December 2, 1922] 



NA TURE 



753 



a caricature of natural selection. He appealed for 

 the study of individual life forms. 



Prof. A. C. Seward considered that the great 

 uniformity of the curves presented by Dr. Willis 

 and Mr. TJdny Yule was suspicious, for Nature had 

 not been uniform. He pointed out that, as regards 

 conifers and ferns, study showed that the forms 

 existing now in restricted areas were the oldest and 

 not the youngest. 



Mr. Julian Huxley contended that many factors 

 played a part in evolution. Species characters should 

 be analysed by the methods of genetics and physiology 

 before it could be said which were useless. Apparently 

 useless characters in the Gipsy moth were correlated 

 with physiological differences, such as rate of growth, 

 which harmonised with the environment. 



Prof. R. Ruggles Gates considered that Dr. Willis's 

 view was a corollary of the mutation hypothesis, and 

 emphasised the importance of the extinction of forms 

 as a factor in evolution. 



Prof. W. J. Dakin suggested that biologists were 

 on the threshold of a new line of study of evolution 

 from the physico-chemical side. He believed that 

 the faculty of evolution was as much a character of 



the organism as irritability or reproduction, and 

 pointed out that natural selection was really natural 

 elimination, the production of characters being 

 inherent properties. 



Dr. A. B. Rendle said it was almost impossible 

 to say what characters were viseful or not, and, in 

 view of the limited space available, considered that 

 the multiplication of genera and species in geometrical 

 progression was unlikely. 



Prof. J. Stanley Gardiner agreed that evolution 

 was an inherent property of protoplasm, and raised 

 the question as to why forms of life died out. He 

 expressed approval of the main thesis of "Age and 

 Area." 



In reply, Dr. J. C. Willis pointed out that there 

 must be some reason for the uniformity of expression 

 as given in his statistical work. He accepted the 

 phrase " Natural Elimination " instead of " Natural 

 Selection." 



In concluding the discussion, Prof. H. H. Dixon 

 pointed out that both " Natural Selection " and 

 " Age and Area " were essentially truisms, but none 

 the less required explicit statement and demonstra- 

 tion. 



Effects of Local Conditions on Radio Direction-finding. 



HTHE methods used for finding the direction in 

 -^ which Hertzian waves are incident at a radio 

 station have now attained a high accuracy, the 

 maximum error being well under one degree. It 

 does not follow, however, that the methods give the 

 direction of the sending station to the same accuracy. 

 The waves sent out may have suffered reflections 

 from all kinds of conductors before they reach the 

 receiving station. Hence, especially at night-time, 

 the apparent direction generally differs very appreci- 

 ably from the true direction. A preliminary report 

 on this subject, communicated by the Radio Research 

 Board, was read on November 8 to the Radio section 

 of the Institution of Electrical Engineers by Messrs. 

 Smith-Rose and Barfield. They classify the causes 

 of distortion under two heads : First, those which 

 are vaguelv classed as night - effects and occur 

 between sunset and sunrise. They are sometimes 

 as large as 20 , and little is known as to their cause. 

 Hence in practice radio-direction finding is restricted 

 to day-time. The second causes of error are those 

 due to conducting substances in the immediate 

 neighbourhood of the search coil. In one experi- 

 ment a metal tube 50 ft. long, semicircular in 

 cross-section, and of radius 3 ft. 6 in. was used. 

 When the coil was at a distance of 15 ft. from 

 either end errors became appreciable, and when 

 placed 15 ft. inside the tube the error was as great 

 as 29 . 



Experiments were also made on board ship, as 

 radio-direction rinding is of great value in navigation. 



It was found that when the waves came fore-and-aft 

 or athwart the ship there was no error, but that in 

 intermediate positions the errors were sometimes as 

 great as 22 . As these errors are approximately 

 constant, corrections can be applied as in the case 

 of the magnetic compass. Curiously enough it was 

 found that underground metal work in the neighbour- 

 hood had a very appreciable effect on the apparent 

 direction of the incoming waves. The Aberdeen 

 University direction-finding station, for example, was 

 erected on what was thought to be a favourable 

 site. The errors found, however, indicated the 

 existence of a long strip of metal in the neighbourhood 

 in a definite direction. The authors investigated 

 the cause and found that a sewer in the neighbourhood, 

 which was in the given direction, was supported by 

 a strip of steel 6 ft. wide, 300 ft. long, and 8 ft. 

 below the surface. 



Overhead wires also caused appreciable but variable 

 errors, which the authors traced to" variations of the 

 telegraph and telephone circuits when in use. They 

 investigated the errors produced by tuned aerials 

 and trees. Trees when damp have small resistance, 

 and so the oscillations set up in them affect the 

 direction of the waves. A row of damp trees forms 

 a very good conducting screen. It was noticed that 

 the waves showed a tendency to move round large 

 conductors. Owing to variable meteorological condi- 

 tions a very large number of experiments had to be 

 made before definite results were obtained. The 

 authors are continuing theri investigations. 



New X-ray Department at Manchester. 



CIR HUMPHRY ROLLESTON, president of the 

 *--' Royal College of Physicians and of the Rontgen 

 Society, opened on November 18 the new X-ray 

 department of the Manchester Royal Infirmary, 

 which is probably the most completely equipped 

 department of its kind in this country. This has 

 been made possible by two separate gifts of 5000/., 

 one by Mr. Robert McDougall and the other by an 

 anonymous benefactor. 



The occasion coincided with a joint provincial 



NO. 2770, VOL. I IO] 



meeting at Manchester of the Rontgen Society and 

 the Electrotherapeutics Section of the Royal Society 

 of Medicine ; and a considerable number of members 

 took the opportunity of inspecting the new equip- 

 ment, which has been installed by Messrs. Watson 

 and Sons under the direction of Dr. A. E. Barclay, 

 senior radiologist to the Infirmary 



The new department is on the ground-floor, is well 

 lighted and ventilated, possesses generous head room, 

 and is cheerfully decorated, all features which are 



