NATURE 



[March 4, 190Q 



(the last two having equal values). The weakest wind is 

 from N.W. During three years, 1S7J-5, a Robinson 

 anemometer was in opeiation ; the author has supplemented 

 his valuable work by a separate discussion of these data. 



The Memoirs of the Indian Meteorological Department, 

 vol. XX., part v., contain a laborious and valuable analysis, 

 by Mr, R. L. Jones, of the records of the anemograph 

 (Meteorological Office pattern) at the Madras Observatory 

 for eleven years, 1865-75. The tables give (i) the mean 

 hourly movement of air, irrespective of direction, for each 

 hour of the mean day of each month and for the year, and 

 the constants of the periodical formuljE ; (2) mean hourly 

 southerly and westerly components, and the constants of 

 the periodical formulae, with computed values in each case. 

 The chief features of the mean monthly air movement 

 (irrespective of direction) are (n) a nearly uniform increase 

 during the hot-weather period; (i!>) a more or less uniform 

 decrease approximately during the south-west monsoon 

 period; (c) a nearly uniform increase during the transition 

 period; (d) a nearly uniform decrease approximately during 

 the cold-weather period. • The curves showing the daily 

 variations exhibit a general resemblance to the daily 

 variations in air temperature. The resultant air movement 

 deduced from the southerly and westerly components is 

 (1) between north and east during the transition and cold- 

 weather periods ; (2) between east and south during the 

 hot-weather period ; and (3) between south and west during 

 the south-west monsoon period. 



Some of the troubles which have to be faced by engineers 

 in Egypt are described by Mr. J. B. Van Brussel in an 

 article on mechanical irrigation plants in the Engineering 

 Magazine for February. Part of the Nile irrigation station 

 at Wadi Kom-Ombo consists of a steel canal 5200 feet in 

 length and nearly semicircular in section, 20 feet diameter, 

 and about 12 feet deep. The canal is used for conveying 

 water from the service reservoir and distributing it to 

 earth canals, or culverts, and is made up of seventeen 

 sections, each about 310 feet long and constructed of 

 riveted steel plates 6 millimetres thick. The sections are 

 connected by expansion joints, and have a fall of level of 

 I centimetre. per 310 feet. Great difficulty was experienced 

 in preserving the level while building, owing to the action 

 of the wind passing through spaces where the dry founda- 

 tion sand had been removed for riveting, thus causing the 

 sand to drift and the wood cradles to sink. Often a whole 

 section would sink several inches in a night. During the 

 construction difficulty was also experienced due to unequal 

 expansion. According to the side of the canal on which 

 the sun was shining more strongly, the end of a section 

 would move out of the centre line to one side or the other 

 to the extent of as much as 4 inches. This movement 

 stopped when the earth was banked up round the steel 

 structural work, and the water began to flow through the 

 canal. 



The January number of Ion contains a translation of 

 the second memoir of the radium commission of the 

 Academy of Sciences, of Vienna. It deals with the evolu- 

 tion of heat by radium, and for it Drs. E. von Schweidler 

 and V. F. Hess are responsible. Experimenting with more 

 than a gram of radium-barium chloride enclosed in a 

 glass lube a millimetre thick, surrounded by a copper 

 vessel 5 millimetres thick, they have found that the heat 

 generated by i gram of pure radium in these circumstances 

 is 118 gram-degrees per hour. Ion, by a curious misprint, 

 omits to give its readers this number. 



An examination of the whole of the material at present 

 ' ailable on the variation of the refractive indices of 



mixtures of liquids with their composition has led Dr. 

 V. F. Hess, of the University of Vienna, to formulate, in 

 a paper which appears in the July, 1908, number of the 

 Sitzungsbcrichtc of the Academy of Vienna, a simple law 

 for the refraction constant of a mixture. If the excess of 

 the observed density of a mixture over that calculated from 

 the densities of the constituents be divided by the observed 

 density, and if the corresponding quotient for the refraction 

 constants be found, Dr. Hess shows that if it is assumed 

 that the two quotients for each mixture are proportional 

 to each other, the calculated values of the refraction con- 

 stants may, by a proper choice of the factor of proportion, 

 be made to agree very closely with observation. The 

 factor differs in value for each pair of liquids, changes a 

 little with change of temperature, but is practically the 

 same for all rays of the spectrum. .\nv one of the three 

 refraction constants at present in use may be used in the 

 calculations. 



The moving-coil galvanometer is now used so extensively 

 on account of its insensibility to outside magnetic disturb- 

 ances that Dr. M.' Rcinganum's article in the Physik- 

 alische Zeitschrijt for February i, describing two methods 

 of making the instrument suitable for measuring smaller 

 currents than it has been capable of measuring previously, 

 will be welcomed by many of our readers. In the first 

 method about 6 centimetres of soft iron wire, 033 milli- 

 metre diameter, is attached to the top of the coil outside 

 the strongest part of the magnetic field, and at riglit angles 

 to the lines of the field. In the second method a similar 

 piece of magnetised steel wire is attached to the coil parallel 

 to the field, but with its poles reversed. In each case the 

 sensitiveness of -the instrument is greatly increased, and 

 in one case described by the author, with the steel wire, it 

 was raised to ten times its original value witliout the 

 deflections ceasing to be proportional to the current passing 

 through the coil. 



In Reprint No. loi from the Bulletin of the Bureau of 

 Standards, v., 2 (Washington : Government Printing Office, 

 1908), Mr. Louis Cohen discusses the influence of terminal 

 apparatus on telephonic transmission. It is pointed out 

 that when a telephonic wave reaches the receiving instru- 

 ment part of it is reflected, and that the proportion of the 

 reflected and absorbed waves is a function of the frequency. 

 Thus every harmonic will be affected differently, and a 

 certain amount of distortion will be produced. The sub- 

 ject is eminently suited for the methods of mathematical 

 analysis which the author applies. The outcome of the 

 discussion is that in short-distance transmission the intro- 

 duction of a condenser into the circuit will improve the 

 transmission. This is the conclusion derived from an 

 application to a cable 30 km. long. For long-distance 

 transmission, taking as an example a length of 300 km., 

 the author finds that the condenser has little effect. 



Messrs. Macmillan and Co., Ltd., have published the 

 " Mathematical Papers for Admission into the Royal 

 Military Academy and the Royal Military College for the 

 years 1899-190S." The papers have been edited by Messrs. 

 E. J. Brooksmith and R. M. Milne, who have also pro- 

 vided answers. The price of the volume is 6s. 



Messrs. Crosby Lockwood and Son have just pub- 

 lished the second edition of Dr. J. Erskine-Murray's 

 " Handbook of Wireless Telegraphy." The original work 

 was reviewed in Nature of October 3, 1907 (vol. Ix.xvi., 

 p. 563). About fifty pages of new matter have been added, 

 and the whole text has been revised in the light of present 

 knowledge of the subject. 



CO. 2053, VOL. 80] 



