August io, ign] 



NATURE 



19; 



— in separate rooms, if possible — for grinding and polish- 

 ing, respectively, is to be advocated. 



Two years ago it was shown by Ramsay and Usher 

 that a solution of thorium nitrate, left to itself for some 

 months, gave off a certain quantity of carbon dioxide, and 

 that under the action of the radium emanation the thorium 

 solution gave off this gas much more rapidly. The view 

 was put forward that the carbon of the carbon dioxide 

 might have been produced during a transformation of the 

 atoms of thorium by the action of the radium emanation. 

 In the Comptes rendus of the Paris Academy of Sciences 

 for July 24 M. Herschfinkel gives a description of a 

 repetition of these experiments. The production of a 

 trace of carbon dioxide by the solution of thorium nitrate 

 left to itself, and the increase of this amount under the 

 influence of the radium emanation, were confirmed. It 

 was, however, found that oxidation of the thorium nitrate 

 R-ith a solution of potassium permanganate also gave rise 

 to the production of carbon dioxide, and this in spite of 

 the great care taken in preparing a pure salt. The con- 

 clusion is drawn that the appearance of carbon dioxide 

 under the conditions of this experiment cannot be taken 

 as any evidence of the production of carbon from atomic 

 transformation of the thorium. 



An article on scientific management and efficiency in the 

 United States Navy, by Walter B. Tardy, appears in The 

 Engineering Magazine for July. Less than 3 per cent, of 

 all the shells fired in the battle of Santiago by the 

 American fleet hit the enemy. There is no record that a 

 single 12-inch or 13-inch shell took effect. The ranges 

 were less than 3000 yards. Recently the New Hampshire 

 used the old Texas as a target, firing at ranges from 

 10,000 to 11,500 yards, and landed whole salvos on the 

 Texas whenever she wished. The Michigan, an all-big- 

 gun ship, recently made twenty-two 12-inch hits at ranges 

 of 10,000 yards while steaming at 15 knots, the target 

 being only 60 feet long by 30 feet high. She fired forty- 

 eight 12-inch shells, the percentage of hits being about 45 ; 

 the shots were fired at the rate of about two per minute 

 per gun. Organisation and strict attention to details are 

 responsible primarily for the great improvement shown. 

 Among other matters, coaling has received considerable 

 attention, and the rate has been improved from 30 or 40 

 tons per hour to 200 tons per hour for the entire coaling 

 period ; some ships have taken on and trimmed as much 

 as 350 tons per hour for the entire coaling period, with a 

 record of about 550 tons for the best hour. 



OUR ASTRONOMICAL COLUMN. 



Rediscovery of Encke's Comet, 191 id. — A telegram 

 from the Kiel Centralstelle announces that Encke's comet 

 was discovered by Dr. Gonnessiat at the Algiers Observa- 

 tory on July 31. Its position at 15b. 54.5m. (Algiers 

 M.T.) was R.A. =7h. 27m. 54-55., dec. = 26° 54' 6" N., 

 and its brightness was estimated as being about equal to 

 the tenth magnitude ; this position lies in Gemini very 

 little south of Castor and Pollux. 



Owing to its faintness and unfavourable position, it was 

 not expected that this famous comet would be easily 

 detected at this return ; only under the most favourable 

 conditions has it ever become a naked-eye object. The 

 comet is famous as being the first short-period (3-3 years) 

 comet for which the periodicity was established, and also 

 for its very slow but persistent acceleration, which was 

 held to be a demonstration of the existence of a 

 luminiferous aether. According to M. Bosler and others, 

 its brightness varies with the sun-spot activity through the 

 eleven-year period. 



NO. 2l8o, VOL. 87] 



Stellar Parallaxes. — Dr. Schlesinger's discussion and 

 summary of his parallax results obtained with the Yerkes 

 40-inch refractor — the seventh paper of the series — appears 

 in No. 1, vol. xxxiv., of The Astrophysical Journal; only 

 a few of the more interesting points can be noticed here. 

 The results for four helium stars included in the pro- 

 gramme confirms the proper-motion results in pointing to 

 the fact that this class of stars is situated at an enormous 

 distance from the earth, so much so that, taking averages, 

 a fourth-magnitude helium star is probably as distant as 

 the ninth-magnitude stars in the same region of the sky. 

 Of these four, three give negative and one slightly positive 

 parallaxes ; no other star measured gave a negative value. 



A practical point elucidated is that with such an instru- 

 ment as the Yerkes telescope the number of parallaxes that 

 may be determined per annum, with an average probable 

 error of +0-013", is about the same as the number of fine 

 nights. 



Of the twenty-six stars given in the tabular summary, 

 three, Groombridge 34, P.M. 2164, and Kriiger 60, have 

 parallaxes greater than 0-2" ; the mean values for these 

 three are 0-266", 0-282", and 0-252" respectively. 



During the minute examination of sources of error it 

 was shown that measuring the plates in duplicate adds 

 only 10 per cent, to their weights; such measurenv :nts 

 were early discontinued. In some cases a rotating disc 

 was employed to reduce the brightness of the parallax 

 star, and the final probable errors show that no increased 

 error was thereby produced. 



Prominences in 1909. — Prof. Ricco's valuable summarv 

 of the Catania prominence observations for 1909 appears 

 in No. 6, vol. xl., of the Memorie di Astmfisica ed Astro- 

 notnia (June, p. 83). Compared with iqoS, especially with 

 the latter part of that year, the frequency and dimensions 

 of the prominences showed an increase in iqoq. Slight 

 differences are seen in the mean latitudes, and the maxi- 

 mum frequencies — in io° zones — occurred in 20 — 29 N. 

 and the 3o°~39° S. latitudes. This was the only maximum 

 in the southern hemisphere, but in the northern there was 

 a minor maximum in the zone 5o°-5q° N. The mean daily 

 frequencies were 1-84 for the northern and i-8i for the 

 southern hemisphere, while the respective me;,n helio- 

 graphic latitudes were 31-9° N. and 27-5° S. On 8 per 

 cent, of the days of observation no prominences were seen 

 during the first half of the year, while only two days 

 (2 per cent.) yielded no prominences during the second 

 half. 



The Algol System RT Persei.— Contribution No. 1 

 from the Princeton University Observatory is a mono- 

 graph, by Mr. R. S. Dugan, dealing with the observa- 

 tions of the Algol variable RT Persei made at the Halsted 

 Observatory with the 23-inch telescope during 1905-8. 

 After describing and discussing the observations, Mr. 

 Dugan concludes that there is undoubtedly a secondary 

 eclipse, that the two stars are practically equal in size, 

 and that the reality of the light-changes between eclipse? 

 is fully guaranteed by the probable error. 



Jupiter's Faint Satellites. — Observations of the fainter 

 satellites of Jupiter are being kept up at the Transvaar 

 Observatory. Four good exposures were made during" 

 April and May, but on one plate only is J viii to be 

 found. Images of J vi appear on all the plates, and it is 

 estimated that this object is at least two magnitudes 

 brighter than J viii. The places given as yet are not final, 

 but, brought up to the equinox of date, they show good 

 agreement with those given by Dr. Crommelin's ephemeris. 

 Observations of twelve minor planets, five of which are 

 suspected to be new, were made during the satellite 

 observations ; temporarily the new ones have been desig- 

 nated T,-T,, and their positions are given with the above 

 in Circular No. 8 of the Transvaal Observatory. 



The Brightness of Comets iqo8 III. and 1910a. — The 

 variations in the brightness of Morehouse's comet and in 

 that of comet 1910a have been investigated in detail by 

 M. Orlow, who publishes the results in No. 4513 of the 

 Astronomische Nachrichten. Eliminating the terrestrial 

 distance, he finds confirmation of the result that a cornet's 

 brightness varies more than is expressed by the formula 

 i/r 2 A 2 . The ratio i/A 2 /*- 1 is nearer the observed results, 

 the index of r in the case of comet 1910a being 46. 



