 

 available in London for immediate use. 



The Journal of the Chemical Society for October con- 

 tains an interesting paper by Mr. R. W. Gray and Mr. 

 F. P. Burt on the atomic weight of chlorine. The work 

 is divided into three parts — a revision of the density of 

 hydrogen chloride, a re-determination of its volumetric 

 composition, and a study of its compressibility at 0° 

 between the limits 780 mm. and 150 mm. The density 

 was measured by an ingenious application of the con- 

 densing action of charcoal cooled by liquid air, as sug- 

 gested and used by Dewar and Jones. The gas to be 

 examined was condensed by liquid air, carefully purified 

 by fractional distillation, and transferred for measurement 

 of volume to a flask of 460 c.c. capacity surrounded by 

 ice and distilled water, and connected to a manometer ; 

 for measurement of weight it was connected to a charcoal 

 bulb having a capacity of only about 20 c.c. ; when cooled 

 with liquid air the charcoal absorbed the whole of the 

 hydrogen chloride, leaving a vacuum both in the weighing 

 and measuring bulbs, and by closing the bulb by a 

 stop-cock its weight could be determined at atmospheric 

 temperatures. The average density, after correcting for 

 adsorption of gas by the walls of the measuring bulb, was 

 found to be 1-63915 grams per litre. The volumetric 

 analysis, carried out by measuring the volume of hydrogen 

 set free by the action of aluminium on the gas, gave a 

 mean volume of 100790 vols, hydrogen from 2 vols, 

 hydrogen chloride. Combined with Morley's value for the 

 density of hydrogen, the authors' own value for the density 

 of hydrogen chloride, and Morley's value for the ratio of 

 oxygen to hydrogen, this gave the atomic weight 35-459- 

 A comparison of the densities of hydrogen chloride and 

 oxygen, both corrected for deviations from Boyle's law, 

 gave Cl = 35-46i. The mean value Cl = 3S-46o coincides 

 exactly with the mean of seven recent determinations rang- 

 ing from 35-452 to 35-466, and there can be little doubt that 

 the figure is substantially correct. 



The firm of Gauthier-Villars, of Paris, has published 

 the first of a series of volumes projected under the general 

 title "Savants du Jour." The present book deals very 

 appropriately with M. Henri Poincar^, whose work is 

 known to men of science everywhere. The frontispiece 

 to the volume is an admirable portrait of M. Poincar^. 

 The text is divided into seven sections ; the first is in the 

 form of a biography, which comprises the discourse by 

 M. Fr^d^ric Masson last January in response to an oration 

 by M. Poincar^ when received by the Acad^mie Franqaise, 

 a chronological list of the distinctions conferred upon the 

 subject of the work, and a list of the appreciative articles 

 upon his career which appeared in the French Press. The 

 succeeding six sections are concerned, respectively, with 



