Oct. 23, 1884] 



NA TURE 



613 



Kilogrammes 



International kilogramme Kl m s r - m s r - 



belonging to the Bureau 

 International kilogramme Kin 



belonging to the Bureau ... Kl — Kin= -0 I232±ooo26 

 Kilogramme-type C belonging 



to the Bureau C— Km= +o-32I7±oo334 



Kilogramme-type S belonging 



to the Bureau S— Km= +o-4632±<roo34 



Standard kilogramme H for 



Spain H— Km= - i-8762±o-oo34 



Standard kilogramme Z for 



Austria Z— Km= - i'35oi±o-oo34 



The present volume, like its two predecessors, is pub- 

 lished by the Director of the Bureau under the authority 

 of the Comite - , and contains some account of the modes 

 of comparison of the standards, with descriptions of the 

 apparatus used, and a complete statement of the observa- 

 tions and of the methods of their reduction. The work 

 of the Bureau has mainly included determinations of the 

 lengths of certain standard metres and of the weights of 

 certain standard kilogrammes for different Governments 

 and authorities, as shown in the above tables. 



These tables do not include the important compari- 

 sons of the British Standards with those of the Bureau, 

 an account of which is given in a Report presented to 

 Parliament by the Board of Trade last year, and in the 

 Report of the Proceedings of the Committee for 1883. 



The comparisons of the metres by Dr. Rene'-Benoit, 

 and those of the kilogrammes by M. Marek, were made 

 in the same manner and after the same methods as those 

 described in vols. i. and ii., to which we have previously 

 referred. 



M. Marek gives a thoughtful description of the excel- 

 lent normal barometer and cathetometer in use at the 

 Bureau, as well as of the methods of calibrating the ther- 

 mometers used during the weighings. There are also 

 illustrations of the apparatus used in ascertaining specific 

 gravities, and of M. Stas's method for clearing the sur- 

 faces of metals by a jet of alcohol vapour, of which we 

 regret that the demands on our space do not allow an 

 account. 



The many pages of observations and calculations which 

 are given in this volume are clearly arranged and care- 

 fully printed. We doubt, however, whether it may be 

 desirable to publish so much detail, particularly all the 

 observations of the balances. Each Report of verification 

 should evidently include all the observations, &c, from 

 which the results have been obtained, but it would appear 

 to be necessary only that the Government or authority 

 directly interested should be furnished with a full detailed 

 Report. Economy of time and money might be effected 

 to readers and purchasers, and perhaps the objects of the 

 Comite' further advanced, by the omission in such publi- 

 cations of any unnecessary detail. 



NOTES 



The Washington Prime Meridian Conference has adopted a 

 resolution declaring the universal day to be the mean solar day, 

 beginning, for all the world, at the moment of mean midnight 

 of the initial meridian, coinciding with the beginning of the 

 civil day, and that meridian to be counted from zero up to 

 twenty-four hours. The resolution further declares that the 

 Conference expresses the hope that, as soon as practicable, 

 astronomical and nautical days may be arranged everywhere to 

 begin at mean midnight. Prof. Janssen, of Fiance, moved that 

 the Conference should express the hope that technical investiga- 

 tions to regulate and extend the application of the decimal 

 system to the divisions of the circle and of time would be 

 resumed, in order to permit of the extending of that application 

 to all cases where it might present real advantages. The 



motion was adopted, and the Conference adjourned until 

 Wednesday. 



M. Bertrand, the Perpetual Secretary of the Pjris Academy 

 of Sciences in the Mathematical Section has been proposed as a 

 candidate to fill the place vacated by the death of M. Dumas in 

 the Academic Francaise. His nomination i^ certain, and will 

 take place without opposition. It is almost customary for the 

 Academie Franchise to offer a seat to one of the secretaries of 

 the Academy of Sciences ; Delambre, Fourier, Flouiens, Cuvier, 

 and Dumas enjoyed this honour in succession. Arago was 

 offered it several times, but obstinately refused it. He strictly 

 adhered to the old constitution of the In-tilut National as 

 created by the Directory of the First Republic, which slates 

 that the five sections constitute the several pails of a living 

 encyclopaedia established to deliberate in common on many dif- 

 ferent questions, and that consequently no member of one sec- 

 tion should be eligible to another. When the Restoration took 

 place, the Institul was divided into independent academies, and 

 the old practice of electing a person to several of them was 

 revived. It has not been altered since 1848, although several 

 attempts have been made in order to recall into existence the 

 former republican organisation. 



On the night of Saturday, October 4, some interesting obser- 

 vations of lunar coronas and fog-bows were made at Ben Nevis 

 Observatory. The mountain-top had been enveloped in mist 

 for several days previously, but about 9 p.m. it began to clear, 

 and by 11 o'clock the moon, partially eclipsed, was visible, sur- 

 rounded by a strong double corona ; all the colours from red to 

 blue being seen in both rings. Measurements of these were 

 taken by Mr. Dickson, Interim-Superintendent, with an instru- 

 ment designed for the purpose by Prof. Tait. These gave : — 

 Outer diameter of red — outer ring, 7 46' ; inner ring, 4 52'. 

 After midnight the sky became quite clear and the moon shone 

 brightly, no corona being visible. At times, however, detached 

 portions of very thin mist came up the north-west side of the 

 mountain and brushed over the top. Whenever this occurred a 

 strong corona again surrounded the moon, with a third set of 

 rings, outside the other two, and much fainter, bat sufficiently 

 bright to allow of all the colours being distinguished. At 1.30 

 a.m. on October 5 the outer set of rings was more distinctly 

 marked than before, and measurements were again taken. These 

 gave : — Outer diameter of red — inner ring, 4° 6' ; middle ring, 

 6° 2' ; outer ring, 8° 10'. All these measurements are subject to 

 an error of not more than ±6'. At 1.15 a.m. a lunar fog-bow 

 was visible on a fog bank to the northwards. From the edge of 

 the precipice to north-north-east of the Observatory this appeared 

 to consist of an outer ring, having a diameter of 75°, and an 

 inner and fainter ring, diameter 65°, the space between the rings 

 appearing almost quite dark, as if caused by a sharply-defined 

 break in the fog. No colours could be distinguished. 



From the Alta California we learn that the Lick Trustees 

 have just received, through the kindness of Capt. Goodall, of 

 the firm of Goodall, Perkins, and Co., important advices from 

 Paris in regard to the glass disk which is needed to complete the 

 36-inch equatorial for the Lick Observatory. It will be remem- 

 bered that the contract for two disks— one of flint and the other 

 of crown glass — which are needed for the construction of an 

 achromatic objective, was let to the celebrated firm of Alvan 

 Clark and Sons in 1S61. There were only two firms in the 

 world who were capable of making glass disks of such size, nearly 

 40 inches in diameter. The Clarks employed one of these, 

 Messrs. E. Feil and Co. of Paris, to cast the rough disks for 

 them. The flint disk was cast in an unexpectedly short time, but 

 the making of the crown glass disk has proved to be a matter of 

 great difficulty, and this alone will have delayed the making of 

 the large objective, and thus the completion of the Lick Obser- 



