43S 



NA TURE 



[August 30, 1894 



Sir Frederick Bramwell's paper was one of considerable 

 interest, the veteran engineer described the experience of his 

 youth when he was a proicgt- of Hancock, who was then running 

 a steam carriage for ordinary purposes of carr)ing passengers on 

 the public roads. Sir Frederick stated how he used to travel from 

 work to his home when an apprentice, Hancock generally giving 

 him a lift on his return journey with the steam carriage. Under 

 the existing state of the law steam locomotion of this nature is, 

 of course, an impossibility, the restrictions which have been put 

 on this method of transportation being absolutely prohibitive. 

 These restrictions were brought about in conseiiuence of the in- 

 troduction of traction engines, as we now see them on our 

 country roads. The pace of steam-propelled vehicles is limited 

 to three miles an hour, and it is necessary that a man should 

 walk in front of the engine with a red flag ; naturally such regu- 

 lations make the carriage of passengers out of the question. 



This is much to be regretted, for steam carriages, as has lately 

 been proved by continental experience, can be made both safer 

 and more expeditious than those drawn by horses. They are 

 more under control, being easily stopped and turned, and they 

 are naturally far cheaper. 



To return, however, to Sir Frederick Bramwell's paper, the 

 details of the early road steam carriages possess considerable in- 

 terest at the present time, as pipe boilers were used in nearly 

 all of them, and now that the water-tube boiler is coming to the 

 front so rapidly, it is interesting to see what was done by 

 the pioneers of steam engineering. Many inventors whose 

 brains are active in this field would do well to study the earlier 

 records, for old types are now being reinvented at an expendi- 

 ture of much useless brain work and anxiety. 



The second day of meeting of Section G [Friday, August lo^ 

 was a very busy one, a joint sitting having been arranged with 

 Section A. Four subjects were down for discussion, as stated 

 in the above list of papers. 



Prof. Henrici's contribution was one of great interest, as also 

 was Mr. Mallock's note on the behaviour of the rotating 

 cylinder. Lord Kelvin also gave a valuable lecture on the 

 resistance of solids moving through fluids. 



Public interest, however, was chiefly centred in the paper 

 read by Mr. Maxim, in which he described his tlying machine. 

 To hear this part of the transactions a large number of 

 members flocked into the hall, many of them being ladies. Some 

 of the members present did not appear to take much interest in 

 the more abstruse subjects dealt with by the previous lecturers, 

 and their want of attention made it a little difficult to follow 

 the first three speakers. 



Two papers, relating purely to Section G, were taken on this 

 day ; the first was Pro(. Fidler's monograph on the extensi- 

 bility of iron and sleel, a valuable contribution which, how- 

 ever, was read to a very thin audience. 



The author pointed out that the stress-strain diagram of 

 ductile material as autographically drawn does not indicate any 

 definite relation between tensile stress and plastic strain. The 

 unit stress varies in different pans of the bar ; the elongation 

 measure by the diagram being that of the whole bar. The 

 author's experiments indicated that the plastic extensibility 

 under any given stress is nearly the same in all segments of the 

 bar's length, even when the ultimate elongation varies. Volu- 

 metric measurements of the successive segments indicate that 

 there is no sensible telescopic shear, and justify the general 

 application of the assumption of unchanging volume. It 

 might at first sight be supposed that a bar of uniform plastic 

 extensibility ought to draw out unilormly over its whole length, 

 bat beyond a certain critical point a uniform extension is almost 

 impossible. In order to illustrate these points in a bar of mild 

 steel a diagram had been prepared. The law of pl.islic 

 extension is dcicrmlned by the curve, fixed malhematically the 

 curves of the plastic limit, and it fixed also the breaking 

 weight per square inch of original area. In regard to the 

 possibilities of deformation in a bar of nearly uniform extensi- 

 bility, as the plastic limit is approached the slightest irregularity 

 in section or in extensibility tends to precipitate the formation 

 of a contracted region, and beyond that limit the further 

 extension of the bar and the further contraction of arc will 

 be confined to the same region. For stresses below the plastic 

 limit the probabilities of deformation might be examined by 

 considering the relative time rates of extension at two elemenls 

 which may have been unequally stretched, anil at first the 

 tendency is theoretically in favour of preserving the cylindrical 

 form of the bar. Kut l>eyond the plastic limit these conditions 



are reversed, and the tendencies are all in favour of precipitat- 

 ing the most rapid contraction of area at the point where any 

 contraction already exists. Referring to the yield-point, ^uddcn 

 elongation takes place at different stresses in the different seg- 

 ments, while in any one short element it seems to be instan- 

 taneous. If the yield is arrested midway and the bar examined, 

 it may be found that the elong.-ili.in has been completed in 

 some segments and not commenced in others. 



In the discussion which followed. Profs. Unwin, Ewing, and 

 IleleShaw and Sir Benjamin Baker look part. Prif. Hele- 

 Shaw pointed out that certain bronzes, unlike steel, would 

 contract in sever.il places at once. 



Mr. Fitzmaurice's paper on the Blackw.ill Tunnel gave an 

 interesting description of that important work, now being carried 

 out under Mr. Binnie, for the London County Council. 



Two papers only were read on Saturday of the meeting. 

 The first an extremelv interesting contribution by Sir Andrew 

 Noble, of Elswick. The author referred to the early experiments 

 of Count Rumford to asceriain the pressures in the bores of 

 guns, and pointed out the errors into which that investigator 

 was led. He referred to the researches of Robins, Cavalli, 

 Rodman, and those of the Prussian Artillery Comuiittee of 

 1S54 He also gave details of experiments made by himself, 

 from which it would appear that with projectiles of increasing 

 weight very different results are obtained, in regard to pressure, 

 with modern slow-burning powders than with the older fine 

 grain powders. 



Mr. Bryan Donkin's paper was also one of considcr.tble 

 interest, and gave details of an extensive series of experiments 

 made by the author. He pointed out that in most cases 

 cylinder walls of engines are much colder than the steam, and 

 often one-half the weight of steam is condensed during admis- 

 sion. The details of this will be published later, and at greater 

 length, in the Proceedings of the Institution of Mechanical 

 Engineers. It m.iy be said generally, that throughout the 

 experiments an increase of economy with hotter walls was 

 always verified. 



On Monday the proceedings were largely devoted, according 

 to custom, to electrical engineering. 



Mr. Preece's paper, on .signalling through space, was of a 

 very popular nature, and attracted a large audience. He 

 described the operations which took place at Kilbrannan Sound. 

 It is satisfactory to know that the Post Office aulhorilies are 

 introducing metallic returns wherever possible for telephone 

 circuits. 



Prof. Sylvanus Thompson's paper was in praise of alternate 

 currents. The author expressing his opinion that the alternate 

 current system would entirely supersede continuous currents for 

 lighting and power dislriliution purposes. The continuous 

 current being superior for electrolytic purposes alone. Mr. 

 Picece supported the paper, whilst Prof. Kennedy and Mr. T. 

 Parker took entirely ditlerent views. j 



Mr. Parker's paper was an excellent description of the 

 electric lighting in the city of Oxford. Mr. Lea described a 

 special form of chronograph he had had made to his own 

 designs. Mr. Clark's paper w.is also one of value, and should 

 be studied in the original by those interested in the measure- 

 men' of high temperatures. 



Tuesday's proceedings commenced with the reading of the 

 Report of Prof. Unwin, of the Committee on the Dryness of 

 Steam. This is a long and valuable report, but as it will , 

 appear in full in the Transactions of the Association, it is not 1 

 necessary we should deal with it on the present occasion. 



Mr. Burstall, in his paper, and by aid of a model which he 

 exhibited, has given a new means of illustrating the temper.atutc 

 entropy diagram. This model will doubtless he seen on future i 

 occasions. Considerable ingenuity has been shown in its con- 

 struction. Mr. .Swinburne's paper w.is one of practical interest ^ 

 to engineers, whilst Prof. Capper's contribution on the calibra- 

 tion of laboratory instruments will prove of value, and is worthy 

 of passing notice. The author stated that the reliance to be 

 placed upon observations made with measuring instruments 

 evidently depends upon the accur.icy with which those instru- 

 ments record. Neglect of this fundamental truth often leads to 

 inaccurate and erroneous deductions from experinienis which 

 arc themselves of the highest scientific value ; not infrcijuently 

 the whole value of oliservations maybe destroyed by insufficieilt 

 care in the calibration of the insiruments used. The subject i!| 

 therefore one of some importance. The author described ihti 

 chief sources of error in some of the most common engineerinf 



NO. 1296, VOL. 50] 



