442 



NATURE 



[August 2, 191 7 



would give some support to Murray's theory of 

 bipolarity had not the evidence against it by the 

 rest of the Antarctic fauna been overwhelming. 

 He also furnishes further evidence that some aren- 

 aceous foraminifera select the material for their 

 shells, since Reophax spiculifera rejects sand 

 grains and uses only sponge spicules, which it 

 builds up into funnel-shaped chambers. Mr. 

 Chapman's most interesting Antarctic fossil is a 

 Cambrian calcareous alga, which he has referred 

 to Bornemann's genus Epiphyton from Sardinia 

 as a new sf>ecies, E. fasciculatum. 



The rest of the volume consists of a series of 

 petrologic reports by Messrs. Jensen, Allan Thom- 

 son, Benson, Walkom, Woolnough, Skeats, and 

 Cotton, Sir Douglas Mawson, and Miss Cohen. 

 Dr. Jensen describes some samples of Antarctic 

 soil on which, though due to mechanical disinte- 

 gration rather than to chemical decay, plants were 

 found to grow when kept adequately warm. Dr. 

 Jensen also contributes a chapter on the interest- 

 ing alkaline rocks of Mount Erebus, and discusses 

 the classification of the kenytes and their relations 

 to the trachydolerites. Dr. Allan Thomson has 

 carefully investigated some inclusions in the 

 trachytes and kenytes, and founded for one series a 

 new rock type, microtinite , so called as they are 

 aggregates of plagioclase felspars. He discusses 

 the terminology of included rock fragments, and 

 adopts Lacroix's terms " homoeogenous " and 

 "enallogenous " as the best yet proposed. 



The volume has an excellent index to both 

 volumes. Mr. Dun's promised bibliography of 

 Antarctic geology has been postponed, but its early 

 publication would be a great boon, as the subject 

 has now a very scattered literature. 



RADIO-MECHANICS. 

 Radio-dynamics: The Wireless Control of Tor- 

 pedoes and Other Mechanisms. By B. F. 

 Miessner. Pp. v + 206. (London : Crosby 

 Lockwood and Son, 191 7.) Price 95. net. 

 ' I '"HIS little volume deals with a subject of con- 

 ■*- siderable interest at the present time, viz. 

 the control of torpedoes or other vessels of war by 

 means of electromagnetic waves. The author has, 

 however, unnecessarily increased the bulk of his 

 book by the introduction of a good deal of irrele- 

 vant matter, and by space given to elementary 

 facts- connected with wireless telegraphy which 

 might quite well have been taken as familiar to 

 any reader likely to be interested in it. Moreover, 

 he has rather overestimated the importance of the 

 early work of some American investigators, such 

 as Dolbear and Tesla, and done insufficient justice 

 to that of European workers, such as Marconi, 

 Fleming, Lodge, Muirhead, E. Wilson, and 

 others. Too much space is given to the descrip- 

 tion of methods of communication, such as those 

 of earth conduction, ultra-violet light, and infra- 

 red rays, which have, never become practically 

 useful. 



The proi>er discussion of apparatus for the con- 

 trol of mechanism at a distance by means of 

 electromagnetic waves does not begin until chap. 

 •\*n o/iro ■\rrtr nn~I 



xi., p. 78, of the book, and even then the treat- 

 ment is of a rather sketchy character. The essen- 

 tial principles involved are quite easy to under- 

 stand. A torpedo or other vessel to be directed 

 must have on it some source of motive power 

 such as storage cells, compressed air, or a petrol 

 motor. This power drives the screw propeller and 

 moves the vessel. Also the same source of power 

 is used to put the helm to port or starboard or 

 straight. We have then to set in motion some 

 motor or gearing which starts or stops the driving 

 power, or engages or changes the mechanism for 

 steering. The boat is, therefore, provided with 

 a mast carrying an aerial wire or antenna, by 

 means of which electrorhagnetic waves, sent out 

 from a shore station are absorbed. The feeble 

 electric currents thus set up in the aerial wire are 

 utilised to set in motion a sensitive relay, and this 

 in turn has to control the power which steers or 

 propels the boat. 



The first difficulty is the nature of the radiation 

 detector which is connected to the antenna. In 

 the early days of wireless telegraphy this was 

 always some form of coherer, generally the 

 metallic-filings coherer of Branly as modified by 

 Marconi or Lodge. This detector is, however, 

 rather uncertain in action an3 requires the addition 

 of an automatic tapper to bring it back to the 

 sensitive state after it has received and responded 

 to a signal. Hence of late years it has been 

 entirely ousted as a wave detector by more certain 

 appliances, such as Marconi's magnetic detector, 

 the Fleming vacuum valve, or some form of 

 crystal detector. These modern detectors operate 

 with or control such small alternating currents that 

 they cannot with certainty set in action any electro- 

 magnetic relay capable of being used on board a 

 small vessel at sea. 



The first difficulty, therefore, in connection with 

 the mechanism of radio-directed vessels is the 

 selection of a suitable wave detector and of a 

 relay. The author found that a form of Lodge- 

 Muirhead self-acting coherer, called the steel- 

 wheel coherer, was a useful one, and he con- 

 structed a suitable relay by modifying a type of 

 movablcrcoil galvanometer. Even when such 

 arrangements are perfected so that the sending 

 out of electromagnetic waves which impinge on 

 the torpedo aerial can be made to steer it by setting 

 in action some mechanism whFch throws over the 

 rudder to one side or the other, there still remains 

 the difficulty of rendering the radio-receiver 

 immune to vagrant electric waves or to intentional 

 attempts to mis-steer the boat on the part of an 

 enemy. 



The reader will find in chap. xiv. an account of 

 the work done in attempts to develop a radio- 

 steered torpedo at the laboratory" of Mr. John 

 Hays Hammond, jun. In chaj>s. xv. and xvi. the 

 difficulties connected with control and interference 

 are discussed. 



Although small vessels have been controlled in 

 this manner by electromagnetic waves up to a dis- 

 tance of ten miles or rather more, the practical 

 problem of certain control cannot be said to have 

 been solved. The present book deals, therefore, 



