December 15, 1910] 



NATURE 



207 



In large atolls, on the other hand, the periphery is small 

 relatively to the size of the lagoon ; there is less secretion 

 and formation of coral sand by the living outer surface 

 than is removed in solution from the lagoon, which is, in 

 onsequence, widened, deepened, and reduced to a more 

 '•r les* uniform appearance. 



Madge \V. Drummond. 

 Challenger Office, Villa Medusa, Boswell Road, 

 Edinburgh, December 6. 



Positions of Birds' Ntsts in Hedges. 



About a year ago I wrote to Xatcre (December i5, 

 1Q09) giving certain facts which I had noticed with regard 

 ) the position selected by birds when building. There 

 ^;emed to be good reasons for such selection, but I 

 wanted to know whether the conditions I had noticed were 

 local or general. The letter sent to N.ature by Mr. A. R. 

 Horwood showed that similar conditions were found in 

 Leicestershire, Shropshire, and Surrey. Of the informa- 

 ion which reached me directly, one letter deserves men- 

 ion. 

 Mr. Francis G. Cousins enlisted some of the boys of the 

 Johnstone Schools, Durham, as observers. Out of eight 

 nests, the positions of which are given in the terms of 

 ny letter, two only faced north, one faced north-west, 

 our south-east, and one south. I quote the following 

 ote sent by these observers : — " In the north-east of the 

 listrict, with fairly open country, the nests faced north- 

 ist, and at their rear Tt'os a vast extent of woods. In 

 he south-east of the district the nests face south-east, 

 ■ith woods again at their backs and open country in 

 ':"ont. " The italics are mine. I need not labour the 

 inclusion that birds seek sun and warmth when building 

 heir nests. In this connection it is interesting to quote 

 n observation made by Mr. Roosevelt (" African Game 

 frails." p. 290). He notes that, in Guaso Nyero, just 

 orth of the equator, the weaver birds place the mouth 

 f the nest invariably towards the north, away from the 

 -:rong. prevailing winds. 



J. H. Tlll Walsh. 

 Heath House, St. Faiths, Norwich, December 11. 



Tribo Luminescence of Uranium, 



I HAVE not seen in recent literature any reference to 

 he " tribo " luminescence shown by uranium salts, and 

 V metallic uranium in particular. Having accidentally 

 cnocked over a bottle containing 2 grams of the latter 

 -ubstance, I was surorised to see the bottle glow with 

 : brilliant yellowish-white light, and on shaking the bottle 

 he luminositv could be maintained to such an extent that 

 he label on the bottle was read with ease, and the general 

 'lumination seen easily throughout a large lecture-room. 

 The best way to see the glow is to bring the bottle sharply 

 l>>wn on the nalm of the hand. 



On repeating the exi>eriment with compounds of 

 .ranium, the nitrate and vellow oxide show the same 

 flFect, but to a very much smaller degree, whilst the 

 :'lack oxide and sodium uranate do not give it. 



I expect the above must be known to workers with 

 uranium salts, but it mav be useful to some of your 

 r-^aders to know a method by which tribo luminescence 

 nay be so easily demonstrated. 



W. A. Douglas Rudge. 

 Grey University College, Bloemfontein, November 18. 



MARKED BIRDS IX TWO SENSES^ 

 (i) 'ipHE interesting brochure referred to below gives 

 *■ an account of the bird observatory belonging 

 to the German Ornithological Societ\- at Rossitten, 

 which, already well known, is likely to become in the 

 future of prime importance in securing data, by local 

 observations and by the labelling of living' birds, 



1 (i) " Di» Voge'wa-te "^oss-tten Her Deiusrhen Omithologischen Oesell- 

 scha*"! un'l da< Kennreicbnen der VOgel." By Dr. J. Thienemann. Pp. 36. 

 (Berlin : Paul Parey. lOio.) 



(?) " A-grettc!; and Rtrd SVin« : the Truth about their Col)»'Ction and 

 KTport." Bv Harol-I Ham >1 Smith. With a Fore*-ord bv Sir J. D Ree<: 

 K.C.I.E, C.V.O., MP. Pp. iv-f-138. (fondon: John Bale, Sods, and 

 Danielsson, Ltd., 1910.') Price 55-. 



NO. 2146, VOL. 85] 



towards the determination of many obscure questions 

 in bird migration. 



Rossitten is situated on the narrow belt of sand- 

 dunes, lying between Cranz and Memel, which bank 

 out the Baltic Sea from the Kurische HafF, the more 

 northern of the two lagoons chiefly forming the 

 seaward face of East Prussia. The station — mainly 

 designed by Dr. Thienemann, the distinguished 

 ornithologist — was established in Januan,-, 1901, and 

 fitted up at the expense and under the auspices of the 

 .>iinisters of Education and Agriculture. Being, 

 therefore, a State institution, it will possess greater 

 stability than it could have had under the private enter- 

 prise of the society alone. Dr. Thienemann is director 

 of the station, and holds with this post that of Custos 

 of the zoological collections of the neighbouring uni- 

 versity- in Konigsberg. Ulmenhorst, the actual de- 

 signation of the observatory-, derives its name from 

 the generous lord of the manor, Herr E. Ulmer, who 

 presented, in 1907, the present buildings in a new and 

 more favourable site, some seven kilometres from Ros- 

 sitten, than the original installation. Here Dr. Thiene- 

 mann and his assistants, cut off from the world, spend 

 the drean.' and stormy season of the year from 

 October i to May i. The station stands on the nar- 

 rowest part of the sand-spit, whence the observers 

 have a free and unrestricted view of the aiea between 

 the seaward and the inner sandhills, and can study 

 the birds which specially collect there under genuinely 

 natural conditions. Previous obser\'ations made along 

 this stretch of sand-dunes, on the movements of the 

 hooded crow (Corvus corax), proved that a migration 

 route of great importance passed along it. and that 

 everv vear it was a rendezvous for flocks composed of 

 the same individuals. The site, therefore, though 

 peculiar and isolated, has been deliberately chosen 

 because of its special advantages. 



The chief objects of the obser\'ator\' are to record 

 the exact dates and composition of the migration 

 flights, with the numbers and age of their component 

 species ; the direction in which the birds travel ; the 

 velocity and altitude of their passage (to be determined 

 bv the use of field telephones and box-kl^es), and the 

 atmospheric conditions prevailing during its continu- 

 ance, with the effect of any changes on the migratory 

 stream. Manv other cognate questions are to be 

 inquired into, such as bird-life in relation to food 

 supply, moulting, and colour changes in the plumage 

 at different ages, the economical value of birds, and 

 the most suitable means of protecting useful species. 

 It is intended also to form extensive collections of the 

 skins and internal parts of the birds of the Xehrung 

 and neighbourhood for reference and systematic study. 

 The scope of these observations as proposed to be 

 carried out at Rossitten, if covering a somewhat wider 

 field than, does not greatlv differ from that undertaken 

 bv, the committee of the British Ornithologists' Union 

 and bv other observers elsewhere. Valuable as the 

 obser\-ations all are, however, they do not, as was 

 pointed out in Nature of May 26, 1910. seem likely to 

 carrv us further forward than we at present are to- 

 wards the solution of the phenomena of migration, 

 until such observatories are more numerous and widely 

 distributed ; for what is now required is to trace indi- 

 vidual birds or flocks along every part of their route 

 from their birthplace to their winter quarters, and 

 back again several times. These feathered armies may 

 change their altitude, speed, and direction, or may 

 break up into several battalions beyond the nearest 

 horizon of an isolated observaton.-. and be affected in 

 front and in rear by weather conditions unobservable 

 from it. Even such bird observatories are as yet few in 

 number. There is one at Riga, one in Algiers, another 

 in Heligoland, and the one. so well known, at Buda- 

 Pesth, which cooperates with an observer in almost 



