464 



NA TURE 



[October 14. 1909 



analogy with other continental areas, but that the effects 

 of the South African plateau and of the great wind move- 

 ment alter the circumstances. The present tables, based 

 on data for two years, are, however, only considered as a 

 first approximation. 



With reference to suggested reforms in meteorological 

 methods, we referred in a recent issue to a proposal made 

 by Prof. A. G. McAdie in the V.S. Monthly Weather 

 Review of November, 1908, to adopt the centigrade (not 

 Celsius) scale and the metric system for temperature, 

 wind, rain, &c., and 1000 on an arbitrary scale of units 

 as the equivalent of the normal atmospheric pressure of 

 760 mm. This proposal has led to several interesting com- 

 munications on the subject in the Monthly Weather Review 

 of March last. Mr. M. E. J. Gheury (Eltham) prefers, for 

 reasons given, the units at present generally adopted for 

 meteorological observations in this country. Mr. H. H. 

 Clayton (Blue Hill, U.S.) prefers the metric system, but 

 with regard to temperature he renews a suggestion, made 

 in Nature in 1899 (vol. Ix., p. 491), that the Kelvin thermo- 

 meter scale (freezing point 273°, boiling point 373°) should 

 be used, and he points out that the adoption of this scale 

 with the metric system was recommended by a committee 

 of the British Association in 1904. Prof. Koppen (Ham- 

 burg) approves of the use of the metric and centigrade 

 systems by England and America, but would express all 

 barometric measurements by ordinary general units of 

 force, taking as unit the product gram X acceleration of 

 gravity. In connection with the above notes it may be 

 stated that from the commencement of this year the 

 Meteorological Office has adopted centigrade degrees on the 

 absolute scale (from —273°) and pressure in C.G.S. units, 

 or megadynes per square centimetre, as most suitable for 

 the publication of values in the investigation of the upper 

 air. 



No. 15 of the Verhandliiitgen der dcutschen physik- 

 alischen Gesellschaft contains two contributions from Prof. 

 W. Nernst and his pupil. Dr. H. Levy, dealing with the 

 physical properties of water from the thermodynamic point 

 of view. Assuming that the deviations of water vapour 

 from the " perfect gas " laws are due to the formation 

 of a certain proportion of double molecules in the vapour, 

 they show that it is possible to give expressions for the 

 density and pressure of the vapour and the latent heat 

 of evaporation of the liquid, within the interval 0° C. 

 to 100° C, the latent heat of fusion of ice, and even for the 

 variation of the specific heat of water with temperature, 

 which show an accuracy far greater than has been attain- 

 able with the help of any previous theory. 



Some experiments by Prof. Rateau on fluid pressure on 

 inclined planes are discussed in an article in Engineering 

 for September 17. The mathematical solution for an ideal 

 fluid shows that a portion of the fluid is always deviated 

 so as to pass over the leading edge, whatever may be the 

 inclination of the plane. Rateau's experiments show that, 

 for considerable angles of incidence, the fluid actually spills 

 over both edges, whilst for smaller angles the flow takes 

 place wholly past the trailing edge. Using a rectangular 

 plane 30 by 50 centimetres by 1-25 millimetres thick, from 

 o to 29 degrees the flow is solely over the trailing edge ; 

 from 29 to 36 degrees the conditions are absolutely un- 

 stable ; afterwards a proportion regularly escapes past the 

 leading edge. Further, the smaller the angle of inclination 

 the nearer does the centre of pressure lie to the leading 

 edge of the plane, the limiting value for the above plane 

 being 0236 of the width of the plane for zero inclination. 

 A plate having a flat ship-shaped section shows a very 

 NO. 2085, VOL. 81] 



marked retrogression of the centre of pressure at inclina- 

 tions less than 7 degrees, the centre of pressure moving 

 rapidly towards the trailing edge. A blast of air was used 

 in these experiments, and results were also obtained for 

 the total pressure and for the friction. 



From an article on the Paris Aviation Exhibition in 

 Engineering for October i we note a point which may 

 possibly require more attention than it has hitherto re- 

 ceived. In the case of an engine running with no fly- 

 wheel except the propeller, the blades near the root may 

 be subject to a considerable stress alternating with every 

 revolution of the engine. The amount of this stress will 

 depend on the number of cylinders the engine has, and it 

 may be necessary to make the propeller-blades consider- 

 ably stronger with two- and three-cylindei" engines having 

 no fly-wheel than with others having a more even turning 

 moment. Wooden propellers seem more in favour than 

 those of metal, and probably are more suitable, as wood 

 is well able to withstand the above-mentioned stresses, and 

 it is easy to make the blade strong at the root without 

 excessive weight. The wreck of the dirigible Republiqtie 

 and the death of four men composing her crew, owing to a 

 broken propeller, shows that danger from this cause is not 

 imaginary, and the results in an aeroplane would probably 

 be at least equally disastrous. We also note from the 

 same article that although the cross-Channel flight and 

 the record for distance have been performed with air- 

 cooled motors, the water-cooled engines are in a very 

 large majority at the e.xhibition. Weights per horse- 

 power range from 22 lb. in the Gnome to 75 lb. in the 

 Renault, both being air-cooled. The water-cooled engines 

 range from 4 lb. in the Darracq to 6-i lb. in the Bayard, 

 excluding radiator and water. 



The Carnegie Institute of Washington has now pub- 

 lished the eighth volume of the " Index of Economic 

 Material in Documents of the States of the United States." 

 It deals with the State of Illinois, and covers the years 

 1809-1904. This index has been prepared by Adelaide R. 

 Hasse, of the Librarian Department of Public Documents 

 in the New York Public Library, and deals only with the 

 printed reports of administrative officers, legislative com- 

 mittees, special commissions, and governors' messages. 

 The term " economic " has been given a liberal interpreta- 

 tion, and the index will constitute a useful addition to the 

 resources of students of American history. 



We are asked to state that a new edition (the third) of 

 " A List of Official Chemical Appointments " is being 

 prepared by the registrar and secretary of the Institute of 

 Chemistry, and that corrections and additions should be 

 sent as soon as possible to the registrar of the institute, 

 30 Bloomsbury Square, W.C. Suggestions which may 

 increase the usefulness of the list will be carefully con- 

 sidered. 



SiN'CE the appearance in the last number of Nature of 

 particulars as to forthcoming books of science, informa- 

 tion has reached us of the following additional works :— 

 In Agriculture. — " Principles of .Agriculture : a Text-book 

 for Lecturers on Agriculture, Rural Schoolmasters, Young 

 Farmers, and Students of Agriculture," J. M'Cutcheon, 

 illustrated (E. and S. Livingstone). In Biology. — " Window 

 and Indoor Gardening," T. W. Sanders; "Mushrooms 

 and their Cultivation," T. W. Sanders; " Bees for Profit 

 and Pleasure," H. Geary (W. H. and L. Collingridge) ; 

 " The Mammals of Somaliland : a Book for Naturalists and 

 Sportsmen," R. E. Drake-Brockman, illustrated (Hurst 

 and Blackett, Ltd.); "The Mutation Theory," Dr. H. 

 de Vries, 2 vols., illustrated tKegan Paul and Co., Ltd.). 



