NATURE 



[July 



1910 



iliermometers in windows and in screens, such as are now 

 generally used in this country, with the view of a future 

 critical discussion of temperature conditions in Germany. 

 The first part of the inquiry, contained in the report for 

 1908, showed that the introduction of the window screen 

 about the year 1880, instead of the unprotected window 

 exposure adopted at all stations prior to that date, did not 

 interrupt the homogeneity of the observations. In the 

 second part of the inquiry, experiments carried out at 

 Potsdam as regards window exposure and exposure in 

 " Stevenson screens," now used at about two-thirds of the 

 German stations, show that not only the readings obtained 

 bv these two methods, but those at some of the more 

 recent stations, are not strictly comparable. The differ- 

 ences are relatively small in coastal cloudy and windy 

 weather, but considerably greater in dry and sunny inland 

 districts. For details of this interesting discussion refer- 

 ence must be made to the tables and curves of the mean 

 daily range shown for each month in the original paper. 



Every month sees a fresh issue of the bulletins from the 

 Bureau of Entomology of the United States Department 

 of .'\griculture. In Circular 119 Mr. Webster describes 

 the clover root-borer {Hylasiinus obscurus, Marsham), 

 which has been introduced from Europe and become estab- 

 lished in helds of red clover in the eastern States and else- 

 where, causing considerable damage. The life-history has 

 been investigated, but no method of extermination could be 

 discovered. Mr. Ainslie deals with the large corn-stalk- 

 borer (Diatraea saccbaralis, Fab.). This insect burrows 

 in the stalks of maize close to the ground, and so weakens 

 them that they often break off in a strong wind. It was 

 •originally a sugar-cane pest, and came from the West 

 Indies and from Central and South America, but for some 

 time now has devoted its attention to maize. 



The presidential address delivered by Prof. M. C. Potter 

 before the British Mycological Society has now been issued, 

 and deals with bacteria in their relation to plant pathology. 

 The subject has been much neglected both by bacteriologists 

 and mycologists, in spite of the fact that at least ten plant 

 diseases are considered to be caused by bacteria. They 

 are pear-blight (Bac. amylovorus), yellow disease of 

 hyacinth (Pscudomonas hyacinihi), canker of the olive 

 {Bac. oleae), corn-blight {B. zeae), potato wet-rot (B. 

 solamperda), soft rot of hyacinth (B. hyacinthi-septicus), 

 tacteriosis of the vine (B. uvae), cucurbit wilt (B. trachei- 

 philus), brown rot of Cruciferae (Pseudomonas campestris), 

 and potato and tomato disease (Bac. solanacearum). A 

 ■discussion of the problem is given and a bibliography is 

 appended. 



The Chemical Society's Journal for May contains two 

 papers by Mr. H. E. Watson on the molecular weights of 

 helium, neon, krypton, and xenon. The neon was prepared 

 in a state of exceptional purity by fractionating 40 litres 

 of a mixture of helium and neon over charcoal at the 

 temperature of liquid air, and full details are given of the 

 methods used both in effecting the purification and in 

 measuring the density of the gas; repeated determinations 

 with various highly purified fractions gave values ranging 

 from 0-8997 '° 0-9006, the mean of eleven values being 

 •0-9002. In the case of helium only two measurements 

 were made, giving the values 0-17830 and 0-17814, mean 

 ■0-1782 ; as the gas which was weighed amounted only to 

 .0-05 gram, the experimental error is placed at i part in 

 2000. Reduction of observed densities to zero pressure 

 gave for the molecular weights of the gases of the series 

 the values: — heUum, 3-994; neon, 20-200; argon, 39-881; 

 krypton, 812-92 ; xenon, 130-22. 



NO. 2123, VOL. 84] 



.■\lthough the use of oil as a means of securing more 

 rapid dissipation of the heat generated in transformers has 

 become almost universal in the case of large transformers, 

 very little information has been available as to the relative 

 merits of the various oil- and air-cooling devices. This 

 information is now supplied in a paper by Mr. R. D. 

 Gifford, of the University of Birmingham, which will be 

 found in the May number of the Journal of the Institution 

 of Electrical Engineers. His measurements show that if 

 the cooling effect of the air in the case of a transformer 

 be taken as unity, that of the free air would be about i-i 

 and that of a strong air blast about 2. With oil cooling 

 the effect rises to about 3, and if the oil itself is cooled 

 by the passage of cold water through a worm immersed 

 in the oil, the cooUng effect becomes 6 or 7. 



Bulletin No. 40 of the Engineering Experimental Station 

 of the University of Illinois consists of an account of 

 measurements made by Messrs. J. K. Clement and C. M. 

 Garland of the heat transmitted through a steel tube of 

 i^-inch external diameter, with walls J-inch thick, from 

 steam outside to water inside running through the tube. 

 The temperature of the outside surface of the tube was 

 measured at two points by means of thermojunctions of 

 copper-constantan placed in small holes drilled in the tube. 

 The temperatures of the incoming and outgoing water and 

 of the steam were determined by mercury thermometers. 

 Curves are given showing the variation of the heat trans- 

 mitted with the velocity of the stream of water and with 

 the temperature of the steam, and the resistance to the 

 transmission of heat is shown to be almost entirely con- ' 

 centrated in the films of stagnant steam and water in 

 contact with the surfaces of the steel tube. The authors 

 regard the present communication, not as one devoted to 

 new facts, but as a demonstration of the utility of their 

 method of measurement, and propose to apply the method 

 to the investigation of problems connected with steam 

 boilers. We should like to point out that a good deal of 

 work has already been done in this direction both in this 

 country and in others, and it is to be hoped that the new 

 experiments will be directed to the solutions of problems 

 which have not been already dealt with by Mr. Jordan or 

 by one or other of the experimenters mentioned in Prof. 

 Dalby's bibliography of the subject contained in the Journal 

 of the Institution of Mechanical Engineers for last year. 



We learn from Engineering of June 24 that Lloyd's 

 Register of British and Foreign Shipping is about to 

 issue rules for internal-combustion engines for marine 

 purposes. The rules are divided into four headings. The 

 section concerning construction strongly enforces the 

 importance of accessibility for examination and repair, and 

 requires that engines of more than 60 brake-horse-power, 

 which are not reversible, and are manceuvred by clutch, 

 must be fitted with a governor or other arrangement to 

 prevent the racing of the engine when declutched. The 

 cylinders are to be tested by hydraulic pressure to twice 

 the working pressure to which they will be subjected ; the 

 water-jackets of the cylinders to 50 lb. per square inch, 

 and the exhaust-pipes and silencers to 100 lb. per square 

 inch. The tables are comprehensive, embracing smooth- 

 water and open-sea service boats, and engines of 4-stroke 

 cycle and 2-stroke cycle. Separate fuel-tanks are to be 

 tested, with all fittings, to a head of at least 15 feet of 

 water. Oil-fuel pipes are to be of annealed seamless 

 copper, with flexible bends, conical joints metal to metal, 

 with a cock or valve at each end of the pipe conveying 

 the fuel from the tank to the carburettor or vaporiser. 

 The machinery is to be submitted for survey annually, 

 and practically all parts are to be examined, the fuel- 



