March 17, 192 1] 



NATURE 



87 



the past ten years. Dr. Hankin has been able to 

 study under exceptionally good conditions during his 

 residence in India the circumstances which influence 

 the soaring flight of birds, dragon-flies, and flying- 

 fishes. In all cases the wings of the bird, dragon-fly, 

 or fish are more nearly horizontal the faster the flight, 

 and the speeds attained are very similar, i.e. from 5 to 

 10 metres per second for slow, and between 15 and 20 

 for fast, flight, whether of vulture, dragon-fly, or flying- 

 fish. The regularity of the soaring flight of cranes 

 in flocks disproves the theory which attributes it to 

 chance air-currents. Both dragon-flies and flying-fish 

 use their wings, legs, or abdomen as brakes during 

 soaring flight, and this use discredits the theory that 

 the flight is due to imperceptible wing movements, 

 which, if they existed, the bird or fish could diminish 

 at will. The horizontality of the wings disproves the 

 side-current theory, while observations of soaring in 

 the midst of aerial seeds or feathers which showed 

 no irregularity of motion render the theory of tur- 

 bulence untenable. Dr. Hankin thinks that direct 

 observation requires to be supplemented by experi- 

 ment before a satisfactory explanation of soaring 

 flight can be furnished. 



The Collected Researches of the National Physical 

 Laboratory (vol. xv.) is a reprint of eighteen papers 

 dealing with physical, metallurgical, and engineer- 

 ing subjects which have appeared in the pro- 

 ceedings of scientific societies or in the technical Press 

 during the years 1915-19. So many of these papers 

 are of great value that it is difficult to select any one 

 for special comment, but five by Dr. N. Campbell 

 alone or in collaboration with Mr. C. C. Patterson 

 illustrate so well the character of the scientific 

 and industrial problems which the laboratory 

 is called upon to solve that their nature may be 

 indicated. They deal first with the present theory 

 of the high-potential magneto, and show that it does 

 not yet furnish a sufficiently firm basis on which to 

 attempt improvements of the machine. They then 

 consider the nature of the spark at the break in the 

 primary of such a machine, and establish the fact 

 that it is in reality an arc. Lastly, they deal with 

 the effect of the spark discharge in igniting explosive 

 mixtures such as those used in gas- and oil-engines, 

 and show that the energy necessary to initiate an 

 explosion is much less than that supplied in practice 

 at the present time. At several points of the papers 

 it is intimated that the research has been discon- 

 tinued, and if this is the case it seems unfortunate 

 for the gas-engine industry. 



To facilitate the systematic testing of samples of 

 dust from coal-mines made necessary by the Act of 

 1920, Messrs. A. Gallenkamp and Co. are supplying 

 sets of apparatus (according to the designs of Mr. 

 S. R. Illingworth, of the School of Mines, Treforest) 

 which seem very well adapted for the purpose. 

 The drying is effected in an oven, similar to that 

 used by the U.S. Bureau of Mines, through which 

 dry air is drawn so as to chang^e completely the atmo- 

 sphere round the samples every six minutes, the 

 outer jacket containing water with 5 per cent, of 

 glycerine. The roasting dishes are of silica with 

 NO. 2681, VOL. 107] 



aluminium lids, and they are inserted at one end of 

 an electric muffle furnace so wound that the tem- 

 perature gradually increases from front to back to 

 prevent the coking of the freshly introduced samples. 

 The burnt samples are withdrawn from a door at the 

 back after they have stood for some time at the 

 full temperature of 800-850° C. The roasting dishes 

 stand on silica slabs, by which they are pushed in 

 and withdrawn from the furnace. A scheme of 

 weighing and heating two batches of samples alter- 

 nately is suggested whereby twentj-four samples 

 might be analysed by one chemist in a working day ; 

 if the apparatus enables this to be done^-and the 

 suggestion appears to be feasible — it will certainly 

 be an improvement on present practice. The scheme 

 of tests does not include the determination of carbon 

 dioxide in "carbonate" dusts. These dusts are 

 coming into use, and a small addition to the ap- 

 paratus for this purpose might be desirable. 



Mr. R. D. Duncan, of the Radio Engineer Signal 

 Corps of the U.S. Army, contributes a valuable paper 

 on "wired radio" to the Journal of the Franklin 

 Institute for January. By "wired radio" is meant 

 simply the use of high-frequency currents superposed 

 on ordinary telephone or telegraph lines to transmit 

 speech or signals without interfering with the normal 

 working of the line. One of the reasons for originating 

 this research in America was an attempt to utilise 

 the large quantity of radio-telephone apparatus which 

 had been purchased during the war. One advantage 

 of this system is that speech distortion, which causes 

 so much trouble in long-distance wire telephony, is 

 practically eliminated. The attenuation also is much 

 less than had been anticipated. A very interesting' 

 and important application of the method is for estab- 

 lishing communication with a train in motion. Ex- 

 periments carried out on the New York Central Rail- 

 way are described. The telephone conductors which 

 run parallel to the railway track were used to carry 

 the high-frequency currents, and at the fixed station 

 the transmitting and receiving apparatus were con- 

 nected between the aerial wire and the earth. In the 

 moving train the apparatus was connected to a closed 

 loop which was placed at the proper angle to the 

 plane of the telephone wires. Employing this system 

 and using a high-frequency power of only two watts, 

 excellent telephony was obtained up to a distance of 

 ninety miles. It was noticed that the signals received 

 in the train varied periodically in intensity when it 

 was in motion. This phenomenon was traced to the 

 existence of "standing waves" on the telephone 

 line. 



Engineering for February 18 contains a communica- 

 tion from the Metropolitan-Vickers Electrical Co., 

 Ltd., which gives an explanation of the causes lead- 

 ing to the breakdown of a new 15,000-kw. turbo- 

 alternator at Dalmarnock Station, Glasgow. The 

 insulation on the windings at one end of the machine 

 took fire on December 8, and the whole insulation 

 on this end was destroyed. Another generator was 

 nearly ready, and was installed and set to work one 

 week later. After running for a week sparks were 

 seen issuing from the top of the stator frame, and 



