August 14, 19 19] 



NATURE 



467 



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may be assured that they will find every con- 

 venience and comfort immediately at hand. Only 

 in the problematical case of an exceptionally large 

 sectional meeting- will it be necessary to make use 

 of another building. 



It is unnecessary in this article to describe in 

 detail the long programme of work, a copy of 

 which can be obtained from the headquarters of 

 the association. The journal, giving full particu- 

 lars, will, as usual, be issued daily throughout 

 the meeting. The general public will probably be 

 most interested in the papers and discussions 

 relating to scientific work in the war, on such 

 subjects as tanks, submarine mining, the para- 

 syane, air photography, the progress of aviation, 

 airships, and directional wireless. Of special 

 topical interest will also be the discussions ar- 

 ranged by the Economics Section on the National 

 Alliance of Employers and Employed, price-fixing, 

 with special reference to Australian experience, 

 transport, iinance and taxation, and the gold 

 standard ; by the Agriculture Section on war-time 

 food production ; by the Physiology Section 

 (jointly with that of Economics) on the influence 

 of the six-hour day on industrial efficiency and 

 fatigue ; by the Education Section on various 

 problems of modern education ; and by the 

 Geography Section on long-distance air routes, 

 the geography of Imperial defence, frontiers in the 

 East of Europe, and the colonisation of Africa. 



Following the precedent set in Birmingham in 

 1913, citizens' lectures will be delivered in out- 

 lying parts of the town during the week, in co- 

 operation with the Workers' Educational 

 Association. These will comprise lectures by 

 Prof. H. H. Turner on "Modern Astronomy," 

 Prof. S. H. Reynolds on " Purbeck Isle and its 

 Geology and Scenery," and Prof. J. L. Myres on 

 " Woman's Place in Nature from an Anthro- 

 pological Point of View." 



Numerous excursions will be made to places of 

 interest in the neighbourhood. The Engineering 

 Section will, by special permission of the Ad- 

 miralty, visit the Royal Naval Cordite Factory at 

 Holton Heath, a vast organisation which has 

 sprung up during the war, and will also inspect 

 the Bournemouth and Poole Gas and Water 

 Works and the power stations of the tramways 

 and electric light undertakings. The Geology 

 Section will journey each afternoon to points of 

 geological interest in the locality, including such 

 favourite haunts of geologists as Lulworth Cove 

 and Kimmeridge. The Botany Section will find 

 much material for work and discussion in the 

 New Forest, at Shell Bay, and elsewhere. The 

 Agriculture Section is arranging a visit to Iwerne 

 Minster, in the neighbouring county of Dorset; 

 while the Anthropology Section will organise an 

 excursion to the Channel Islands if sufficient 

 names are received before the meeting. Com- 

 munications on the last-named subject should be 

 addressed to Dr. R. R. Marett, Exeter College, 

 Oxford, who is to read a paper on recent dis- 

 coveries of archaeological Interest in the Channel 

 Islands. 



NO. 2598, VOL. 103] 



It may also be mentioned that Lord Montagu 

 of Beaulieu, president of the Conference of Dele- 

 gates of Corresponding Societies, has offered to 

 show members and their friends over the beau- 

 tiful Beaulieu Abbey, with its thirteenth and four- 

 teenth century remains ; and Sir Merton and Lady 

 Russell Cotes have consented to throw open to 

 them the East Cliff Hall and its fine collection of 

 art treasures. 



From the social point of view, those attending 

 the meeting will find the Bournemouth week a 

 very pleasant one, even though official functions 

 on a large scale are not contemplated. Various 

 local clubs and institutions will be ready to receive 

 them as honorary members during the period of 

 the meeting, and in other ways a great deal will 

 be arranged in the way of hospitality and 

 entertainment. 



SUBMARINE ACOUSTICS. 



THE war has been responsible for great 

 developments in many branches of science. 

 As a consequence of the submarine menace, close 

 attention has been given to the subject of marine 

 physics, with the result that notable advances 

 have been made in several directions, especially 

 in that of submarine acoustics. Much of what has 

 been accomplished is still regarded as confidential 

 information, but some interesting disclosures have 

 recently been made by Prof. W. H. Bragg in the 

 Tyndall lectures delivered before the Royal 

 Institution, and in a lecture at the British Science 

 Guild's Exhibition at Westminster. 



The singular property which distinguishes a 

 submarine from other ships is its capacity of 

 rendering itself invisible when pursued or when 

 seeking and attacking its prey. Robbed of this 

 power, it is an extremely vulnerable craft, and 

 falls a ready victim to more heavily armed and 

 armoured surface ships when once its presence 

 has been detected and its position located. 



The acoustic method of detecting a submerged 

 submarine moving in the open sea was found to 

 be far more sensitive and to give a much longer 

 range than all other methods. Instruments used 

 for this purpose are called hydrophones. Many 

 varieties of hydrophone have been evolved and 

 perfected, but by far the largest class consist 

 essentially of a microphone attached to a dia- 

 phragm which forms one wall of a watertight 

 cavity. The microphone is connected through a 

 suitable electrical circuit to ordinary telephone 

 receivers, the complete installation resembling a 

 unit of an ordinary- land telephone system. In 

 use the hydrophone is suspended from the bul- 

 warks of a stationary ship, or mounted in tanks 

 attached to the hull, or trailed behind in a suitable 

 "fish " body in the case of a moving ship. The 

 range of a hydrophone depends upon the size and 

 speed of the source of sound, the depth and state 

 of the sea, the presence of other sources of sound, 

 etc., and may vary from a few hundred yards to 

 several miles. 



The difficulty of ascertaining the direction of 



