378 



NA TURE 



[Jamuary 28, 1909 



The guide also provides a list of the principal colonial and 

 foreign journals and a variety of general information. 

 This useful work of reference is published at 125 Strand, 

 London, and its price is u. 



The current number of the London Quarterly Rcvicia, 

 which is published by Mr. Robert Culley, is rich in 

 thoughtful articles on subjects receiving great attention 

 just now from intellectual readers. We note, in particular, 

 articles by Mr. J. Butler Burke on materialism and life, 

 and by Mr. Henry GuUiford, of South India, on " Todas 

 and Tibetans: a Study in the Evolution of Religion." In 

 addition to articles, the magazine provides notes and dis- 

 cussions on literary and theological topics, and an unusually 

 large number of reviews of recent books. 



Two large coloured maps, showing respectively the 

 political boundaries and economic products of Brazil, have 

 been issued by the director of the Mission Br&ilienne, 

 28 Boulevard dcs Italiens, Paris. Upon the back of each 

 sheet is printed a large amount of useful information re- 

 lating to the general political and economic geography of 

 the country. 



The Carnegie Institution of Washington has published 

 the seventh of a series of volumes which will form eventu- 

 ally a complete index of economic material in documents 

 of the States of the United States. The present volume 

 deals with California from 1849-1904, and has been pre- 

 pared for the department of economics and sociology of 

 the Carnegie Institution by Adelaide R. Hasse, of the 

 librarian department of public documents. New York 

 Public Library. The scope and character of this exhaustive 

 index have been explained in these columns in referring 

 to previous volumes. 



Messrs. C.^ssell and Co., Ltd., have published a book- 

 let, written by Mr. H. H. Thomas, on " Sweet Peas and 

 how to Grow Them." The text contains just that prac- 

 tical information the amateur gardener requires, and in- 

 cludes numerous illustrations from photographs and 

 sketches. 



OUR ASTRONOMICAL COLUMN. 

 ^ Recent Brilliant Fireballs. — Mr. W. F. Denning 

 writes : — A brilliant Quadrantid passed horizontally, with a 

 slow motion and long course, along the W. heavens on 

 January 6, 8h. 40m. Other fine meteors were noticed on 

 January 7, qh 27m.; on January 11, 5h. 30m., 7h. 40m., 

 8h. iim. ; January 13, gh. 48m.; January 17, 8h. 20m.; 

 January ig, sh. 50m., 7h. som., &c. But the most striking 

 object of all was that of January 11, 8h. iim., and a large 

 number of descriptions of the appearance and position of 

 this brilliant visitor have come to hand. From these I 

 have worked out the real path as follows : — Height, 58 to 

 29 miles over Llandovery to Usk, South Wales ; length of 

 path, 52 miles ; velocity per second, 13 miles ; radiant 

 point, 332°-t-36° ; earth point, Chippenham, Wilts. The 

 meteor was estimated by Mr. H. Chapman, of Newtown, 

 N. Wales, as brighter than the full moon, and it gave two 

 flashes of sufficient intensity to light up the firmament and 

 terrestrial objects for several seconds. The meteor moved 

 slowly from a radiant in the western sky. Several of the 

 observers describe the motion as undulatory, as though the 

 object experienced some difficulty in penetrating our 

 dense atmosphere. The radiant point is not conformable 

 with that of any known meteoric shower, but it falls in 

 the same place as that of an active stream or streams visible 

 in the months of July, August, and September. 



Martian Features. — In No. 34 of the Lowell Observa- 

 tory Bulletins Prof. Lowell describes, and gives the posi- 

 tions of, certain white spots which have been observed in 

 the arctic and subarctic zones of Mars, time after time, by 

 the Flagstaff observers. Eight of these spots have been 

 recorded, and they do not appear to be restricted to any 



NO. 2048, VOL. 79] 



zone, although, individually, they always appear year 

 after year in the same place. The chief of them appears 

 in long. 206°, iaf. 83° N., and was first observed by 

 Schiaparelli in 1SS4 ; in 1903, at Flagstaff, this spot was 

 kept under observation from June 21 to August 10 (Martian 

 dates), being seen at every one of the six presentations. 



To account for the appearance of these white spots a 

 natural supposition would be that they are snow-fields or 

 glaciers on high mountain tops ; but observations show 

 that there arc no considerable mountains on Mars, there- 

 fore the question as to the nature of these phenomena 

 remains to be solved by future discussion. 



In a paper communicated to the Royal Astronomical 

 Society (Monthly Notices, vol. Ixix., No. 2, December, 

 1908) M. .'\ntoniadi discusses a composite drawing which 

 he made from a print showing forty images of Mars, taken 

 at the Lowell Observatory. The analysis of the photo- 

 graphs and the comparison of the results with those 

 previously obtained from visual observations lead to some 

 important conclusions respecting the objective existence of 

 certain features about which various visual observers have 

 hitherto disagreed. In general, the photographs confirm 

 the existence of many features reported by Schiaparelli. 

 Lowell, and others, and, what is perhaps more important 

 in the discussion of the results obtained by different 

 observers at different epochs, they afford strong evidence 

 of change in several important features of the planet's 

 disc, e.g. the Syrtis Major is shown to be of a slightly 

 different shape on these photographs, taken 1907, July 11, 

 from that observed visually by Schiaparelli between 1877 

 and 1888. 



Atmospheric Polarisation. — In an extract from the 

 .\stronomischc Nachrichten (No. 4283) Herr Chr. Jensen 

 discusses the question of atmospheric polarisation, and 

 shows that there are two neutral points where there is no 

 polarisation. These two points are shown to vary with the 

 solar activity and the amount of volcanic dust and other 

 impurities in the atmosphere, and the author suggests that 

 more observations should be made by meteorologists and 

 astronomers in order to elucidate the question of relation- 

 ships suggested by the results of his 'discussion. 



Making a Forty-centimetre (15-7 Inches) Cassegrain 

 Reflector. — In a brief note which appears in No. 4295 

 of the Astronomische Nachrichten M. Schaer describes the 

 method of making a 40-cm. Cassegrain reflector, which 

 he has made and has found very efficient at the Geneva 

 Observatory. 



The large disc is 7 cm. in thickness, and is pierced by a 

 central hole 8 cm. in diameter ; the method of mounting 

 is the older one employed by Herschel, and is found to give 

 sufficient resistance to the flexure of the mirror. 



A great disadvantage in a Cassegrain telescope, as com- 

 pared with a refractor, is the amount of stray light which 

 enters the ocular and reduces the contrast of the image. 

 This may be eliminated by suitable diaphragms, but it is 

 a difficult matter to fix the latter in exactly the correct 

 position. M. Schaer has surmounted this difficulty by 

 mounting a conical tube inside the telescope, so that the 

 stray light is intercepted before it reaches the eye-piece. 

 This conical tube is made of thin sheet iron, and is 

 150 mm. long; the diameter of the open end is 60 mm., 

 that of the eye end 75 mm., and as the focal plane is 

 limited to 70 mm. diameter, this additional tube in no 

 wav interferes with the image. 



Tests made with this instrument indicate that in intensity 

 of the focal image it is superior to a crown-flint refractor 

 of equal aperture, whilst its superiority for photography 

 is obvious in many directions. 



The Poles of Double-star Orbits. — In No. 4291 of the 

 Astronomische Nachrichten Prof. Doberck discusses the 

 relation of the poles of double-star orbits to the ecliptic 

 and to the galaxy. The results show that the poles do 

 not lie along the galaxy nor near the pole of the ecliptic, 

 but it appears to be more probable that they lie along the 

 ecliptic than that they lie near the galactic pole. 



Remarkably Dark Penumbral Eclipse of the Moon. — 

 Visual observations and photographs m,ide at the Juvisy 

 Observatory show that the penumbral eclipse of the moon, 

 which took place on December 7, 1908, was an exception- 

 ally dark one. By giving short exposures on slow plates 



I 



