40 



NATURE 



[November lo, 1910 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible iot opinions 

 expressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications.] 



Origin of Dun Horses. 



In discussing the colours and stripes of horses in 

 *' Animals and Plants under Domestication," Mr. Darwin 

 says : — " I have endeavoured, but with poor success, to 

 discover whether duns, which are so much more oftener 

 striped than other coloured horses, are ever produced from 

 the crossing of two horses, neither of which are duns. . . . 

 One case, however, has fallen under my own observation 

 of a foal from a black mare by a bay horse, which when 

 fully grown was a dark yellow-dun and had a narrow but 

 a plain spinal stripe."' 



In a recent number (October 15) of the Veterinary 

 Record Mr. J. B. Robertson gives the following instances 

 of reversion to dun from the last eleven and first four 

 volumes of the General Stud Book : — 



(1) Bay-dun filly (1907), by Ash (chestnut), out of 

 Unexpected (bay). 



(2) Dun filly, Sarah Curran (1892), b\' Robert Emmett 

 (bay or brown), out of Cellulites (black). 



(3) Dun colt (1897), by Sir Frederick (bay), out of 

 Lobelia (bav or brown). 



(4) Light' dun filly (1886), by Lord Gough (bay), out of 

 Danseuse (brown). 



(5) Dun or chestnut filly, Sancta (1884), by Exminster 

 (bay), out of Halloween (chestnut). 



(6) Dun filly (1763), bv Young Cade (bav), out of Miss 

 Thigh (grey). 



(7) Dun colt (1730), by King George II. 's one-eyed grey 

 Arabian, out of Young Kilty Burdett (bay). 



(8) Dun fillv (1829), bv Lotterv (brown), out of Octavia 

 (bay). 



Mr. Robertson also mentions (i) that a half-bred yellow- 

 dun filly was obtained out of a liver-chestnut ^^'elsh cob by 

 a bay thoroughbred with a dorsal band — this fill}' " during 

 early foalhood was profusely striped on the face, neck, and 

 quarters"; and (2) that of 45 duns given in the tables 

 included in his paper, 39 cannot be traced to an original 

 dun ancestor. They sprang from the union of Silver- 

 locks (chestnut) and the Godolphin Arabian (brown), " and 

 hence afford incontrovertible evidence that a gametic line 

 of duns — which in this case extended to four generations — 

 may spring from parents neither of which are dun." 



The L'niversity, Edinburgh. J. C. Ewart. 



Markings of Mars. 



I HAVE recently returned by way of Tasmania from a 

 series of visits to the chief observatories in the United 

 States, which included a month's stay at the Lowell 

 Observatory during the past opposition of Mars. This 

 visit was made with the express object of testing by my 

 own observation the reality of the data on which Dr. 

 Lowell has based his speculations. 



I find on my return that so much scepticism has been 

 raised by the observations and arguments of M. Antoniadi 

 and others that a record of my own experience may be 

 of some vahie. 



When I first looked at Mars at FlagstafT (September 27, 

 1909) I saw with great difficulty three streaks, presumably 

 canals. The seeing was bad, and the general faintness 

 of the planet's markings at that time is admitted by all. 

 I continued to observe Mars on every possible night (which 

 was nearly every night) until October 25, and as my eye 

 became accustomed to the work I saw more and more. 

 The canals were seen repeatedly better — this with the 

 24-inch refractor generally stopped down to about 

 18 inches. I found that with more than 20 inches the air 

 was nearly always too unsteady, and with less than 

 15 inches too much separating power was lost. The 

 canals were seen best with a power of 390 diameters. 



Clearer they became each night until, on October 25, 



■I " Animals and Plants under Domestication," vol. i., p. 62. (1872.) 



NO. 2 141, VOL. 85] 



the seeing being the best I ever experienced, the canals 

 came out with amazing clearness and steadiness, sharp and 

 clean, like telegraph wires against the sky, the oases als(^ 

 being exquisitely defined. Whereas on previous nights th- 

 canals could be held only by short glimpses of perhap> 

 half a second at a time, they were now steadily visibl- 

 for three or four seconds together, when a short flicker 

 would sweep over them ; during the lucid intervals th- 

 limb also of the planet was perfectly steady, as I hav 

 never seen it before or since. Of the objective existenc 

 of these markings in the image at the focus of the tele- 

 scope there could be no manner of doubt, and Lowell ''^ 

 representations of them are nearer the actual appearanc 

 than any I have seen, though even in his drawings th' 

 lines seem hardly fine enough. The effect produced on my 

 mind by this remarkable definition, which lasted for 

 upwards of one and a half hours (from about 8.30 until 

 after 10 p.m.), was staggering and ineffaceable. Soon 

 after ten the definition went to pieces. 



It may be relevant to mention that a few evening-^ 

 previously I had obtained a fair and convincing view of 

 the canals with the 40-inch reflector (full aperture and a 

 power of about 700), when they had appeared hazy and 

 broader, but the image had been very unsteady, and only 

 obtained in very short flashes ; but nothing that I had 

 hitherto seen had prepared me for the astonishing steadi- 

 ness and fineness of the details visible on this superb 

 night. 



There is in my mind no sort of doubt that the revela- 

 tion of this night was due both to the perfection of the 

 instrument (which its maker long ago pronounced to be 

 the best that the firm of Alvan Clark ever turned out) and 

 the atmospheric conditions which are found at Flagslaff. 

 With respect to these I would mention, as pointing to 

 the freedom from water vapour, that I have seen the 

 thermometer fall from more than 70° F. at 3 p.m. to 

 below the freezing point at 3 a.m. without a ti'pce of hoar- 

 frost, and the general clearness of the air was such that 

 I could see Uranus with the naked eye within 5° of the 

 horizon, and could nearly every night count nine star?; 

 in the Pleiades and separate e and 5 Lyrse. 



The telescope also afforded on other nights ampli 

 evidence of the extraordinary clearness of the air. On 

 many occasions both satellites of Mars, when not ver\ 

 near the limb, could be seen, without screening the planet, 

 with 18 inches of aperture ; and on one occasion with this 

 aperture I picked up one of them unawares while looking 

 for canals with a yellow screen. (N.B. — The importance 

 of colour screens in rendering the canals visible does not 

 seem to be sufficiently appreciated.) 



In the face of .ill this positive evidence, and in the 

 absence of any evidence that the observing conditions at 

 Mfudon, just outside Paris, ever approach these best con- 

 ditions at Flagstaff, I find it impossible myself to attach 

 any serious weight to the ingenious and plausible conten- 

 tions of M. Antoniadi. which seem to have been much too 

 hastily accepted in this country. 



.As to the deductions which Dr. Lowell has drawn from 

 his observations I have nothing to. say except that the 

 startlingly artificial and geometrical appearance of thf 

 markings did force itself upon me. 



James H. Wortmincton. 



Wycombe Court, High Wycombe, October 31. 



November Meteors. 



The moon is full about the time when the Leonids 

 become due in the present year, but that is no reason why 

 these meteors should elude observation, for the Sickle h.a-; 

 furnished some notable displays of shooting stars. With 

 the moon in opposition in mid-November, as, for instance, 

 in 1799 and 1867, though the coming apparition cannot 

 be expected to vie as regards brilliancy with either of 

 these historic events, yet in its way it may not prove un- 

 important nor be allowed to pass unobserved. Besides the 

 Leonid epoch, there are also some other meteoric events 

 that occur in November, of which the following par- 

 ticulars have been computed by the writer : — 



Epoch, November 11, 9h. (G.M.T.), approximately 

 second order of magnitude. Principal maximum. 



