December 17, 1908 j 



NA TURE 



195 



position of being the only nation having two repre- 

 sentatives on the committee. The circumstances lead- 

 ing to this are detailed in the " Proces-verbaux. " 

 The two members are Major MacMahon, F.R.S., and 

 Sir David Gill, K.C.B., F.R.S. 



One of the most important pieces of work recently 

 completed at the bureau is the new' study of the rela- 

 tion between the metre and the wave-length of the 

 red cadmium line. The classic research of Messrs. 

 Michelson and Benoit fifteen years ago laid the 

 foundation of a whole system of independent controls 

 on the invariability of the prototype. Although the 

 maximum divergence of the three independent deter- 

 minations made was only one micron (o-ooi mm.), 

 and the probable error of the mean considerably less, 

 yet it was felt desirable to repeat the work with 

 the highest possible refinements. This has been done 

 by Messrs. Benoit, Perot, and Fabry, employing a 

 totally different type of interference fringes from those 

 used in the earlier work. By this change and by 

 the use of "invar," the laborious "build-up" pro- 

 cess of the older method has been greatly shortened, 

 and the precision of the measurements much enhanced. 

 The results mav be stated as follows after all cor- 

 rections have been applied : — 



Mean of older determinations, 



I melre=l 553 164 'OjA,.. or A„ = 0;if643 S47 00 



New determinations, 



I metre=i 553 i64'i3A,; or A„ = o^'643 ^4^ 9^ 



the measurements being made in drv air at 15° C. 

 and under 760 mm. pressure. 



Among many other matters of interest in the 

 " Proces-verbaux " is an appreciation of the spectro- 

 scopist Thalen, formerly the representative of Sweden 

 on the International Committee, written bv his suc- 

 cessor, M. Hasselberg-. .After the application of 

 certain corrections, the author shows that the agree- 

 ment of Thalen's measurements of the wave-lengths 

 of the three principal cadmium rays with those of 

 Michelson is extraordinaril)' close. Rowland's values 

 are higher in each case by about one part in fifty 

 thousand. 



An appendix deals with the behaviour of nickel 

 steel standards of length. .According to the latest 

 investigations, a metre bar of the alloy invar, an- 

 nealed in the usual way at 40° C. for many hours, 

 gro-djs after this treatment, at first somewhat rapidly 

 for work of the highest precision — a micron in 100 

 days — and afterwards at a diminishing- rate. A curve 

 is given showing- that a bar which has been under 

 observation for 4000 days has not yet quite ceased 

 to change. During the whole period, however, its 

 change is less than fifteen microns. There is no need 

 to emphasise the enormous utility of invar for many 

 purposes, though this phenomenon would appear to 

 render it less suitable for absolute standards than 

 was once supposed. 



Passing now to the volume of the " Travnux et 

 Mumoires," we find the papers included in it are 

 six in number. Three of these relate to work done 

 some time ago by Dr. Chappuis before his departure 

 from Sevres, the first being an account of further 

 studies on the gas thermometer. This is followed bv 

 full descriptions of his now classic researches on the 

 dilatation of water and of mercurv. The first paper, 

 of sixty-six pages, deals with a repetition of the well- 

 known experiments which led to the adoption of the 

 hydrogen scale as the recognised international 

 --tandard of temperature over ordinary ranges. Using 

 both the original large reservoir of platinum-iridium 

 and one of hard glass, values were obtained for the 

 ( (ii'tTicient of expansion of hvdrogen under one metre 



NO. 2042, VOL. 79] 



initial pressure and at constant volume, substantially 

 identical with those found earlier. No perceptible 

 difference of " march " was found between the con- 

 stant-volume and constant-pressure hydrogen scales 

 between 0° and 100°. Many data are also given for 

 nitrogen and carbonic acid. 



.\n elaborate paper by M. Daniel Berthelot dis- 

 cusses the theory of the gas thermometer and llie 

 thermodynamic scale. It is proposed to deal with this 

 paper in a later article on thermometry. 



Other papers full of great practical interest deal 

 with the general methods of standardisation of divided 

 scales and of boxes of weights. These give, in a 

 summarised form, all the results of the unrivalled 

 experience of Messrs. Benoit and Guillaume and the 

 Sevres laboratory on these points. The remarks of 

 Dr. Benoit in the early pages of his paper on the 

 standardisation of weights should be studied by every 

 constructor of weights of precision. 



NOTES. 

 Sir J.AMES Dewar, F.R.S., has been elected an honorary 

 member of the German Chemical Society. 



Dk. F. W. Paw, F.R.S., consulting physician to Guy's 

 Hospital, has been awarded the Godard prize of 1000 francs 

 by the Paris Academy of Medicine, for his works on 

 carbohydrates and diabetes. 



Tub death is announced, at fifty-one years of age, of 

 Dr. Giuseppe Ciscato, professor of theoretical geodesy in 

 ilie University of Padua. 



A SPECIAL general meeting of the Geological Society 

 will be held on Wednesday, February 10, 1909, in order 

 to consider the result of the vote of the fellows on the 

 question of the admission of women into the society. 



We learn from Science that Prof. E. B. Poulton, F.R.S., 

 will give the annual, address before the Entomological 

 .Society of America at its Baltimore meeting on 

 December 31. The title of the address will be " Mimicry 

 in the Butterflies of North America." 



Dr. H. Breretox Baker, F.R.S., Lee's reader in 

 chemistry in the University of Oxford, will deliver the 

 Wilde lecture of the Manchester Literary and Philosophical 

 Society on March 9, the subject being " The Influence of 

 Moisture on the Combination of Gases." 



The Broca prize of 1500 francs for igoS has been 

 awarded by the Anthropological Society of Paris to Dr. 

 Paul Rivet. The prize was founded in 18S1 by Madame 

 Paul Broca, and is awarded for the best memoir on human 

 anatomy, comparative anatomy, or physiology in relation 

 to anthropology. The next award will be made in 1910. 



A MOVEMENT, supported by the Linnean Society of New 

 South Wales, is on foot to approach the Australian Govern- 

 ment with the object of having Barrow Island, sixty miles 

 off the north-west coast, set apart as a fauna reserve. 

 The island, which is remarkable for its kangaroo, bandi- 

 coot, rat, and wren, none of which occurs on the main- 

 land, is likely to be leased for sheep-farming, to the detri- 

 ment of the fauna. The wise policy of the Crown's reten- 

 tion of islands as sanctuaries for wild life is being amply 

 justified by the experiences of New Zealand and the United 

 States, and the Barrow Island fauna is worth effort to 

 save. 



The -Academy of Natural Sciences of Philadelphia has 

 appointed Dr. A. E. Brown as its delegate to the Uni- 

 versity of Cambridge Darwin memorial celebration. 



