28o 



NATURE 



[April 28, 192 1 



year. Flood warnings are issued, and the results are 

 said to be very satisfactory. Rainfall data were re- 

 ceived for publication from nearly three thousand 

 stations for the year. 



In the January issue of the Journal de Physique 

 Prof. G. Bruhat, of the University of Lille, deals 

 with some conclusions with regard to the variation 

 of the specific heats of substances at low tempera- 

 tures, in partial accordance with experiment, to 

 which Nernst's theory of the solid or liquid state at 

 absolute zero leads. The values of the specific 

 heats of the same substance in different physical 

 states at the lowest temperatures for which observa- 

 tions are available cannot be held to confirm the 

 theory that the entropy of each modification tends to 

 the same value at absolute zero. All that can be 

 said at present is that Nernst's hypothesis is not 

 contradicted by observation. Prof. Bruhat also points 

 out that while the difference between the energies ot 

 two modifications of the same substance may be 

 expanded in a series in ascending powers of tem- 

 perature differences near the points of observation, 

 there is no justification for continuing this expansion 

 down to absolute zero. 



Mr. L. W. Austen, of the U.S. Naval Radio 

 Research Laboratory, contributes an interesting paper 

 to the Journal of the Washington Academy of Sciences 

 for March on the wave-front angle in radio-telegraphy. 

 He gives the results of experiments made with a 

 pivoted, straight-wire, antenna system mounted at 

 the top of a 55-ft. wooden pole in such a way that it 

 is capable of rotation about a vertical and a hori- 

 zontal axis. The results show that for wave-lengths 

 greater than 10,000 metres the deviation of the wave- 

 front from the vertical cannot, much exceed 3°. The 

 average value of the deviation of the waves from 

 Nauen, 3600 miles away, was 3-4°. It was found that 

 the waves from San Diego, although they passed over- 

 land for 2000 miles, were practically vertical. Ob- 

 servations were made to see whether the well-known 

 shift in the apparent direction of a sending station 

 at night as determined by a radio compass was accom- 

 panied by any corresponding phenomenon in the value 

 of the deviation of the wave-front. Although the 

 apparent direction of the station shifted at times by 

 as much as 30°, no appreciable change in the devia- 

 tion of the wave-front could be detected. 



There are many cases in engineering- in which 

 intense loading pressures are inevitable ; for example, 

 knife-edges, the line-contact of gear-wheels, the con- 

 tact pressure of the wheels of a locomotive on the 

 rails, etc. The results of a long investigation on 

 contact pressures and stresses are given in a paper 

 read before the Institution of Mechanical Engineers 

 on March 18 by Prof. E. G. Coker, K. C. Chakko, 

 and M. S. Ahmed. It is not possible to do justice 

 to this paper in a short note. The authors have 

 determined the stress distribution in a number of 

 cases, e.g. the distribution of stresses, over different 

 bearing areas, of a rectangular block pressed against 

 another flat surface of greater area by a load applied 

 at the centre of the opposite face. Another matter 

 investigated is the effect on the strength of tensile 

 NO. 2687, VOL. 107] 



test-specimens of the minute indentations required 

 for the attachment of extensometers and of the pres- 

 sures produced by the extensometer grips. The latter 

 case has been worked out completely, and diagrams 

 giving the stress distribution are included in the 

 paper. Prof. Dalby has abandoned the ordinary 

 method of attaching his extensometer and uses special 

 test-specimens having collars against which the 

 mechanism of the extensometer presses lightly. The 

 authors of the present paper have investigated the 

 effect of the collars of the Dalby specimen, and find 

 that there is ample justification for the use of this 

 form of test-piece. The paper constitutes an extremely 

 valuable record of the special methods of testing by 

 means of polarised light with which Prof. Coker's 

 name has long been associated. 



We welcome the first number of Photographic 

 Abstracts, for it fills a distinct gap in scientific litera- 

 ture. This is not the first attempt of the Royal Photo- 

 graphic Society to do work of this sort, but it is the 

 first time that the scheme has been properly financed 

 and arranged by an enthusiastic committee, assisted 

 by a large staff of efficient abstractors. The abstracts 

 are classified under eleven headings : — Colour photo- 

 graphy ; kinematography ; manufacture of photo- 

 graphic materials; photographic appliances (cameras, 

 etc.); photographic optics; photo-mechanical pro- 

 cesses ; radiography ; applications of photography 

 (astronomy, spectroscopy, photomicrography, etc.) ; 

 sensitometry, actinometry, photometry; theory of 

 photography; and photographic processes. This first 

 number is a distinctly creditable production, although 

 the publication committee apologises for not having 

 attained the ideal that it had in mind. 



Our knowledge concerning the chemical structure 

 of catechin has been considerably increased by the 

 series of papers recently published by Dr. Nierenstein 

 and his collaborators, entitled respectively "The Con- 

 stitution of Catechin, Parts I. -III.," and "Studies 

 in the Chroman Series " (Journ. Chem. Soc., 1920, 

 vol. cxvii., and 192 1, vol. cxix.). A successful effort 

 has been made to complete the work of Ryan and 

 Walsh, who attempted to decide between the chroman 

 structure proposed for catechin by A. G. Perkin and 

 the coumaran structure suggested by Kostanecki and 

 Lampe. Acacatechin and several derivatives have 

 now been synthetically produced and proved to be 

 identical with acacatechin and its derivatives obtained 

 from natural sources. This work of Dr. Nierenstein 

 proves that catechin is a chroman, but that the 

 chroman formula suggested by Perkin requires some 

 modification, as acacatechin is 2:4:6:3': 4'-penta- 

 hydroxy-3-phenylchroman. 



The new list of announcements just issued by 

 Messrs. Macmillan and Co., Ltd., contains the titles 

 of many works of scientific interest. Among the books 

 to be published between now and the end of June is 

 one by Sir Clifford Allbutt entitled "Greek Medicine 

 in Rome," being the Fitzpatrick lectures on the His- 

 tory of Medicine delivered at the Royal College of 

 Physicians of London in 1909-10, with other historical 

 essays. The essays will deal with Byzantine medicine ; 

 the Finlayson memorial lecture ; Salerno ; public medical 



