552 



NATURE 



[February 23, 191 1 



ton weight. A table of values of the coefficients is given 

 'for values of VV from 15 tons up to 75 tons. This formula 

 shows a maximum error of half of i per cent, when 

 •compared with the experimental results. .Another 

 empirical formula is given which has a maximum error 

 •of 95 per cent., viz. 



T> - S + 396-00.II W 

 4-08 + 0-152 W 

 The formulae are limited to conditions similar to those 

 ;prevailing during the trials, viz. straight and level track 

 of good construction, temperature above 30° F., wind 

 •velocity not more than 20 miles per hour. 



In our notice of the fourth edition of *' Les Roches et 

 leurs Elements min^ralogiques," by the late M. Ed. 

 Jannettaz, in December last (vol. Ixxxv., p. 166), we com- 

 plained of the description of the work as a revised and 

 ■enlarged edition (Quatrieme Edition, revue et augment^e). 

 We have now to acknowledge the receipt from the pub- 

 lishers, MM. Hermann et Fils, Paris, of another copy with 

 modified cover and title-page, in which it is now described 

 correctly as " Quatri^me Edition, conforme k la Troisi^me 

 et augment6e de huit planches." The publishers assure us 

 they had no intention of misleading purchasers by the 

 wording of the former description. The work has at least 

 *he merit of cheapness, the price being only eight francs. 



We have received from the Board of Agriculture and 

 Fisheries a memoir of the Geological Survey, Scotland, 

 •entitled " Catalogue of Photographs of Geological Sub- 

 jects," which has been prepared by the Geological Survey 

 and Museum. The catalogue enumerates the first 19 13 

 photographs taken to illustrate subjects of geological 

 interest in Scotland. The number, subject, and locality of 

 each photograph are given, and the number of the i-inch 

 map in which each locality occurs. The districts illustrated 

 lie chiefly in the north-west Highlands, Skye, in the 

 •counties of Argyll, Perth, Aberdeen, Kincardine, Fife, 

 Haddington, and Mid-Lothian. Copies of the catalogue, 

 price 6d., can be obtained from any agents for the sale of 

 Ordnance Survey maps, or- through any bookseller. 



OVR ASTRONOMICAL COLUMN. 



Nova Lacert^. — L'Astrononiie for February contains a 

 jiumber of observations of Nova Lacertae, and includes a 

 reproduction of a spectrogram secured by Dr. Mas Wolf, 

 at Heidelberg, on January 2. In addition to the broad 

 bright hydrogen lines, the outstanding features are the 

 band at X 463, several emission lines between Hj3 and 

 H7, a conspicuous break in the continuous spectrum on 

 the more refrangible side of H7, and the strong emission 

 . line near A. 4056. 



Nova Sagittarii, No. 3, H.V. 3306. — While examining 

 a plate taken at Arequipa on September 6, 1899, with the 

 i4nch Cooke lens, Miss Cannon found a star image which 

 appeared to be that of a nova in the position (1900) 

 R.A. =:i8h. 13m. 47-5S., dec. = -25° 13-5'; this is about 

 i' north of the C.D.M. tenth-magnitude star -25° 13020. 



The customary investigation of past plates revealed the 

 fact that the light-curve of the star had the characteristics 

 •of the curves of novae. A large number of photographs 

 were examined covering the period June 7, 1889, to 

 September 3, 19 10, and many of them showed no trace of 

 the nova. On plates taken on .August 5, 6, 7, and 9, 1899, 

 It is not shown, although the last-named shows a neigh- 

 bouring star of magnitude 11-4, yet the photograph of 

 August 10, 1899 (G.M.T. I2h. 28m.), shows it at full 

 brightness, viz. magnitude 8-5 ; this photograph was taken 

 with the 13-inch Boyden telescope, the exposure being 

 loom. Seven plates, taken for the cluster N.G.C. 6266, 

 show a star of magnitude 15-6 in the position of the nova, 

 within the limits of measurement, but this object exhibits 

 no variability on five earlier plates or on five plates taken 



NO. 2156, VOL. 85] 



since 1905. Since .August 10, 1899, the nova has appeared 

 on twenty-six plates taken with various instruments a; 

 Cambridge (Mass.), and Arequipa, and on the last <il 

 these, taken on October 3, 1901, its magnitude was 133. 

 The light-curve shows that the brightness decreased rapidls 

 at first, but was nearly stationarry, at magnitude 120, 

 from .April to July, 1900. A plate accompanying Circuhr 

 183 of the Harvard College Observatory reproduces t!. 

 photographs of the nova's region taken on August 3 aiv: 

 10, 1899. 



The Satellites of Mars. ^Observations of Phobos and 

 Deimos during the opposition of 1909 are recorded ij> 

 Prof. Lowell in No. 50 of the Lowell Observatory 

 Bulletins. Several interesting observations relating to tht 

 apparent magnitudes of the two satellites are described, 

 Phobos generally appearing the brighter. Thus on 

 September 16, 1909, it was half a magnitude brighter than 

 Deimos, although with reduced apertures — 6 inches being 

 the limit — it was the fainter. 



From a discussion of the data obtained. Prof. Lowell 

 finds that Phobos is probably 2-48 times the diameter of 

 Deimos, has 6-15 times the visible surface, and, if the 

 densities are equal, has 15-25 times the mass. The data 

 are too meagre to give a definite conclusion, but, so far 

 as they go, they suggest that there is a difference of 

 brilliancy in one, or both, of the satellites, dependent on 

 their orbital positions ; this suggests that each satellite 

 has different local albedoes, or an irregularity of shap . 

 and that it always keeps the same face towards Mars. 



The Spectra of some Wolf-Rayet Stars. — Bulletin 

 No. 182 of the Lick Observatory contains a note by Mr. 

 J. C. Duncan describing the spectra of seven Wolf-Royet 

 stars photographed by him, with the one-prism spectro- 

 graph mounted on the 36-inch refractor, during the summer 

 of 1908. 



Many of the lines and bands shown on these photo- 

 graphs exhibit no notable differences from those published 

 by Prof. Campbell in 1894, but those given in the follow- 

 ing table did not appear in the earlier publication : — 



A. of centre g^^j. g p Description of line or band 



of line or uand „ 



4I20'84 .. +35'3953 ... Narrow dark line 



4068-40 ... +30-3639 ... ,, bright,, 



4630 ... +36-3956 ... ,, faint band 



4058 ... +36-3987 ... Fairly bright band 15 A. U. wide 



4099 ... +363987 ••• M >. 34 ». 



4628 ... +36-3987 ... Faint bind 54 A. U. wide 



4056 ... +37'3»2i ... „ „ 



Southern Nebula. — Two notes describing remarkable 

 southern nebulae appear in No. 5 of the Transvaal 

 Observatory Circulars. 



The first deals with a great ring nebula in Aquarius 

 (N.G.C. 7293, Harding; 22h. 23m., -21° 26'), which is 

 nearlv circular and has a diameter of 11'. Mr. Innes 

 describes it as a remarkable object, looking like a ring 

 nebula superimposed on a planetary nebula, and states that 

 it was first seen in the 2-inch finder. This points to the 

 description " very faint " in the N.G.C. being incorrect, or 

 the nebula is variable ; it is difficult to account for its 

 being missed, with its present brightness, by Messier and 

 the Herschels. From a photograph taken on October 4, 

 1910, with 6om. exposure, Mr. .Woods describes the 

 nebula as a broad, continuous ring extending across 52s. 

 in R.A. and 12-6' in declination, and appearing slightly 

 fainter in 135° and 315° than at other parts. 



The second object was discovered on a plate taken by 

 Mr. Mitchell on August 1, 1910, with the Franklin-Adams 

 star camera, with an exposure of 2 hours. This is a 

 large, irregular nebula, around and preceding tt Scorpionis, 

 which is not mentioned in any of Dreyer's three cata- 

 logues. Its position is i5h. 53m., -25° 50', and it extend^ 

 over 1° in a north and south direction, its other diam'-: 

 being about i°. 



A Slowly Moving Meteor. — A fairly bright meteor, 

 remarkable for the leisurelv rate at which it moved, was 

 seen by Mr. F. E. Baxandall, at Putney, at 9 p^m. on 

 February 19. It first appeared in about 169°, +39°. ^nd. 

 travelling very slowly, passed through 211°, +28°, fi""'^^' 

 ; disappearing below the north-east horizon after a flig.it 

 i lasting fully 15 seconds. 



