January 6, 192 1] 



NATURE 



609 



(Aachen) and Frankfort the direction of the wind at 

 the surface is practically the same as at an elevation 

 of 1000 metres, while at Strasbourg the wind at the 

 surface is usually backed two points from the wind at 

 1000 metres. 



When the interpretation of crystal structure on the 

 basis of close-packed spheres was put forward by 

 Barlow and Pope in 1906 it was suggested that the 

 sphere of influence of each atom in a given crystal 

 was approximately proportional to its valency, but 

 that these spheres of influence varied in size in a 

 scries of isomorphous crystals in such a way as to 

 preserve the proportionality of their individual 

 volumes to the valencies, whilst the sum of their 

 ■ olumes varied with the molecular volume of the 



'inpound. Prof. W. L. Bragg's study of the structure 

 of crystals by means of X-ray analysis, on the other 

 hand, led to the conclusion that each atom has a 

 constant sphere of influence, the atomic diameters of 

 some of the common elements being, for instance, as 

 follows : 



F =1-35 A. O =1 30 A. Li =r5oA. Be =iisA. 



CI » 2"lo S =205 Na=i77 Mg=|-42 



Kr = 2-38 Se=2-3S K =207 C«=l7o 



I =:2!!o Te = 266 Rb=2-25 Sr =195 



Cs =2'37 Ba =2MO 



A crucial test of these alternative views can be m.3do 

 most readily by carrying out an X-ray examination 

 of an isomorphous series, and this has now been 

 'lone in the case of calcite and the isomorphous car- 

 mates of manganese and iron, the Laue patterns 

 irom which have been analysed by a novel geometric 

 method by R. \V. G. VVyckolT (\mer\can Journal of 

 Science [iv], vol. 1., pp. 317-60, November, 1920). 

 The following results were obtained : 



CCOj MnCOi Und KeCO,) 



Iii5tance from carbon to oxygen l°2l (I 42) f2i{f^i) 



,, ,, metal 3-04(247) 2'83 (2'24and 217) 



>. oxygen ,, 2-30 (2-35) |-96(2I2 „ 205) 



In this table the distances from carbon to oxygen are 

 constant, whilst the distances from carbon to mct.il 

 and from oxygen to metal are about 026 A. and 

 0-34 A. greater for calcium than for manganese and 

 iron. It should, however, be noted that most of 

 these data differ considerably from those given by 

 Bragg (which arc shown in brackets in the table), 

 the deviations rising to 06 A. in the distance from 

 carbon to metal, i.e. nearly three times as much as 

 the variation on p.i$sing from calcium to manganese 

 or iron. 



In Science for October 15 Mr. J. J. Willaman, of 



the University of Minnesota, directs attention to the 



possibility of utilising artichoke and dahlia tubers as 



i>urces of fructose, which could be used, in place of 



rdinary sugar (sucrose), as a sweetening agent. 



I hese tubers contain the carbohydrate inulin, which 



"n hydrolysis by acids is converted into fructose 



i-vulosc), just as starch is similarly convertible into 



iucose (dextrose). Taking an average crop of arti- 



loke tubers at 40,000 lb. per acre, and assuming a 



( ovcry of 10 per cent, of inulin, Mr. Willaman 



ates that it should be possible to obtain about 



4(xx) lb. of fructose per acre, which is nearly 



equal to the yield of sucrose from a good crop 



NO. 2671, VOL. 106] 



of sugar-cane and about twice the yield of glucose 

 syrup from an average crop of maize; fructose, more- 

 over, is sweeter than either sucrose or glucose, so 

 that artichokes would appear to have a distinct advan- 

 tage over either sugar-cane or maize as a source of 

 sweetening material. The author realises that the 

 matter may not be quite so simple as it looks, and 

 he appeals for the inauguration of research by some 

 official or industrial organisation to ascertain whether 

 a presentable fructose can be made from artichokes. 

 These tubers have been used in Germany as a source 

 of alcohol, but that is a simpler proposition than the 

 manufacture from them of a serious competitor with 

 cane-sugar, .\rtichokes grow well in England, as 

 hundreds of allotment-holders discovered during the 

 war ; there are plenty of British chemists familiar 

 with the chemistry of carbohydrates, and our large 

 consumption of sugar is met almost entirely by im- 

 ports. In view of this, the Department of Scientific 

 and Industrial Research might do worse than take 

 Mr. Willaman 's suggestion mto serious consideration, 

 if it has not already done so, and, if there is anything 

 in it, arrange to have the necessary research work 

 done in this country. 



We have received a Physical Department Paper 

 issued by the Egyptian Ministrv of Public Works on 

 "The Effect of Turbulence on River-discharge 

 Measurements," forming aij addendum to a Report 

 on Nile Gauge Readings and Discharges published 

 in March last. Mr. Hurst, Controller of the Physical 

 Department, has prepared this note to prevent any 

 misconception which might arise on the statement of 

 certain views attributed to Mr. Craig, of the Egyptian 

 Survey, in the earlier publication. The Survey of 

 Egypt carried out a long series of river-discharge 

 measurements at Sarras, in the Sudan, the results 

 of which, after making all necessary allowances, 

 showed a considerable divergence from the readings 

 at the .Aswan Dam, amounting to about ij per cent. 

 In 1912 Mr. Craig put forward the suggestion that 

 the variation might be due to the effect of turbulence 

 in the flow, and showed mathematically that reduc- 

 tions in apparent volume might have to be made 

 amounting to as much as 20 per cent, during flood 

 and to 10 or 15 per cent, when the river was low. 

 Experimental investigation, however, has demon- 

 strated that the correction for turbulence at the low 

 stage of the river is negligible. .After alluding to 

 some further experiments now being carried on, the 

 paper concludes :— " The effect of turbulence at the 

 low stage is now settled, and the probability is that 

 the amount of turbulence present in the Nile in 

 flood at well-chosen sites will not necessitate any 

 corrections of practical importance. The cause of the 

 difference between the discharges at Sarras and Aswftn 

 still remains to be found." 



We have received from M<N.,rs. J. Woolley, Sons 

 and Co., Ltd., of Manchester, a copy of their 

 "Scientists' Reference Bcmk and Diary," price 3*. M. 

 The book contains much interesting and useful in- 

 formation in addition to that usually found in diaries. 

 The first section deals with the physical sciences, and 

 contains a short article on recent advances in physics; 

 another portion is devnte<l to chemical tables, and 



