November 3, 1892J 



NATURE 



21 



gaged did not know that air is heavier than steam. One might 

 as well say one's grocer did not know sand from sugar. 



The Jackets Committee has not yet concluded its labours, and 

 another report will be forthcoming in due course. Mr. Aspinall 

 has offered a locomotive for trial, and we heard that Mr. Yarrow 

 will put a torpedo boat at the disposal of the committee, and 

 has even promised to cast special cylinders for experimental pur- 

 poses. The locomotive will afford an interesting field of research, 

 running as it does so largely linked up. The torpedo boat 

 experiments will be no less interesting, especially in view of the 

 great number of revolutions the engines of these craft make in a 

 given time. 



On the second day of the meeting the paper by Mr. Walker 

 of Bristol on the screw propeller. This paper gives the details 

 of some experiments made by the author on a form of screw 

 propeller invented by the late Mr. B. Dickinson. It would be 

 in vain for us to attempt to condense this paper within the 

 limits at our disposal. With regard to the merits of the 

 Dickinson propeller we have nothing to say. It consists 

 essentially of two narrow blades in place of one, and reminds 

 us strongly of a Mangin propeller with one blade set somewhat 

 back on the shaft. Mr. Walker contends that his researches 

 prove the advantages of long narrow blades, but he did not 

 appear to have converted the high authorities present, including 

 Mr. Froude, Mr. Thorneycroft, and Mr. Barnaby — the three 

 best-known names in connection with the subject — to his views. 

 It is difficult to see wherein the value of the paper exists. Prof. 

 Kennedy in the discussion stated that the generally received 

 opinion as to the increase of the friction of the load was 

 erroneous, and that the power absorbed in this way does not 

 increase in the manner stated, a fact which he illustrated by 

 means of a diagram. Mr. Thorneycroft pointed out that "life 

 was not long enough " for the larger trials proposed by the author, 

 but that he might decide one point if he would confine himself 

 to models. Mr. Barnaby stated that a broad-bladed propeller 

 should not be a uniform pitch. Mr. Froude's speech was a lucid 

 criticism of the author's paper, the speaker pointing out in a 

 kindly but convincing manner that the conclusions arrived at 

 by the author might be subject to revision. Mr. Dunell, 

 whose previous experiments the author had quoted, added to 

 the information given by putting forward some other experiments 

 he had made upon screw propellers fitted to a torpedo boat, in 

 this case the results being opposed to those claimed by the 

 author, inasmuch as the shorter and broader blade had proved 

 the more advantageous. Mr. Shield, of Liverpool, described a 

 form of propeller which has been in use on the Mersey, and 

 appears to offer some advantages. The blades are attached to 

 the boss in two parts, and are joined in a loop at the top. 

 According to Mr. Shield's statement, the arrangement gives 

 great advantages in towing, and also increased steadiness in 

 running. The latter we can accept as a fact, but the great 

 increase in towing capacity seems almost too good to be 

 accepted literally. Twenty-five per cent, additional efficiency 

 is a very large gain without further expenditure than an 

 exchange of screws ; but this is what the propeller in question 

 is said to realize. 



The meeting concluded with the usual votes of thanks. 



INTERNATIONAL COMMITTEE OF WEIGHTS 

 AND MEASURES. 



'pHE InternationalCommittee of Weights and Measures, which 

 was established in consequence of the Metric Convention 

 of 1873, has recently issued its fifteenth annual report to the 

 Governments represented at that Convention.^ The committee 

 have also lately published the minutes of their proceedings 

 (Proces-Verbaux des Seances. Paris, 1892. i vol. 8vo) at 

 the annual meeting held at Paris in September, 1891. It appears 

 to be hardly possible that the proceedings of the committee at 

 their meeting which was held last month may be issued before 

 next year, but from the above publications, as well as from a 

 recent volume of their " Travaux et Mcmoires," we gather that 

 they continue to carry on their investigations with all despatch. 

 In their last report the committee deplore the death of their 

 colleague, JeanServais Stas, whose analyses of the platinum 

 alloys have, together with those of St. Claire Deville and George 



1 Rapport du Comit<5 International. Gauthier-Villars. Paris, i Vol. 

 50 pp., 1892. 



NO. 



I 201, VOL. 47] 



Matthey, so largely helped forward the principal work of the 

 committee ; the metallurgical studies of Stas are indeed recog- 

 nized as veritable models of classical research in this particular 

 field. 



The new instruments added to the Bureau at Sevres during 

 the last year include a normal barometer (le Barometre Fuess) 

 and manometer, originally verified for reference as an inter- 

 national standard in accordance with the decisions of the 

 Meteorological Conferences, particularly that at Munich last 

 year. The committee have also obtained a new apparatus for 

 determining the normal thermometric "boiling point," or the 

 temperature of 100° Centigrade, as it has been found that the 

 form of apparatus used by Regnault was unreliable for this pur- 

 pose. In the reading of the standard manomtter it would ap- 

 pear that higher accuracy has been obtained by raising the 

 surface of the mercury up to a fixed point, the image of the 

 point in the mercury being observed at the same time by means 

 of a microscope. The Wild-Pernet barometer has been re- 

 mounted, and the Bureau are now prepared to undertake the 

 verification of any standard barometer. 



The readings of all mercurial thermometers are given at the 

 Bureau in terms of the hydrogen thermometer ; and a 30- 

 litre holder for methyl chloride, or liquid carbonic acid, has been 

 made by Brigonnet and Navile. The low temperature experi- 

 ments have been continued by M. Chappuis down to —75° Cent. ; 

 and toluol and alcohol thermometers have been compared with 

 the hydrogen thermometer. It has been found that " toluol " is 

 more sensitive and reliable for low temperatures than alcohol. 



We note that the meteorological work of the committee has 

 largely developed itself; and that, as in geodetic research, 

 the Bureau at Sevres is now recognized as a central and inter- 

 national station of reference. Standard thermometers have 

 been verified, for instance during 1892, for the Governments of 

 Russia, France, and Roumania ; for the Universities of Rome, 

 St. Petersburg, and Odessa ; for Owens College, Manchester ; 

 and for several recognized meteorological observatories. Great 

 Britain has also been supplied by the committee with standard 

 thermometers similar to those supplied to other contracting 

 States. ^ 



Besides the standard metre and kilogramme already delivered 

 to this country, the Bureau is undertaking the construction of a 

 further standard metre for the Board of Trade, at a cost of 

 12,588 francs. The new standard appears to have been nearly 

 two years in construction, but its verification is now promised 

 this year. 



There are twenty-one different governments who have joined 

 the Convention and who contribute annually towards the 

 expenses of the Bureau (the annual budget of which is 75,000 

 francs), sums varying from 134 francs (Denmark) to 9482 francs 

 (Germany) the annual contribution of Great Britain and Ireland 

 for 1892 being stated at 4699 francs, or nearly ;i^i88 ; and that 

 of the United States at 8471 francs. 



At the instance of Dr. B. A. Gould the committee are now also 

 undertaking an inquiry affecting measurement by light waves. 

 By the use of the " Refractometer " Dr. Michelson found 

 {Philosophical Magazine, April, 1891, and September, 1892) 

 that accuracy of measurement by light- waves may be increased 

 to a high degree of accuracy. By the best spectroscopic instru- 

 ments now in use it has been stated to be difficult to "resolve" 

 lines as close together as the components of the yellow sodium 

 lines, but that if the width of the lines themselves be less than 

 their distances apart, then there is no limit to their accuracy of 

 measurement by the " Refractometer." We shall look forward 

 with interest to the publication of Dr. Michelson's further results, 

 in the next volume of the "Travaux et Memoires " of this 

 committee. 



The new instrument designed by M. Gustave Tresca, of the 

 Conservatoire des Arts eft Metiers at Paris, for the adjustment 

 and polishing of the terminal surfaces of end-measures of length 

 appears also to be better than anything yet adopted in England. 



The committee not only undertakes the verification of stan- 

 dards and instruments for the High Contracting Governments 

 (who have the right to demand such verifications), but they also 

 verify for any scientific authorities or persons. To those of our 

 readers, therefore, who may desire to have standards or instru- 

 ments verified by the committee, the following information may 

 be useful : — 



Applications for the verification of instruments should first be 

 made to M. le Direcieur du Bureau International (Dr. Rene- 

 Benoit), au Pavilion de Breteuil, Sevres, pres de Paris. 



