^^:5;j92i.„ 



new electric larpp for the microscope has also been 

 designed for use with a "Pointolite," a half-watt, or 

 a pietal filament lamp. Another piece of apparatus 

 at a moderate price is the Beck photomicrographic 

 camera. 



Jh Sci^ence of March 25 Dr. I. Langmuir attempts 

 to rnodify the "cubical " model of the atom, in which 

 the outer electrons are supposed to be practically at 

 rest, so as to obtain the well-known results in con- 

 nection with spectra which were achieved by the 

 entirely different atomic model due to Bohr. It is 

 shown that on the assumption of a repulsive force 

 Fg = i/mr^{nh/27ry between the positive nucleus and 

 an electron, in addition to the Coulomb attractive force 

 Fj=Ze^/r^, the equations for the radius of the elec- 

 tronic orbit, the total energy in any stationary state, 

 qnd the frequency of revolution of the electron in 

 the Bohr atom are obtained. The symbols denote : 

 ni = mass of nucleus, Z« = charge on nucleus, r = dis- 

 tance between electron and nucleus, fi = Planck's con- 

 stant, and n is an integer denoting the quantum state 

 of the electron. The assumption of the particular law 

 of force for F, is, however, entirely arbitrary, and 

 was chosen to give the results obtained. 



At a meeting of the Institution of Civil Engineers 

 on April 19 a paper on "The Measurement of the 

 Discharge of the Nile through the Sluices of the 

 Assuan Dam " was jointly presented by Sir Murdoch 

 MacDonald and Mr. H. E. Hurst. The paper 

 describes a series of observations taken to determine 

 accurately the discharge by means of the volumes of 

 water passed into a masonry tank having a capacitv 

 of 22,000 cubic metres, which was constructed for 

 the purpose of forming a water-cushion to protect 

 the rock surface on the down-stream .side of the dam. 

 The results of the measurements, which are believed 

 to be correct within i per cent., showed that (a) for 

 a given opening the coefficient of discharge increases 

 as the head increases until, in the neighbourhood of 

 10 metres head, it becomes constant ; (b) for the small 

 openings, 1-5 and 20 metres, there is not much dif- 

 .ference between the coefficients for the same head, 

 and the coefficients for both openings attain prac- 

 tically the same maximum value ; and (c) for the 

 small heads there is a progressive decrease of coefficient 

 as the size of the opening increases. For heads 

 greater than 3 metres this effect is reversed, and the 

 coefficient increases with increase of sluice-opening. 

 Experiments were also made to determine the coeffi- 

 cients of discharge of other types of sluices of the 

 dam which differ in dimensions and in the levels of 

 their sills. The results of these experiments are stated 

 and discussed. Some observations are added on the 

 accuracy of Gurley current-meters. 



The lighting of ships at sea, which was the subject 

 of discussion at the last meeting of the Illuminating 

 Engineering Society, offers a number of interesting 

 problems. The society was fortunate in receiving the i 

 co-operation of representatives of the Admiralty and 

 of the Mercantile Marine Service Association, some of 

 whom gave interesting accounts of their difficulties 

 when oil-lanterns were the only illuminants available. 1 

 NO. 2688, VOL. 107] 



One gathers from the discussion that in many 'cases 

 the degree of light provided is much less, than that 

 usual on' land, and this must affect the safety and 

 efficiency of work in the hold of the ship. Among 

 special problems mentioned the lighting of this chart- 

 house and compass-dials deserves attention. Naturally, 

 concealed lighting is recommended in this case, one 

 approved method being the lighting of charts mounted 

 between sheets of glass by diffused light transmitted 

 from below. Another interesting question raised in 

 the discussion was the amount of light desirable on 

 the deck of a ship. Shipmasters were inclined to view 

 with disfavour the use of lights on deck, on the 

 ground that, in contrast with the dense surrounding 

 darkness, they would dazzle the eyes and interfere 

 with operations on deck in sailing-ships, as well as 

 affect the "look-out." It may be presumed, however,, 

 that this depends much on the nature of the lighting, 

 and that these objections would be less if the actual 

 sources could be effectually screened from view. To 

 a landsman the idea of working constanth- on a 

 violently moving ship in complete darkness seems in- 

 evitably accompanied by risk and inconvenience such 

 as moderate diffused lighting might diminish. 



We have received a copy of the first of a new series 

 of catalogues issued by the Science Museum at South 

 Kensington. It is intended that each catalogue shall 

 treat of a single group of the collections and contain- 

 illustrations of a few important objects ; by these 

 means the price can be kept within reasonable limits, 

 and the visitor need purchase no more than he actually 

 requires. Eventually the new series will cover the 

 whole of the collections in the museum and take the 

 place of the existing catalogues. The present part 

 (is.) deals with machine-tools and metal-working and! 

 wood-working machines ; descriptive and historical 

 notes are included. The compilers of the catalogue 

 clearly have in view the meeting of the requirements 

 of the visitor or purchaser who is interested in one 

 particular class of exhibits, and such will find that 

 the arrangement of the catalogue is good and that the 

 notes appended to each exhibit have been admirably 

 written. The value of the illustrations given may be 

 questioned ; these comprise twenty-two photographic 

 representations of selected machines. If the pur- 

 chaser is also a visitor he will certainly not require 

 these illustrations, having the actual model or 

 machine before him. If he is not a visitor photo- 

 graphs will help him in a minor degree only, and we 

 should like to suggest that a few line-drawings 

 showing the mechanism or the principle of 

 the mechanism would constitute a very valuable 

 addition to the catalogue. The idea of section cata- 

 logues is a sound one, and we hope that the authori- 

 ties will develop it in such a manner as to meet the 

 need which all students have experienced in visiting 

 the Science Museum, viz. to provide a record to which 

 reference may be made at any future time, confident 

 that the method of working and arrangement of any 

 of the exhibits will be understood. 



Messrs. A. Gallenkamp and Co., Ltd., of Surr 

 Street, Finsbury Square, E.C.2, have issued a list 

 (No. 71) of students' balances and weights of British 



