68 



KNOWLEDGE & SCIENTIFIC NEWS. 



[April, 1904. 



dusky knots (called Oases by Lowell, who claims to have 

 discovered them) were distinctly seen here in 1S84, 1886, 

 and other years. In Natuvc for June 3, 1886, I refer to 

 the canals as •' linear shadings with evident gradations in 

 tone and irregularities occasioning breaks and condensa- 

 tions here and there." 



The ingenious experiments conducted by Messrs. 

 Maunder and Evans {Montlily Notiiis, June, 1903) e.xplain 

 some of the observational results without throwing doubt 

 on the whole canal-system of Mars, as some readers have 

 supposed. Certain of the canals are indeed so conspi- 

 cuous as to form objective features comparable in point 

 of distinctness and certainty with the dark belts of [upiter 

 and Saturn. 



If we could greatly enhance telescopic power and 

 examine Mars under a sufficiently amplified disc, the 

 canals would probably look very different to those shown 

 in the miniature views supplied in ordijiary instruments. 

 We should see them as large blotchy bands of dusky 

 material having no resemblance whatever to sharply-cut 

 waterways. The south equatorial belt of Jupiter consists 

 of a series of spots, and it presents a curious transforma- 

 tion under magnifying powers of 50 and 300. With the 

 former it forms a \ery dark narrow streak, but with the 

 latter it is broken up into masses of flocculent material 

 covering an extensive track. 



If the existence of the Martian canals has been doubted, 

 it is partly the fault of certain observers who ha\e greatly 

 multiplied the real number of these objects, drawn them 

 under unnatural aspects, and elaborated the general 

 appearance of Mars in a manner palpably inconsistent 

 with telescopic revelations. 



Mr. Story remarks that " it is time an end should be put 

 to the inquisitorial fashion of refusing credence to scientific 

 discoveries." It is true that certain forms of criticism 

 merely harass and embarrass observers, without effecting 

 any useful purpose. On the other hand, we cannot unre- 

 servedly accept everything offered us in the way of 

 observation, real and \isionary, objective and subjecti\e. 

 Astronomical history would form a curious medley of 

 fact and fiction (chietiy the latter) if all the supposed 

 " disco\eries" of past years were credited and reiterated. 

 Criticism has occasionally proved a wholesome and 

 necessary corrective to results of abnormal and unsup- 

 ported character. 



Conflicting testimony in planetary observation is usually 

 attributed to the differences in telescopes, eyesight, and 

 local atmospheric conditions. But the more potent cause 

 is to be traced to the observers themseKes, who differ 

 widely in their discretion, judgment, and interpretations. 

 One man will accept and possibly elaborate extremely 

 delicate features very imperfectly and uncertainly glim psed. 

 Another will absolutely reject similar appearances. Two 

 things conae actuely into play and are directly opposed, 

 viz.: (i) The dominating deaire to glimpse novelties and 

 gain repute by eclipsing past records ; and (2) the 

 necessity of accepting only what is certainly and steadily 

 seen to the exclusion of all doubtful features. On these 

 points obser\ ers differ vastly ; some of them do not 

 sufficiently realise their responsible positions, and hurriedly 

 make records not justified by telescopic evidence; others 

 are perhaps too punctilious and apt to reject details which 

 are real, though only faintly and fitfully glimpsed. 



In judging the quality of results it should be remem- 

 bered, as a most important factor, that the individual 

 characteristics of the observer play a very prominent 

 part. Some people possess the faculty of seeing objects 

 double. (Jthers will invariably discern novelties where 

 none are visible. Others, again, will detect canals as a 

 necessary feature of a planetary disc. Thus Mercury and 



Venus have been supposed to display these markings very 

 conspicuously. Phenomenal vision will not explain the 

 anomalies alluded to. Objective markings are capable of 

 being corroborated without any difficulty. The spots on 

 Saturn were distinguished by many observers shortly 

 after their discovery. There is no reason why canals 

 should prominently diversify IMercury and \'enus as seen 

 by one observer, while as viewed by others the discs of 

 those planets appear, under the best circumstances, abso- 

 lutely free from such markings. On many occasions during 

 the last few years the beautifully defined disc of Venus 

 has been examined by the writer, but not the v^estige of 

 a canal has ever revealed itself; yet at the Lowell Obser- 

 vatory, Mexico, " the markings are perfectly distinct and 

 unmistakable, invariably visible, and nothing but a very 

 unsteady air can obliterate them " [Montlily Notices, 

 Vol. L\TI. 1896-7, pp. 149 and 402). 



Flammarion was probably quite correct in his expres- 

 sion (" Knowledge," November, 1897) that " the maps 

 of Venus made up to the present time are illusions." 



But our present concern is with l\Iars. The story of 

 his canal-like markings is a true one, though it has been 

 occasionally exaggerated, and it will survive all the oppo- 

 sition levelled against it by sceptics and incapable ob- 

 servers. The northern hemisphere of the planet seems 

 replete with dusky streaks forming the canals. They 

 may not indicate water courses, and their real aspect may 

 be something very dissimilar to that displayed in ordinary 

 telescopes, but with the means employed observers are 

 correct in representing many of them as lines and bands 

 of shading connecting the more bulky spots. 



The Spinthariscope. 



The ingenious mstrument to which Sir William Crookes 

 gave the name of the Spinthariscope, and which he de- 

 vised to show the torrent of rays or the fragments of 

 atoms which are continually being shot out from radium, 

 is now a familiar object to most scientific people. The 

 instrument as is well known consists of a little screen of 

 zinc sulphide or blende, at a slight distance from which 

 a fragment of radium bromide is situated on a pointer. 

 ,\s the emanations from the radium strike the screen 

 they produce an effect similar to that which a bullet pro- 

 duces when it strikes a target, and by means of a magni- 

 fying glass the phenomenon is rendered clearly visible. 

 The instrument is now made by Messrs. A. C. Cossor, 

 and one of them which has been sent to us shows the 

 scintillation with remarkable clearness and \i\idness. 

 It is, perhaps, the most ingenious, and certainly 

 the most lasting, scientific toy that ever has been 

 produced. 



Some time a^o, in a lecture to the Camera Club, Mr. Duncan 

 deitroyed the poetic belief, relating to the nautilus, which is 

 expressed in Popes lines: 



" Learn of the little nautilus to sail, 



Spread tliine oar and catch the driving gale " — 

 bv remarking that the little sails which the nautilus was popularly 

 and poetically supposed to spread were, in fact, never raised at all, 

 but were always tightly clasped about the shell. In a paper con- 

 tributed to the Xatuittl History Miigit::inc. Captain Barrett Hamilton 

 disturbs an idea relating to the wings of the flying fish that is at 

 least ecjually widespread. In the true frying fish Captain Hamilton 

 says the " wings " are never moved as organs of flight. They may 

 vibrate or quiver under the action of air currents, or a shifting a 

 little of their inclination by the fish, but the whole motive power 

 is supplied by the powerful tail. The wings are a parachute to 

 augment the action of this propeller. Their motions are in no way 

 comparable to those of the v.ings of a bird. 



