February 26, 1920] 



NATURE 



693 



the two regions this identity would be required by 

 symmetry, but as the warping of space-time is quite 

 different near the sun from what it is at the distance 

 of the earth, does it follow that these two systems are 

 necessarily equivalent? It does not seem to the 

 writer that the failure to find this shift invalidates 

 the Dart of ICinstein's theory from which his law of 

 gravitation is deduced, and it certainly does not Con- 

 tradict this law itself. 



Leigh Page. 

 .Sloane I>aboratory, Yale University, New 

 Haven, Connecticut, January 22. 



1 



Biological Science In Secondary Schools. 



I SHOULD like to direct attention to a very important 

 paragraph in the Report of the Investigators of the 

 Secondary School Examinations Council which is not 

 referred to in the article which appeared in N.mure 

 of February 19 (p. 669). It is the paragraph which 

 deals with natural history and zoology. 



It is quite clear from this paragraph that the 

 Investigators wish to discourage the teaching of the 

 animal side of biology in secondary schools — a very 

 serious matter in itself. But when the Investigators 

 proceed to state that "the principles of biological 

 science can be (better] illustrated by means of 

 botany," they are expounding a doctrine as to the 

 teaching of a science which is bound to have most 

 serious and harmful results. 



The principles of biological science can be taught 

 or illustrated only by persons with a coinpetent 

 knowledge of both botany and zoology, and a sug- 

 gestion such as this, issued as the considered judg- 

 ment of a bodv of educationists, that a knowledge of 

 botany alone is sufficient for this purpose, will only 

 exaggerate the present-day incomix^tence of the 

 teaching of biology in many of our secondary schools, 

 in which the teachers have had no training in zoologx . 

 This matter has already been considered by a repre- 

 sentative meeting of zoologists in London, and steps 

 are being taken to represent the views of zoologists 

 to the President of the Board of Education at an early 

 date. 



Sydney J. Hickson. 



The Victoria I'nivorsity of Manchester, 

 February 23. 



Change of Colour in Captive Birds. 



Mr. H.aroi.d Mii.i..\k invites notes on this subject 

 (Nah;kk, February 5, p. 600). The case of the cross- 

 bill (Loxia curvirostra. Linn.) seems in point. My 

 attention was directed to it some years ago, when 

 I saw a number of crossbills — six or eight, if I 

 rememl)er arieht — confined in a large cage or small 

 aviarv at Glenferness, Nairnshire. The brilliant 

 scarlet plumage which distinguishes the adult male 

 in a state of freedom had changed on these captives 

 to vellowish-olive. and I was informed that this was 

 the invariable effect of captivitv. The late Lord 

 Lilford kept a number of crossbills in his famous 

 aviarv, and has the following note in his coloured 

 "Fit'ures of Birds of the British Isles": — 



"On the vexed question of the plumage of the 

 crossbill, I can only say that every red bird that I 

 ever possessed lost that brilliant colour at the first 

 moult, and never regained it " (vol. iv., p. 76). 



In all the stuffed specimens that I remember to 

 have seen the scarlet hue had faded to the same 

 dingy olive. 



Herbert Maxwki.i.. 



Monreith. 



NO. 262.6, VOL. 104] 



Volcanic Rocks in Northern Kordofan, Sudan. 



In view of the discovery of the Bayuda volcanic 

 field observed by Dr. Chalmers Mitchell during the 

 Times African flight, and referred to by Prof. J. VV. 

 Gregory in Nature of February 19, some interest 

 attaches to a specimen of a volcanic rock sent to 

 the Mineral Department of the British Museum for 

 identification in July, 1912, by Dr. C. G. Seligmann. 

 The specimen was collected by Dr. Seligmann at the 

 base of Jebol Katul, Northern Kordofan, where he 

 found many stone implements made of the same rock. 



Jebel Katul is 350 miles south-west of the volcanic 

 field seen by Dr. Chalmers Mitchell, and is on the 

 trend of the north-east to south-west depression in- 

 dicated bv Prof. Gregory as running froin the coast 

 of the Red Sea south of Adal Qaqa, and following the 

 course of the Nile from Abu Hamed to Korti. 



The rock is very fine-grained and slate-blue in 

 colour, weathering to pale green. Examination shows 

 it to be a riebeckitc-rhvolite showing "flow structure," 

 but too fine in grain to enable the nature of the 

 felspar or the relative amount of quartz present to 

 b* determined. The rock is nearly allied to the 

 riebeckite-rhvolites of Gilgil, north of Lake Naivasha, 

 and to the riebeckite-bearing trachytes of Senaf(? and 

 Fakoda, North .\bvssinia, described by Dr. G. T. 

 Prior in 190^, both of which occurrences are on thie 

 line of the Great Rift Valley. 



\V. Campbell Smith. 



Mineral Departinent, British Museum 

 (Natural Historv), Cromwell Road, 

 S.W., Februarv 23. 



Scientific Workers and a National Federation. 



Considerable misapprehension seems to have arisen 

 with regard to the action taken by the National Union 

 of .Scientific Workers in connection with the inaugural 

 Conference of Professional Associations on February 7, 

 convened for the purpose of forming a National 

 Federation of Professional, Technical, .Administrative, 

 and Supervisor\- Workers. I shall be glad if you 

 will give publicitv to the following statement of 

 fact : 



This union was invited to send delegates to the 

 inaugural conference and accepted the invitation, as 

 there were manv other technical and scientific asso- 

 ciations invited with which it was felt this union 

 had almost identical interests. As the result of the 

 preliminarv discussion, it was found that such bodies 

 as this would be out-voted and out-influenced in any 

 such federation bv unions with which it has little in 

 common. W'ith the help of other associations We 

 moved an amendment in an attempt to prevent the 

 new federation from taking a definite bias at ifs 

 inception. This amendment was lost, whereupon we 

 abstained from takinij further part in the pro- 

 ceedings. . 



The report as it appeared in the Press stated that 

 the resolution to form a federation was carried 

 unanimously, the inference being that this union, 

 which was represented at the meeting, had decided to 

 join the federation, and many of our members, seeing 

 this misleading statement, have assumed that this is 

 the case. I trust that this disclaimer will reassure 

 them and other such persons who are interested in 

 the union. 



A. G. Church, 

 , Secretary. 



National Union of Scientific Workers, 

 in Tothill Street, Westminster, 

 .S.W.I, February 19. 



