298 



NATURE 



[November ii, 19 15 



persons, or 165 gallons per head, which is a very 

 liberal allowance compared with the customary con- 

 sumption of large towns in this country. The figure 

 is stated to include considerable quantities used by 

 mines, railroads, and other industrial concerns, but 

 even then it is greatly in excess of the standard pre- 

 vailing in the United Kingdom. B. C. 



ENGINEERING AT THE BRITISH 

 ASSOCIATION. 



SECTION G (engineering) had a very full pro- 

 gramme, which necessitated carrying the meet- 

 ing on until mid-day on Saturday, September 11. The 

 papers were grouped as follows : after the president's 

 address by Dr. Hele-Shaw on Wednesday, the morning 

 was devoted to papers dealing with thermodynamics. 

 The following morning was set apart for papers by 

 local engineers, describing recent work in the various 

 departments of municipal engineering (electric, gas, 

 drainage, etc.) ; the papers read on Friday were all 

 connected with electrical engineering, while Saturday 

 morning was devoted to mechanical engineering. 



Wednesday, September 8. — In his address the presi- 

 dent insisted on the duty of the British Association to 

 justify its existence by doing- something- tangible to 

 help the Empire in the great industrial struggle which 

 must ensue when the military struggle comes to an 

 end. He advocated the formation of a committee, 

 initially of the engineering section, not merely to offer 

 Its services to any Government department, but to 

 consider and urge the initiation of those reforms 

 which would strengthen our hands in the coming 

 international industrial warfare. The first paper was 

 by Profs. Asakawa and Petavel, describing a series of 

 experiments on the efficiency and losses of a gas 

 engine; a preliminary note on the subject was pre- 

 sented at the Birmingham meeting- two years ago. 

 The authors have determined the overall efficiency 

 and the magnitude of the various losses with different 

 mixtures and different compression ratios. The 

 highest overall efficiency obtained was 27-4 per cent. 

 The mechanical losses were determined by the rate of 

 change of the kinetic energy of the rotating parts, as 

 is very commonly done in testing electric motors. 



Prof. W. M. Thornton gave two short papers of a 

 theoretical and speculative nature, entitled "The Total 

 Radiation from a Gaseous Explosion" and "The 

 Change of the Specific Heat of Gases with Tempera- 

 ture." According- to the author, the lost pressure or 

 suppressed h^at of a gaseous explosion can be ex- 

 plained mechanically by considering- two combining 

 atoms to act like colliding spheres. Their translational 

 energy will generally be converted partly into vibra- 

 tional and partly into rotational energy. Assuming 

 that before the collision the translational and rotational 

 energies of the atoms were equal, and that on collision 

 the former is equally converted into rotational and 

 vibrational, the latter, on which depends the radiation, 

 will represent 25 per cent, of the total, which result 

 the author claims to be in agreement with the obser- 

 vations of Hopkinson and David. 



On Wednesday afternoon at the laboratories of the 

 Manchester Steam Users' Association, Mr. C. E. 

 Stromeyer explained and demonstrated a machine for 

 determining the fatigue limits calorimetrically. In 

 this machine the specimen, which is subjected to 

 rapidly reversed torsion, tension, or bending stresses, 

 is water-jacketed, and the temperature of the water 

 passing through the jacket is measured on entering 

 and on leaving-. No difference is detected until the 

 stress reaches the fatigue limit for the specimen under 

 test, but as soon as this is passed, heating of the 



NO. 2402, VOL. 96] 



jacket water takes place. Hence the fatigue limit is 

 determined by gradually increasing the stress and 

 watching the two thermometers. 



Mr. Stromeyer also gave a demonstration of the 

 phenomenon of water hainmer by means of gas-heated 

 glass vessels and tubes. 



Thursday, September 9. — Mr, de Courcey Meade, 

 the corporation engineer, read a paper on the Man- 

 chester drainage scheme, and showed a number of 

 lantern slides illustrating the special work in con- 

 nection with the new sewers now under construction. 

 He was followed by Mr. S. L. Pearce, the corporation 

 electrical engineer, who outlined the growth of the 

 electrical undertaking and then described the general 

 outlines of the projected station at Barton on the 

 Bridgewater Canal. When completed, this station, 

 which at present exists on paper only, will be one 

 of the largest in the country. It will transmit three- 

 phase power at 33,000 volts to a number of sub- 

 stations. An interesting point is that the site is in 

 close proximity to the corporation sewage works at 

 Davyhulme, and it is proposed to use the purified 

 effluent for condensing purposes, the canal authorities 

 having refused permission to use the canal water. 

 The increased temperature of the sewage effluent 

 after passing- through the condensers is advantageous 

 in the further treatment before final discharge. 



Prof. A..B. Field described the special research work 

 which is being carried out in the mechanical engineer- 

 ing- department of the Municipal School of Tech- 

 nology, which was afterwards visited by the members 

 of the Section. 



The corporation gas engineer, Mr. J. C. New- 

 bigging, described the improvements recently intro- 

 duced by the adoption of automatic vertical retorts ; 

 he also attacked the system of applying the profits 

 from municipal gas undertakings to the relief of 

 rates, instead of lowering the price of gas and thereby 

 increasing its adoption for heating and power pur- 

 poses. It need scarcely be said that this part of his 

 paper did not go unchallenged in the discussion, 

 dealing, as it does, with one of the thorniest problems 

 of municipal politics. 



A paper was read by Mr. E. C. Mills, describing 

 his producer for placing in front of an ordinary steam 

 boiler. The gasification of the fuel is carried out in 

 this external producer, while the combustion of the 

 gas takes place inside the ordinary boiler flue. Slides 

 were shown and actual test figures given for boilers 

 which had been fitted with the apparatus. 



Friday, September 10. — Mr. N. W. McLachlan 

 showed experimentally the rapid heating of iron strips 

 when magnetised by high-frequency currents obtained 

 from an arc-generator. The variation of perme- 

 ability with temperature and the points of recales- 

 cence could be traced in the variation of the current 

 taken by the magnetising coil. The phenomena are 

 complicated, however, by the skin effect, the depth 

 of penetration varying with the temperature due to 

 the changes in both resistance and permeability. 



A self-adjusting commutating device was described 

 by Prof. Miles Walker, in which each brush is divided 

 into two, one in advance of the other, the two being 

 lightly insulated from each other. Before combining, 

 the current from one brush passes round the inter- 

 pole winding, while that from the other passes through 

 an equivalent resistance. If the commutation be 

 perfect, the current density will be uniform over the 

 whole brush contact surface, and each brush will 

 collect half the total current ; if, however, on account 

 of saturation at heavy loads, the strength of 

 the interpole be insufficient, the commutation will 

 be so affected that a larger share of the total current 

 will pass through the interpole winding, increasing- 



