December 22, 1910] 



NATURE 



24. 



one hand, and by MM. Mac^ de L^pinay, Buisson, 

 and Rene Benoir, on the other. That made use of 

 bv M. Guillaume consisted in ascertaining the 

 measurements by mechanical contact — the old method, 

 in fact, of Lefevre-Gineau, modified by the refine- 

 ments of modern metrology. In each of the methods 

 the general problem was the same, namely, lo deter- 

 mine by lineal measures referred to the prototype 

 metre, the dimensions, and consequently the volume 

 of a solid of definite geometrical form, say a cylinder 

 or cube of brass, or glass, or quartz, of as perfect a 

 form as possible, and then to ascertain the weight, 

 referred to the prototype kilogramme, apparently lost 

 bv the solid when immersed in water. The two parts 

 of this operation are of very unequal difficulty : that 

 of ascertaining the dimensions is by far the more 

 difficult. Thanks to the admirable equipment of the 

 bureau, the hydrostatic weighings could be made with 

 a very high degree of accuracy. 



It is impossible within the space at disposal to enter 

 into the details of manipulation or to explain the 

 manner in which the experimental methods were car- 

 ried out. For information on these points the 

 memoirs themselves must be consulted. The final 

 results, obtained after a careful ' revision of all the 

 calculations, may be thus summarised : — 



Method of Contact. 



Mass of a Volume of a \v • >,» j 



cubic dc-i'i.etre kilogramme "^'Snted 

 of water of water ^^*^" 



kg- 

 0-9999749 



o 9999655 



0-9999672 



Bronze cylinder of 14 

 .. ,, 10 



dm^ 

 I 0000251"! 



1 -0000145 -I -000029 

 I -0000328 I 



Interferential Method by Reflexion. 

 cm. kg. dmS 



Cube of glass 4 09999713 10000287 



/ 1st measure 09999789 10000211 



" ^\2nd „ 0-9999784 I 0000216 



,, 5 reworked 0-9999731 1-00002691 



,( 6 0-9999696 10000304 



,, 5 0-9999731 I 0000269 j 



- 1 -C00026 



I •0000259') 



I -0000271 r°°°°^7 



Interferential Method by Transtnission 

 cm. kg. dm'* 



Cube of quartz 4 0'999974i 



5 09999729 



With respect to the relative value of the methods of 

 measurement, there can be little or no doubt in M. 

 Benoit's opinion that those obtained by the method 

 of optical interference are to be preferred to the 

 mechanical method of contact. On the other hand, 

 the older method has the advantage that bodies of 

 larger volume can be employed with a corresponding 

 diminution of error in other directions. The three 

 results are, it will be seen, very close together. The 

 final mean falls between 100027 and 100028, and is 

 rather nearer the first than the second number. 



.Accepting the sixth decimal as the limit of accuracy, 

 the ultimate result is that i kilogramme of pure water, 

 free from air, at 4°, and under normal pressure, 

 measures 1000027 cubic decimetre; or that the mass 

 of I cubic decimetre of this water is 0-999973 kilo- 

 gramme. 



The uncertainty of these numbers probably does not 

 exceed i in the last figure, or about a milligramme 

 on the kilogramine. 



M. Rene Benoit, the director of the bureau, con- 

 cludes the resume of the three important memoirs 

 which have led to this result which some general 

 observations on its bearing upon the question of the 

 relation of the actual value of the kilogramme to its 

 original theoretical definition. He justly points out 

 that the original standard kilogramme of Lefevre- 

 NO. 2147, VOL. 85] 



Gineau and Fabbroni was constructed with a perfec- 

 tion truly admirable, and altogether extraordinary 

 when one considers the general state of science and 

 the means at command in their epoch. Their kilo- 

 gramme was in effect represented by the mass of a 

 cube of water, the side of which measured not exactlv 

 I decimetre, but 1000009 decimetre. Even if it be 

 admitted that such a result could only have been 

 obtained by a fortunate compensation of errors, it is 

 certain that a like perfection can only be secured to- 

 day by obser\'ers equipped with all the resources of 

 modern metrology, working with the most scrupulous 

 care, joined to a critical faculty of the highest order 

 in the sifting and discussion of results. 



He points out that whilst it might be possible to 

 construct a new standard kilogramme in closer con- 

 formity with its definition, there would be little prac- 

 tical gain in so doing. The litre, the volume of a 

 kilogramme of water, is in practical conformity- with 

 the cubic decimetre, not only for the needs of ordinary- 

 life but for bv far the greater number of the require- 

 ments of science. Should any case need a higher 

 degree of precision, there would be no difficultv in 

 the application of a correction based upon the conclu- 

 sions of the present work of the bureau. M. Benoit 

 sees in the general result a proof of the wisdom of the 

 decision of the International Metric Commission of 

 1872, not to disturb the original standards, but in con- 

 stituting the international kilogramme as funda- 

 mental prototype simply to copy the old kilogramme of 

 Lefevre-Gineau and Fabbroni. 



T. E. Thorpe. 



NOTES. 



Prof. J. H. Poyntin-g, F.R.S., has been elected a 

 foreign Fellow of the Reale .Accademia dei Lincei. 



Bv the will of Mr. Thomas Lupton, solicitor to the 

 Royal Institution, the institution will receive io,oooZ. for 

 general purposes. 



M. .Armand G.^utier will be president of the Paris 

 .Academy of Sciences for 191 1. M. Lippmann has been 

 elected vice-president. 



It has been decided to establish a laboratory for re- 

 searches in the chemistry of therapeutics in the Pasteur 

 Institute in Paris. The laboratory will be directed by M. 

 Ernest Fourneau. 



On Thursday next, December 29, Prof. Silvanus P. 

 Thompson will commence the Christmas course of six 

 juvenile lectures at the Royal Institution on " Sound, 

 Musical and Non-musical." 



The Paris correspondent of the Times reports that Prof. 

 Guignard, who has acted as director of the Paris School 

 of Pharmacy for the last fifteen years, has resigned his 

 appointment, and is succeeded by M. Henry Gautier, 

 professor of mineral chemistry at the school. 



The Institution of Xaval Architects, which was founded 

 in i860, has received an intimation from the Lord Presi- 

 dent of the Priv\- Council to the effect that the King has 

 been pleased to approve of the grant to the institution of 

 a Royal Charter of Incorporation. 



A CORRESPOXDEXT of the Daily Chronicle states that a 

 brilliant display of aurora borealis was witnessed at 

 Hampstead on Monday, December 19, between 10.30 p.m. 

 and II p.m. The display started in the north-north-west, 

 and the streamers spread across the sky so far as the 

 constellation of Orion. 



