346 



KNOWLEDGE. 



September, 1910. 



in a vertical position. The lowering of the wings 

 from behind towards the front is mainly intended 

 for lifting the insect, while the rear motion, from the 

 front to the back, provides for its horizontal advance. 

 The duration of each stroke of the \\ings under 

 normal conditions is remarkabh* constant. Like 



any other muscular contraction it, however, aug- 

 ments with fatigue, as well as with anv decrease in 

 temperature. 



The progress of these interesting experiments will 

 doubtless bring out many other points of value for 

 the science of aviation. 



THE MARKINGS O N M A R S . 

 Bv W. 1'. DENNING. F.R.A.S. 



The precise character of the features on Mars has given rise to 

 ample discussion in recent years. Ever since the late eminent 

 Italian astronomer, Schiaparelli, distinguished markings in 

 1877, which he termed "canals" or "channels," observers 

 have been at variance on the matter, and angry controversies 

 have not resulted in satisfactory issues. 



Some telescopic students of this planet could see no 

 canals at all, others could discern a few of them, while 

 others again detected a great number, and delineated the 

 surface with a geometrical network of lines. 



The canals were also said to exist in pairs, that is, they 

 consisted of double lines like a railway. This singular 

 configuration was supported by several obser\-ers, and as 

 ardently objected to by others. For more than a generation 

 there has been a wide diversity of opinion and a war of words 

 on the subject. 



The question seemed to hardly admit of practical settlement, 

 but the last few oppositions of Mars, and especially that 

 which occurred in the summer of 1909, liave furnislied 

 important evidence calculated to pro\e what the surface 

 markings of Mars are really like. 



The double canals may be said to have been eliminated 

 some j'ears ago, as an optical illusion. And now the network 

 of narrow lines drawn by Lowell, Brenner and others, must 

 similai'ly disappear, as incorrectly representing the visible 

 condition of the planet. That there are dusky canal or 

 channel-shaped markings on Mars must be admitted. Dawes 

 and other observers noticed and figured them many years ago, 

 but they do not exist in the same character or abundance as 

 certain modern observers have affirmed. 



M. Eugene Antoniadi, whose observational and artistic 

 abilities are of a very high order, has laboured most meritor- 

 iously in recent years to ascertain the truth concerning the 

 lineaments of Mars and to picture and describe the surface of 

 the planet just as it appears in nature. With the great 

 327-inch refractor at the Meudon Observatory, Paris, he made 

 a series of observations of Mars in 1909, and his results 

 conclusively disprove the " systems of hard geometricall>-- 

 patterned line; with which some observers have so elaborately 

 endowed the planet." The minor details or " canals " appeared 

 irregular, knotted and disconnected, and presented a perfectly 

 natural appearance. 



Instead of being artificial constructions, such as certain 

 imaginative people would have us believe, we may depend 

 upon it that the markings are the outcome of natural phe- 

 nomena, and that the chimerical theories advanced to explain 

 them deserve no credence whatever. 



M. Antoniadi concluded from the experience he gained with 

 the large Meudon refractor that the performance of a really 

 good large telescope must in\ariably beat that of a smaller one. 

 When the atmosphere was calm and definition good he found 



that the big instrument really possessed a great superiority 

 over those of small size. 



With the recent de\elopments in regard to our knowledge of 

 Mars, I think that all unprejudiced observers will cordially 

 agree. I have viewed Mars under a similar aspect to that 

 described by M. Antoniadi, but of course my smaller instru- 

 ments (ten and twelve-and-a-half inch reflectors) afforded 

 me a less impressive grasp of detail. Twenty years ago I 

 ventured to summarise the results of observations at Bristol as 

 follows : " The detail is visible in the form of irregular streaks, 

 condensations and veins of shading very faint and delicate in 

 some parts. The \eins apparently connect many of the larger 

 spots, and here and there show condensations which have some- 

 times been drawn as isolated spots. A night of good definition, 

 however, reveals the ligaments of shade connecting them." 

 {Telescopic Work for Starlight Evenings, p. 160.) 



Mars is one of our nearest planetary neighbours and 

 certainly one of the most interesting, and the recent work of 

 .•Xntoniadi, Molesworth, Phillips and others, in providing us with 

 thorough and reliable charts of the planet's topography, 

 deserves high commendation. The markings of Mars have a 

 special significance as being parts of the planet's actual surface, 

 ■while the features seen on Jupiter and Saturn are merely 

 atmospheric phenomena. For this reason, apart from their 

 interesting, abundant and varied character, the Martian spots 

 and streaks merit careful study as durable formations on the 

 globe of perhaps the most interesting planet of our system. 



In reporting my observations of Mars in 1903 to the Ast. 

 Nach, 5926, I remarked that "a large number of irregular 

 dusky streaks, different in tone and direction, were observed. 

 Some of these were very distinct, as, for example, Nilosyrtis, 

 Protonilus, Indus, Ganges, Cerberus, Casius, and so on, 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." 



In fact, the streaks or canals were nothing hke the hard 

 dark lines depicted by certain observers. They were rather 

 streams of shading, far from straight or equable in tone, and 

 decidedly ga\e the impression of being natural formations. 



Some of them were as distinct as the fainter belts of Jupiter, 

 and I think that the terms, streak and canal, are quite appli- 

 cable to the appearances alluded to, though many of them may 

 consist of irregular details blended into bands of shading. 

 Some of the belts of Jupiter are made up of a mass of features, 

 and are very far from being smooth belts of dusky material. 

 Under sufficient amplification they would be seen broken up 

 into a great variety of " spots," strung out in a longitudinal 

 direction. This particularly refers to the great South equa- 

 torial belt of Jupiter, which frequently exhibits a procession of 

 condensations, bright spots, wisps and other irregular details. 



