Mar., 1904.] 



KNOWLEDGE & SCIEXTIEIC NEWS. 



41 



ASTRONOMICAL. 



Mr. Denning's Observa.tions of Mars 

 in 1903. 



In the Astroiu'iiiisilw S'liiliiichten, No. 3426, Mr. F. W. Demiiiig 

 gives the main results of his observation of Mars with a lo-inch 

 reflector, in the Spring of 1903. The powers that he used 

 ranged from 252 to 4S8. but the one most commonly employed 

 was 312. He noted that occasionally there were decided 

 changes in the visible appearance of certain markings, and 

 these changes were obviously not due, either to uncertain 

 seeing, or to the varying inclination of Mars, but, in the 

 observer's opinion, to local vagaries in the Martian atmosphere. 

 Thus, on May 6 and 7, he saw a white band dividing the canal 

 Nilus, not seen on March 31 or April 2, and not shown on the 

 charts, .\gain, on May 21. the northern region of the Syrtis 

 Major was very dark, with a white cloud on its southern edge, 

 but on May 23 and 24 the whole Syrtis Major was very faint, 

 as if veiled by the cloud spreading northwards. As regards 

 the " canals," Mr. Denning says : " ,\ large number of 

 irregular dusky streaks ^canals), different in tone and direction, 

 were observed. Some of these were very distinct, as, for 

 example, Nilosyrtis, Protonilus, Indus, Ganges. Cerberus, 

 Casius, &c., while others, as Phison, Euphrates, Gehon, were 

 feeble or extremely faint and delicate. Many of them were 

 knotted or strongly condensed in places, and particularly so at 

 those points where either a junction or intersection of two of 

 them occurred." Mr. Denning considers these streaks as 

 certainly objective. He says that they were single, though in 

 a few instances two of them w-ere placed tolerably near to- 

 gether, running in appro.ximately parallel directions. He is 

 emphatic that the " prolific system of double canals delineated 

 by some observers had no existence " during the period of 

 observation, as far as his eye and telescope could determine. 

 Comparing these recent observations with those made in 

 February, i.S6g, Mr. Denning deduces from I2,ij6 rotations of 

 Mars, the value 24 h. 37 m. 22-7 s. for the rotation period. 



The Double Carvals of Ma.rs. 



Mr. Lowell, in Bulletin No. 5 of bis Observatory, gives 

 evidence against the hypothesis that the gemination of the 

 Martian canals is an interference effect. If it were so, the 

 width between the two components of a double canal should 

 vary inversely as the aperture. To test this, Mr, Lowell ob- 

 served a number of double canals with the full aperture of his 

 telescope ^24 inches), and then with that aperture reduced to 

 18, 12, and 6 inches. His measures of the drawings made 

 under these several conditions showed that the apparent 

 angular separation did not increase as the aperture was 

 diminished ; that the separation was invariable within the 

 limits of observation for any particular canal, but differed for 

 different canals, bearing no relation to the width of an inter- 

 ference pair of lines. 



Mr. Lowell's ObservaLtions of Ven\js 

 in 1903. 



In Bulletin No. 6, Mr. Lowell classes the markings to 

 be made out upon Venus under two heads. The first includes 

 the collar round the south pole and the two spots on it, and 

 the nicks inward from the terminator. Of these Mr. Lowell 

 states he has ahvaysbeen certain, and "they alone are sufficient 

 to show that the planet's rotation is an affair of about 225 

 days." The second class include the long shadings from the 

 centre of the disc to the terminator, and of these, also, Mr. 

 Lowell asserts " the objectiveness beyond the possibility of 

 illusion." It will be seen that in this assertion Mr. Lowell is 

 withdrawing his withdrawal of these markings which he pub- 



lished some eighteen months ago in tlir Aslivnoniisclti' 

 Xiichrichltii. No. 3.S23. Mr. Liiwell furtluT adds that these 

 streaks "bear no resemblance whatever to the ' canals '. of 

 Mars, They are faint streaks or spots. . . . Tlu-v .ire not 

 of even width, are not dark, and shai^iicul,^ .^ , . I'urllier- 



more, they are of a much higher order ortlill^iMtv c;l'vul(i»jj,s 

 the conditions of visibilitv arc such as to sliilWajo ohsersi-r iTuT 



'canals' of Mars with ease, 



^i.^o saowajo^kse . 

 aiuty, it wcreliSfTess to 



attempt this much harder plaiic*'.* Vjl-!ijt'il6^i^|}37s,WW' Lowuli 

 Bulletin ch- la Socictc'^:\str,mnn,,,,ur^}»l l-i>mflU: 



etle^ 



ly 



wrote in the 



" Lcs configurations out tonjours dJiHrt ■^ 

 en veritc que celles de la Lune. ' In 

 for December, 1S96, lie wrote ; " The markiii,L;r. .nr iHuiniisi 

 and well defined ; their contours standing out sharply against 

 the lighter parts of the disc. . . . The seeing must l)e dis- 

 tinctly bad to have the more prominent among them not discer- 

 nible." This would seem to show that the definition at Flagstaff. 

 Arizona, has changed seriously for tiie worse in the last seven 

 years, whilst a comparison of the drawings of Venus, given in 

 ttie Bulletin, with those of M.ars, such as in I'opitli::- 

 .Istroitiiiny for y\pril. iiS()5, would not lead to the conclusion 

 that there was any essential difference lietwcen tlie streaks on 

 the two planets. 



Calcium and Hydrogen Floccxili. 



A memoir of quite exceptional interest is given on the 

 subject by Professor G. F. Hale and Mr. Ellerman in Volum. 

 III., Part I., of the Puhlutilioiis vf the Yirkcs Observatory 

 Its subject is the minuter study of the surface of the sun by 

 means of the spectroheliograph. The first point brought out 

 is the essentially granular structure of the calcium fiocculi, 

 the entire surface of the sun showing a fine mottling when 

 photographed on the l)right K-hne, The next point is the 

 study of these calcium clouds at difi'i-rent levels, the result of 

 the examination bringing out in a striking manner the way in 

 which the calcium bright clouds expand as they rise higher. 

 The detection of the dark hydrogen fiocculi is another feature, 

 and the fact that they often correspond, though not precisely, 

 with the bright calcium fiocculi. Last of all the discovery of 

 dark calcium fiocculi was established, and the necessity for 

 further work with spectroheliographs of much higher disper- 

 sion, and working upon larger images of the sun, is insisted 

 upon. The memoir is illustrated by fifteen extremely fine 

 photographic plates. 



The Nebulae. 



The Siiictccnth Century (iiui After for I'ebruar}' contains 

 an article on " The Nel)ul;c," l>y the Rc\'. ICdnumd Ledger 

 (iresham Lecturer on Astronomy, whicli summarises with 

 admirafjle clearness and precision, the state of our present 

 knowledge respecting these mysterious objects, and the con- 

 nection with them of the stars. 



ZOOLOGICAL. 



At the meeting of the Geological .Society lield on January 20 

 Dr. A. Smith Woodward, of the British Museum, definitely 

 determined th(^ .systematic position of the cretaceous fishes of 

 the genus I'tycliudus, whose large, quadrangular, ridged crush- 

 ing teeth are such familiar objects to collectors in the chalk- 

 pits of the south-east of England. It has long been known 

 that I'lychudus was an elasmobranch fish, and Dr. Woodward 

 himself had some years ago pointed out the probability of its 

 being a ray, or skate, rather than a shark. The truth of this 

 conclusion is fully demonstrated by a specimen of the jaw 

 cartilages recently discovered near Lewes, which serve to show 

 that these fishes were allied to both the eagle-rays and the 

 sting-rays, and probably, therefore, the ancestral type of bolli. 

 A photograph was shown at the meeting of a splendid .\mcri- 

 can specimen of the dentition of Ptychudus, witfi the teeth in 

 their natural position, forming longitudinal rows. 



* ;;■- 



Fossil Birds- 

 Certain fossil bird reiriains were discussed by Dr. C. W. 

 .Andrews at the meeting of the Zoological Society held on 



