Nov. 19, 1 8 74 J 



NATURE 



55 



surface for rcccivinq; the defining lines maybe given to 

 every one of the new metres. 



The apparatus for cutting the lines is connected with 

 the new longitudinal comparing npoaratus, carrying a mi- 

 croscope with its micrometer. The microscope is o'S m. 

 in length and magnifies more than 200 times ; and the 

 whole apparatus is placed in the cold chamber, which has 

 been constructed at the Consctvaloire des Aits ct Metiers, 

 and can be maintained constant at the normal temperature 

 ofo'^ C. The polishing of the bars, as w. 11 as the cutting 

 of the defining lines, the position of which must necessarily 

 be the result of the most precise comparisons with the 

 primary standard metre, are both entrusted to M. Tresca 

 and his son, M. Gustave Tresca. 



The lines are to be cut with a diamond point. Each 

 transverse defining line will be crossed at right angles by 

 two longitudinal lines o'l mm. apart, and the portion of 

 the transverse line so intercepted between the two lines 

 will define the length of the metre. The width of these 

 lines will probably be about 0002, or at most o'oo3 mm., 

 or 3 microns f/x^. This will be about one-fouith of the 

 thickness of tlie defining lines of our standard yards, 

 which are cut with a steel knife upon the polished surface 

 of a gold stud, and are viewed through microscopes 

 magnifying about si.\ty time?. 



Great progress has been made in the construction of 

 the series of new thermometer?, two of which are to 

 accompany each international staiidard metre. These 

 thermometers are being constructed by M. Baudm. Their 

 length is 045 m., and their external diameter 5 mm. The 

 bulbs have the same external diameter, and the two ther- 

 mometers can thus be placed m the groove of the X metre 

 bar for determining the temperature of its measuring 

 axis during comparisons under the microscopes. The 

 scale of the thermometers ranges from - 5 to + 50° C, 

 and each degree is subdivided into tenths. Every l"' 

 corresponds with a length of about 7 mm. Four standard 

 thermometers h.ave been constructed for the purpose of 

 verifying the new metre thermometers. They have an 

 arbitrary scale from 0° to 100" C, graduated in ball-milli- 

 metres by hydrofluoric acid on the glass tubes, and the 

 I'alue of the several graduations has been accurately de- 

 termined by calibmtion. The length of these standard 

 thermometers somewhat exceeds 050 m. 



The construction of the new international kilogrammes 

 and of the standard melrcs-a-lion/s will be deferred until 

 the completion of the number of inctres-a-traits required. 

 Meanwhile, several balances of the greatest precision 

 have been obtained for the weighings, some of which are 

 fitted with mirrors for observing the extent of the oscilla- 

 tions through .a telescope by means of a vertical graduated 

 scale fi.xed to the telescope and reflected in the mirror, 

 according to the principle adopttd by Gauss for observing 

 variations of the magnetic needle. 



For ascertaining the atmospheric pressure during the 

 weighings, the standard barometer of the Conservatoire 

 des Arts et Metiers, constructed by Fastre, is proposed to 

 be used, by which the height of the mercury can be read 

 to o'oi mm. An ingenious apparatus has been constructed 

 by M. Mendeleef, which shows the slightest variation of 

 pressure during the process of weighing, by means of a 

 small U-tube containing oil of petroleum. One end of 

 this tube is closed and contains a certain volume of dry air 

 maintained at a constant temperature, whilst the other 

 end is open to the air. The instrument being accurately 

 adjusted by means of a mercurial plunger connected with 

 the bottom of the U-tube, so that the petroleum is exactly 

 on a level on the two branches of the tube, it is found to 

 be so extremely sensible that the slightest variation of 

 atmospheric pressure is shown by an alteration of the 

 level, and the amount of this alteration can be measured 

 with the greatest precision. 



It is expected that the whole series of new meties-a- 

 traits will be completed by the French Section and ready 



to be handed over to the Comite Permanent by October 

 1S75, ^"d ^h'^' "^c construction of the new kiiogrammts 

 and metres-a- bouts will also be far advanced by that date. 

 During their late meeting, the question of the convoca- 

 tion of a Diplomatic Conference at Paris with the vii_vv of 

 providing the requisite means for enabling the committee 

 to er.ecute all the definite com|).arisons of the new metric 

 standards, and for securing the due preservation of the ncv.- 

 international metre prototypes and regulating their use 

 for future comparisons, was further considered by the 

 Committee. In pursuance of their resolution of last ye^r 

 upon this subject, the requisite communications were made 

 by the French Government to the Governments of the 

 several countries interested, and the Committee have now 

 passed a resolution that considering the numbers of Govern- 

 ments who have agreed to take part in such conference, 

 the French Government be requested to convoke it with 

 as little delay as possible. Information has been received 

 of the willingness of the French Government to accede to 

 the request, and the Conference wdl probably be held in 

 the spring of next year. H. W. Chisholm 



NOTES 



It is with the greatest pleasure and with samething like a 

 sense of relief that we are able at last to announce definitely that 

 at a Cab:net Council held last .Saturday it was decided that there 

 should be an Arctic Expedition, at the expense of Government, 

 to sail next spring. The welcome intelligence was thus an- 

 noimced by Mr. Disraeli to ( Sir Henry Rawlinson : — " Her 

 Majesty's Government have had under consideration the represen- 

 tations made by you on behalf of the Council of the Royal Geo- 

 graphical Society, the Council of the Royal Society, the Britisli 

 Association, and other eminent scientific bodies, in favour of a 

 renewed expedition, under conduct of Government, to explore the 

 region of the Xorth Pole, and I have the honour to inform yoa 

 that, having carefully weighed the reasons set forth in support of 

 such an expeduion, the scientific advantages to be derived from 

 it, its chances of success, as well as the importance of encouraging 

 that spirit of maritime enteqjrise which has ever distingiiisheil 

 the English people, her Majesty's Government have determined 

 to lose no time in organising a suitable expedition for the 

 purposes in view." Steps have, we believe, been already taken 

 to carry into effect this resolution, which reflects so much credit 

 on her M.ajesty's Government. Admiral M'Clintock left for 

 Dundee on Tuesday with an engineer and shipwright, to buy two 

 steam whalers, which wdl be fitted out under the tried explorer's 

 superintendence at Portsmouth. Capt. A. H. Markham, who 

 went to Baffin's Pay last year, will probably occupy an important 

 post in the expedition, the route of which will, of course, be 

 Smith's Sound. Now that the thing has been decided on, there 

 is no doubt that it will be thoroughly well done ; and now that 

 Englishmen have once more got the chance, we may expect 

 something like real work, if, indeed, they do not take the last 

 step in the solution of the Arctic mystery. 



ViE take the following from the Tinus : — The medals in the 

 g'ft of the Royal Society for the present year have been awarde.ls 

 by the Council as follows, and will be presented at the anniver- 

 sary meeting on the 30th inst. : — The Copley Medal to Prof. 

 Lnuis Pasteur, of the Academy of Science, Paris, For. Mem. 

 R. S., for his researches on Fermentation and on Pebrine. The 

 Rumford Medal to Mr. J. Norman Lockyer, F.R. S., for his 

 spectroscopic researches on the sun and on the chemical ele- 

 ments. A Royal Medal to Prof. William Crawford Williamson, 

 F.R.S., of Owens College, Manchester, for his contributions to 

 zoology and palceontol'jgy, and especially for his investigations 

 into the structure of the fossil plants of the coal-measures ; and 

 a Royal. Medal to Mr. Henry Clifton Sorby, F.R.S., for his 



