October ig, 191 1] 



NATURE 



529 



Messrs. H. F. Angus and Co., of Wigmore Street, 

 London, W., have issued their second catalogue of second- 

 hand scientific apparatus and accessories. All the instru- 

 ments listed have been tested, adjusted where necessary, 

 and, unless otherwise stated, are capable of work of equal 

 precision as when new. The catalogue gives particulars 

 of microscopes and accessories, various other optical instru- 

 ments, and sundry apparatus. 



The second part of vol. iv. of the Proceedings of the 

 University of Durham Philosophical Society can now be 

 obtained from Messrs. A. Reid and Co., Ltd., of Newcastle- 

 upon-Tyne. It includes a selection of the papers read to 

 the society between December 8, 1910, and May n, 191 1. 

 These papers include a description of a new steam trap, by 

 Mr. E. M. Eden ; one by Prof. Henry Louis on the mutual 

 development of metallurgy and engineering ; and others by 

 Dr. T. H. Havelock, on the displacement of the particles 

 in a case of fluid motion ; by Dr. J. A. Smythe, on benzyl- 

 orthothioformate ; and by Dr. A. A. Hall, on the relation- 

 ship between the chemical composition and the position of 

 some North Country clays. In addition there is a report 

 of the Boulders Committee on the boulders and pebbles 

 collected or determined since the last report of the com- 

 mittee. 



Erratum. — In line 9 of Mr. Rollo Appleyard's letter in 

 Nature of October 12, for A=e read A = e u . The ex- 

 pression was correctly given by Mr. Appleyard in his letter, 

 and the r wa= in place in the page passed for press, but it 

 fell out in the course of printing last week's issue. 



OUR ASTRONOMICAL COLUMN. 



Changes on Mars. — An observation made by M. Jarry 

 Desloges at the Massegros Observatory, and published in 

 Circular No. 133 from the Kiel Centralstelle, records a 

 change on the Martian feature Libya. Previous observa- 

 tions had shown this area to be of a dull greyish hue, but 

 on October 12 it was seen to be very bright ; changes in 

 the intensity of these white areas are by no means un- 

 common, and Libya, for example, was recorded as intensely 

 white by the Rev. T. E. R. Phillips on May 22, 1903. 



Colour Photograph? of Mars. — In No. 42 of the 

 Mitteilungen der Nikolai-Hauptstemwarte zu Pulkowo M. 

 Tikhoff describes some results he has secured by taking 

 photographs of Mars through coloured screens. These 

 screens transmitted light of wave-lengths 690-655 mm (red), 

 6S0-600 MM (red and orange), 620-545 W (orange and 

 yellow) and 550-495 MM (g r een), respectively, and were 

 used in conjunction with the 30-inch equatorial telescope. 

 Taken at the focus, the images of Mars were about 1-5 mm. 

 diameter. 



Excellent photographs of Mars were secured, and a com- 

 parison of those taken with the red and with the green 

 filters shows some remarkable differences. For example, 

 on the " red " photographs the " continents " (Hellas, 

 Elysium, Ausonia, &c.) are very bright, much brighter than 

 the south polar cap ; the latter is the most intense feature 

 on the " green " photographs. 



The seas are very dark on the " red " plates and greyish 

 on the " green " ; the canals (such as Xanthus, Scamander, 

 Cerberus, &c.) are best seen on the " red " and " orange- 

 red " photographs, their colour apparently resembling that 

 of the seas. 



The study of the polar cap led to the conclusion that it 

 was of a greenish colour rather than white, and this sug- 

 gested ice rather than snow, so experiments on the absorp- 

 tion spectrum of ice were carried out. These, and photo- 

 graphic experiments on sand, snow, and ice made by M. 

 Kalitine, confirmed the conclusion that during August 4-30, 

 1909, the south polar cap of Mars exhibited the optical 

 properties of ice rather than of snow. 



NO. 219O, VOL. 87] 



Brooks's Comet, 1911c. — Below we give a further 

 extract from the ephemeris for comet 1911c, published by 

 Dr. Ebell in No. 4528 of the Astronomische Nachrichten. 

 The cloudy and hazy skies of the past week have rendered 

 observations difficult, and, apart from these local condi- 

 tions, the difficulty will now increase owing to the 

 decreasing northerly declination and magnitude. 



Ephemeris 12/1. M.T. Berlin. 

 1911 a (true) 8 (true) log r log A mag. 



Oct. 19... 12439 ••• +18 1 5*5 ... 97241 ... 9S498 ... 2-8 



,, 21 ... 12 397 ... +15 13-1 



,, 23 ... 12 36-5 ... +12 I0'4 ... 97OOO ... 9 - 88SO .... 2-9- 



„ 25 ... 12 34-4 ... + 9 S-S 



,, 27 ... 12 33-3 ... + 6 9-6 ... 9-6904 ... 9-9219 ... 3-0 



„ 29 ... 12 33-2 ... + 3 14-3 



„ 31 ... 12 33-9 ... + O 24-0 ... 9-6978 ... 9-9587 ... 3-2 

 Nov. 2 ... 12 35-5 ... - 2 2O'0 



This path lies nearly due south through Coma and Virgo, 

 and the comet will be quite near to 7 Virginis on 

 November 1. 



The Solar Eclipse of April 17, 1912. — From the 

 Gazette Astronomique (Nos. 45-46) we learn that prepara- 

 tions are to be made by the Uccle Observatory to organise 

 two stations for the observation of the solar eclipse of 

 April next. According to the Connaissance des Temps 

 data, the eclipse should be total for six seconds in Spain, 

 for two seconds in the neighbourhood north of Paris, and 

 should cease to be total in Belgium. But the Nautical 

 Almanac data would make it not a total eclipse anywhere 

 in Europe, although the greatest duration of annular 

 eclipse, six seconds, would then take place in Belgium. 



An Enormous Bolide.— On April 10 a great noise was 

 heard at Catania following, by about three minutes, a 

 brilliant flash of bluish-green light ; the microseismograph 

 also registered slight movements. These phenomena and 

 their relation to a bolide are discussed very fully by Prof. 

 Ricco in No. 7, vol. xl., of the Memorie di Astrofisica ed 

 Astronomia, who finds that the meteor probably exploded 

 at a height of 30 km. above a point some 52 km. N.N.E. 

 of Catania. A careful search in the indicated region has, 

 however, revealed no traces of the fragments as yet. From 

 file tabulated summary of communicated observations it 

 would appear that a most extraordinary phenomenon was 

 very generally observed. 



Micrometer Measures of Engelhardt-Siumpe Stars. — 

 During the winter of 1910-11 Dr. Lau employed the 10-inch 

 refractor of the Urania Observatory for micrometer 

 measures of faint stars measured by Engelhardt in the 

 neighbourhood of stars given in Stumpe's catalogue. From 

 these measures and Engelhardt's he has derived the proper 

 motions, which he now publishes in No. 4523 of the Astro- 

 nomische Nachrichten, with notes as to the colour and 

 magnitudes of the pairs ; of the fifty-four systems given, 

 about two-thirds are optical, and one-third physical, 

 systems. 



Photographs of the 1898 Total Solar Eclipse. — From 

 the Tokio Observatory we have received a copy of the 

 report of their 1898 eclipse observations, published in 1910. 

 The volume contains some excellent reproductions of photo- 

 graphs of the corona, which were taken at Jeur, in 

 western India, and are described and discussed by Mr. H. 

 Terao and Prof. S. Hirayama. 



Cooperation in Observing Variable Stars. — The 

 observation of variable stars is one that calls for only a 

 modest equipment, and so can readily be undertaken by 

 amateurs. In No. 166 of the Harvard College Observa- 

 tory Circulars Prof. Pickering prints a list of 372 variables 

 of long period, and asks for cooperation in the observa- 

 tion of them. Many are already being regularly observed, 

 but more help is required, and, if desired, the results 

 would be incorporated in the Harvard publications. 



