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.^NATURE 



[November 24, 1910 



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merits) ; and (5) pilot balloons (without instruments). The 

 use of Assmann's aspirating-psjchrometer in manned 

 balloons, and his employment of rubber both in registering 

 dnd pilot balloons in lieu of paper, have proved of the 

 greatest value. The author shows that much new light has 

 been thrown upon questions relating to the general circula- 

 tion of the atmosphere by the' important discovery of the 

 inversions of temperature at great heights and the exist- 

 ence of the isothermal layer, not only in our latitudes, but 

 also in polar and tropical regions. At moderate heights 

 these inversions play an active part in thunderstorm 

 phenoniena. 



The October number of Himmel und Erde contains an 

 account of a popular lecture on the present position of 

 wireless telegraphy, delivered six months ago by Dr. Karl 

 Strecker, of the Imperial Post Office, Berlin. The account 

 is well illustrated by diagrams, and is one of the best 

 popular introductions to the subject we have seen. The 

 author commences with the up-and-down oscillations of a 

 weight supported by a spring, and the property such an 

 arrangement has of setting in oscillation a sirriilar arrange- 

 ment suspended from the same beam as the first. By 

 simple steps he passes to the oscillations of electricity in 

 two conducting rods separated by a spark-gap, and to the 

 way in which a duplicate apparatus at a distance will 

 pick up the oscillations. The defects of the earlier 

 apparatus are explained, and it is shown how in succession 

 the means of detection of the oscillations and the means 

 of producing them have been improved by the introduc- 

 tion of the coherer and by the utilisation of the oscilla- 

 tions produced by a cooled electric arc. Even the problem 

 of privacy is not overlooked, and it seems the author 

 considers rapid and prearranged changes of frequency of 

 the oscillations as the future solution of the difficulty. 



The discovery by Messrs. Cotton and Mouton three 

 years ago that a liquid may be rendered double refracting 

 by the action of a magnetic field redirected attention to 

 the Kerr, effect, and as a result we now have theories 

 which attempt to explain, both effects. Prof. Voigt in his 

 " Magneto- und Elektro-Optik " traces them to a direct 

 effect of the electric or magnetic field on the electro- 

 magnetic oscillations which constitute light, while Prof. 

 I.. Natanson, in Ihe June number of the Bulletin of the 

 Academy of Sciences of Cracow, treats them as due to 

 the directive action of the field on the electrons oscillating 

 within the molecules. In the September number of Le 

 Radium Prof. Langevin extends his theory of magnetisa- 

 tion so as to cover the two effects. According to him, the 

 molecules of the liquid have axes along which the polari- 

 sation is an electric, and the magnetic moment in a 

 magnetic field have values which differ from those in 

 diicctions at right angles, ^olopropy of the molecule 

 once secured, either on Prof. Natanson 's or Piof. 

 Langevin 's theory, the investigation of the effects proceed 

 along lines similar to those of Dr. T. H. Havelock's 

 Royal Society paper of 1907, and leads to results in agree- 

 ment with observation — that the amount of the double 

 refraction is proportional to the square of the field, and 

 the dispersion is expressed by Cauchy's formula. 



An interesting paper on the development of road loco- 

 motion in recent years was read by Mr. L. A. Legros at 

 the Institution of Mechanical Engineers on Friday, 

 November 18, It is difficult to realise the enormous in- 

 crease in the use of the cycle both for pleasure and busi- 

 ness purposes. It is estimated that about one person in 

 every fifteen of the entire population of the United 

 Kingdom is a cyclist. Post Office cycles cover a distance 

 NO. 2143, VOL. 85] 



of 10,000 miles per annum per machine. The total number 

 in use for postal purposes is 11,400. It is notewoFthy. that 

 in the total mileage which has been run since the servicf- 

 was instituted, viz. about 600,000,000 miles, no fatal 

 accident has occurred by the failure of any portion of a 

 bicycle. The author estimates that the various publii 

 service horsed vehicles in London, will become extinct a> 

 follows: — the horse-tramcar at the end of 1912 ; the horse- 

 orhnibus at the end of 1913 ; the hansom cab at the end 

 of 1913 ; the four-wheel horse-cab before the end of 192 1. 

 The paper contains many useful suggestions regarding the 

 management of traffic in London streets. 



An illustrated article on the removing of the wreck of 

 the Quebec Bridge appears in the Engineer for 

 November 18. The contract for clearing the site was 

 awarded last December to Messrs. Charles Koenig and 

 Co., of Quebec, and about half the quantity, viz. 5000 

 tons, has now been removed. A large amount of cutting 

 has had to be done, and the choice of either dynamite or 

 o.xyacetylene for cutting a member is governed very largely 

 by local conditions. Where the latter method has been 

 used to greatest advantage has been in cutting up the 

 heavy chords and posts into pieces that could be handled 

 by the derricks, which have a capacity of not more than 

 10 tons. One web, 4 feet 6 inches deep, with a section of 

 190 square inches, was cut in 205 minutes with a consump- 

 tion of 112 cubic feet of gas. In cutting eyebars it was 

 found that with a stream of pure oxygen gas one square 

 inch of metal could be cut, on an average, in 5I seconds, 

 with a consumption of 0-4 cubic foot of gas, at a cost of 

 1-2 cents for the ox3'gen gas. Since the beginning of 

 operations some 50,000 cubic feet of gas have been con- 

 sumed, or an average of 10 cubic feet per ton of material 

 removed. 



Messrs. Schott and Gen, of Jena, have sent us a copy 

 of a well-illustrated catalogue of the new Jena glass 

 laboratory requisites they are now in a position to supply. 

 Extracts are published in the catalogue from a report from 

 the Imperial Physico-Technical Institute, Charlottenburg, 

 made after subjecting the new ware .to various tests, and 

 they indicate that these requisites, in comparison with 

 older Jena glasses, have an increased power of resistance 

 to sudden changes of temperature combined with a. reduc- 

 tion of the amount of alkali given off into aqueous fluids. 



OUR ASTRONOMICAL COLUMN. 



The Tot.\l Eclipse of the Moon, November 16. — Not 

 for man}' years have the conditions for observing a total 

 eclipse of the moon been so generally favourable as they 

 were on November 16. Reports from all over the country 

 show how generally they were taken advantage of and 

 appreciated, although, of course, " no details of special 

 scientific interest are yet published. Several meteors were 

 observed before and during the eclipse, Mr. E. A. Martin 

 having observed one at 6h. 55m. p.m. from South Nor- 

 wood. Its path was from north-west to south-east, its 

 colour reddish-yellow, and it was especially noticeable by 

 reason of its extremely leisurely movement. Two faint 

 meteors travelling in the same direction were seen from. 

 Gunnersbury during the eclipse. Madam de Robeck, 

 writing from Naas, Ireland, states that the eclipse was 

 a beautiful spectacle, and that she saw three meteors. 

 One of these was a fine specimen, which travelled in a 

 south-westerly direction from an apparent radiant just 

 below the eclipsed moon. The penumbral shadow was 

 barely discernible until after 10 p.m., when the relative 

 darkening of the south-east limb could be detected. A 

 slight flattening of the limb appeared to take place some 

 minutes before the actual shadow could be seen on the 

 disc, and throughout the eclipse the various prominent- 



