334 



NATURE 



[November 27, 1919 



other Dutch port, even including Rotterdam ; and the 

 "extraordinary idea" of putting a toll on boat and 

 cargo for the upkeep and improvement of the water- 

 way is as old as the Roman Empire, and was the 

 actual rigime on the Rhine in the most prosperous 

 days of its commerce — under the French. 



I entirely agree with what Dr. Geyl says about 

 the canal dimensions and their origin, but it does not 

 touch my really serious and deliberate assertion that 

 Belgium has suffered, and is suffering, from gross 

 " international servitude." L. VV. Lyde. 



University College, London. 



The Colours of Racehorses. 



In my " Origin and Influence of the Thoroughbred 

 Horse" (1905, pp. 441 ^.) I supported my other argu- 

 ments to prove that the " blood " horse originated in 

 Libya (North-West Africa), and that his primal colour 

 was bay, by giving in one table the results of my 

 examination of the colours of the winners of the 

 Derby, the Oaks, and the St. Leger, and in another 

 table the colours of the first three horses in each of 

 these races in the three decades from 1870-99. Grey 

 does not appear in them at all, and black onlv twice, 

 whilst chestnut — which (like brov/n, black, and grey) 

 I maintain is not an original colour, but due to cross- 

 ing the bay Libyan horses and the ancient dun horses 

 of the Upper European-.Asiatic area — shows a steady 

 decrease. 



In view of the discussion aroused bv the winning of 

 the Derby by a grey (Tagalie) in 1912, and by a black 

 (Grand Parade) in the present vear, it may interest 

 some of your readers if I give my tables brought up 

 to date for the last fifty years : — 



Table I. — 'Winners. 



It will be seen that in the first three decades chest- 

 nut gave way steadily to bay and brown ; that in the 

 fourth decade chestnut dropped i in the winners, but 

 regained a little in the lower horses (19 against 16); 

 that in the present decade, whilst it retains the same 

 number of winners as in the last, iL has lost the 

 slight gain made in the lower horses; and that in the 

 fourth decade ba\ dropped in the winners from 17 to 

 15, and in the total from 54 to 47, but the loss in the 

 winners is more apparent than real, since four bav- 

 or-browns were amongst the winners. In the present 

 decade, in spite of the reappearance of black and grey 

 amongst the winners, bay has more winners (18) than 

 ever before, though in the total number of hoi-ses it 

 has not quite regained its old position (c;4). 



Thus, in defiance of the sporadic reappearance of black 

 and grey, bay seems steadily bent on superseding all 

 other colours. Wili.i.^m Ridgeway. 



Flendyshe, Fen Ditton, Cambridge, 

 November 4. 



NO. 2613, VOL. 104] 



Gravitation and Light. 



It ma\' or may not have been noticed that the 

 refractivity (/*— i) at any point, required to produce 

 the Einstein deflection, is the squared ratio of the 

 velocity of free fall from infinity to the velocity of 

 light. Oliver Lodge. 



Mariemont, Edgbaston, November 24. 



Variation of Refractive Indices. 



' Mr. Twyman (N.ature, November 20, p. 315) will 

 find in Trans. Chemical Society (1906, vol. Ixxxix., 

 p. 417) an account of some observations by Miss Florence 

 Isaac and myself which indicate that the refractive 

 index of a solution of sodium nitrate at the surface 

 of contact with glass is slightly greater than that of 

 the same solution in contact with calcite. 



It was our intention to continue and extend these 

 observations, but we have never been able to do so. 



Henry A. Miers. 

 The L'niversity, Manchester, November 22. 



Neon. 



L\ response to inquiries, may I use vour columns 

 to make two announcements in reference to the 

 above ? 



First, by making use of a new and more powerful 

 method of positive-ray analysis (the description of 

 which is now in the press), I have succeeded in 

 obtaining measurements of mass and other evidence 

 of sufficient accuracy to prove beyond all dispute that 

 atmospheric neon (atomic weight 20-200, 0= 16) is a 

 mixture of two isotopes of atomic weights 20-00 and 

 2200 correct to about i/ioth per cent. 



Secondly, permission to publish being now granted, 

 a full account of recent experiments on " Neon Lamps 

 for Stroboscopic Work " will shortly appear in the 

 Proceedings of the Cambridge Philosophical Society. 



F W. .\STON. 



Cavendish Laboratory, Cambridge, ■^mi 



November 19. iHl 



Bird Migration. 



The captain of the Portuguese steamer Bolama^ 

 recently touching here on her voyage from Cape 

 Verde Islands to Lisbon, reports that near the Canary 

 Island, Las Palmas,, his ship was visited bv 

 an immense cloud of swallows settling in 

 thousands upon every part of the vessel and resting 

 until early dawn, when almost every bird departed. 

 Nothing is known as to the direction in which the 

 birds were travelling or why they should be found far 

 away over the open sea in such a southerly latitude. 

 Two swifts are perennially present and nest at 

 Madeira, but the chimney-swallow is only known as 

 a rare straggler; and in the last fifty-five years I 

 have not known of the passing of anv migrating- flock, 

 though our latitude is five hundred miles north of the 

 locality indicated in the Bolama occurrence. So 

 strange an incident might be taken from the pages of 

 Pliny or .Ambroise Pare, and cannot fail to interest 

 those of your readers who are working on the subject 

 of migration. Michael C. Grabham. 



Madeira, October 27. 



Luminous Worms. 



From the communications which reach me I learn 

 that this subject is creating a great deal of interest. 

 .'\t the same time all the information is vague and 

 unsatisfactory, and I am unable to obtain specimens 

 of the creatures themselves. The vagueness of the 

 information is due in great measure to the lack of 

 knowledge which still prevails respecting the Oligo- 



