July 17, 1919] 



NATURE 



393 



encouraging collection of definite products, the manu- 

 facture of which on a large scale has been made 

 possible in the British factories during the last five 

 years, when the chemical skill and energy available were 

 largely absorbed in the business of making explosives 

 and other war material. This is very satisfactory, but 

 the applications of chemistry, apart from the manu- 

 facture of definite products, must not be overlooked. 

 Examples of such application are to be seen on every 

 side, in metallurgy, in agriculture, in physiology and 

 medicine, in the treatment of water, and in sanitation. 



Sir William Tilden concluded his lecture by point- 

 ing out that one great feature of modern chemical 

 manufacture is the production by synthetic processes 

 of compounds which hitherto have been derived from 

 natural sources. Of these the most remarkable is the 

 production of ammonia by combination of hydrogen 

 with atmospheric nitrogen, which, notwithstanding the 

 physical difficulties, is likely to proceed on a very large 

 scale. Another case of a different kind is the pro- 

 duction of rubber which has been going on in Ger- 

 many during the war. There can be no doubt that in 

 a few years this substance will appear on the market 

 provided the initial material, at present acetone, is 

 available at a sufficiently cheap rate. Synthetic 

 rubber now obtainable in the laboratory costs about 

 twenty times as much as the natural article from the 

 plantation. 



In his lecture on July 8 on the .subject of trans- 

 mitting and picking up sounds in water. Prof. VV. H. 

 Bragg first made clear the great difference between 

 the noisy air-world above the sea and the quiet, almost 

 soundless world below the waves. This is all the more 

 remarkable in view of w^ater being a much better 

 carrier of sound than air. Being specially engaged 

 during the war on an investigation of submarine 

 sounds, he had visited the Zoo to study fishes and their 

 hearing or sounds produced by them. Their powers 

 were, however, found to be so deficient as to suggest 

 that lack of noise in their movements under water 

 had rendered acute hearing valueless to the fish in its 

 struggle for existence, either as the hunter or the 

 hunted. By means of gramophone records, lent by 

 the Admiralty, Prof. Bragg showed how the silent 

 submarine world was disturbed by the movements of 

 ships or bv the breaking of waves on the coast, and 

 how difficult it was, among the loud noises made by 

 neighbouring propellers, to distinguish the faint sounds 

 caused bv a submarine. The hearing of these was the 

 real object in view, and a record of the German sub- 

 marines entering Harwich was used to show their 

 special character. 



Some of the means used for locating the source of 

 the sounds were also described, and a full-sized 

 " hydrophone " was shown, consisting of a diaphragm 

 carried in a heavy iron ring and shielded on one side 

 bv a special plate of xylonite enclosing several air- 

 cells, which so blocked the sound-waves coming in 

 that direction as to form the equivalent of turning a 

 deaf ear in one direction. Lantern-slides were shown 

 taken from kinema-films which illustrated graphically 

 the vibrations received by a microphone placed at the 

 centre of such a shielded diaphragm. Prof. Bragg's 

 explanation of the films led to a most interesting 

 deduction as to the post-war value of these investiga- 

 tions. , He showed a film on which appeared six 

 parallel records of receiving galvanometers represent- 

 ing thf> conditions at six different stations. Each 

 station was equipped with such a hydrophone and 

 connected up electrically to the galvanometer, which 

 recorded their vibrations on the film as lines, which 

 in this case remained perfectly even until a destroyer, 

 sent straight out to sea for the purpose, exploded a 

 depth-charge. As the sharp sound-wave sent out 



NO. 2594, VOL. 103] 



thereby reached each hydrophone, the corresponding 

 line broke up into oscillations, and the moment at 

 which these oscillations began was clearly indicated 

 to a thousandth of a second by their position on the 

 film, giving the exact time of arrival of the sound- 

 wave at each hydrophone. The speed of sound in 

 water being also well known, the position of the ship 

 at the time of each explosion could therefore be ascer- 

 tained. 



The greatest distance recorded on the film was 

 seventy-five miles, but the undiminished accuracy of 

 its indications proved , that the method of locating 

 ships at sea would be successful at much greater dis- 

 tances, and at the present time it has been developed 

 up to a range of 230 miles, with no sign of falling off 

 in its efficiency. On shorter distances it has been 

 found possible to signal with a simple detonator 

 instead of the 40-lb. charge used in the first experi- 

 ments. These preliminary successes open up a most 

 promising field of practical applications, especially in 

 coastal surveys and the exact location of rocks and 

 shoals. At present it is being largely used in the 

 North Sea, several stations being at work on the 

 east coast of Britain. It has also been successfully 

 used for the exact location of ships and aircraft during 

 fog. 



The lecture on "Coal Conservation" given by 

 Prof. H. E. Armstrong on Friday, July 11, was a 

 protest against the legislation foreshadowed in the 

 Electricity Supply Bill now before the House of 

 Commons as^ both premature and narrow, and a plea 

 for a complete inquiry into the uses of coal, with the 

 view of co-ordinating the various interests and the 

 ultimate comprehensive treatment of all the industrial 

 issues. Prof. Armstrong favours the production of a 

 smokeless fuel, with the object of abolishing the 

 smoke nuisance and also of saving the valuable vola- 

 tile products which are wasted in burning raw coal. 

 He would therefore have the use of raw coal entirely 

 disallowed in the near future ; In view of the prospec- 

 tive world-shortage of petroleum, it will be criminal 

 folly if we fail to produce all the oil-fuel that it is 

 possible to obtain by subjecting coal to a preliminary 

 distillation at a relatively low temperature. He is an 

 advocate of the establishment, at least in the larger 

 towns, of fuel and power centres charged with the 

 supply of all the forms of fuel and power required by 

 the public within their areas. Coal should be car- 

 bonised at these centres in such a way as to secure the 

 recovery of the maximum proportion of by-products, 

 which might be in part distributed and in part 

 further utilised at the centre in generating electric 

 current. The advantages attending the use of an 

 easily combustible solid fuel instead of gas as a 

 domestic heating agent were insisted upon. In the 

 subsequent discussion this recommendation w-as 

 strongly supported by Prof. Bone, who spoke against 

 the suggested provision of gas-heating appliances alone 

 in the improved dwellings which it is contemplated to 

 provide for the use of the masses. Whilst suitable for 

 kitchen and occasional use, gas is not only much 

 more costly than solid fuel but also a far less healthy 

 means of heating dwelling-rooms over any consider- 

 able period. The scheme suggested would render pos- 

 sible the supply of a heating gas of higher quality* 

 than is now contemplated by the gas interests; for if 

 the whole of our bituminous coal were carbonised at 

 a low temperature, a large amount of rich gas would 

 be produced which would J)ear dilution with "water- 

 gas " and yet be superior as a calorific agent to that 

 which the gas companies can provide in existing 

 circumstances. The advantages the scheme has are 

 such that, ere long, electricity should entirely supplant 

 gas as an illuminating agent. 



