Septemlek 23, 1897J 



NA TURE 



507 



The photographs show that in the tin-antimony-copper (tin 

 being in large excess) the copper-tin in the form of needles or 

 plates crj-stallises out quite separately and independently of the 

 antimony-tin compound which exist as cubes, and both occur 

 side by side in the same alloy. A similar thing occurs with the 

 tin-antimonyphosphorus alloys, the plates of phosphide of tin, 

 and the cubes of antimonide of tin being clearly separate. The 

 eutectic of magnolia metal (lead 80 per cent., antimony 15 per 

 cent., and tin 5 per cent.), under high magnification presents 

 a very beautiful structure, quite different from that of lead and 

 antimony alone, and the fine delicate structure (Fig. 2) appar- 

 ently consists of crystallites of the cubic system, and these 

 possibly are a combination of the three metals present. 



The structures of the tin-antimony-arsenic alloys are very 

 remarkable, and evidently the crystals formed consist of what 

 might be called tin-antimony-arsenides, for they all crystallise 

 together in a fusible eutectic. The alloy, containing tin 75 per 

 cent., antimony 20 per cent., arsenic 5 per cent., presents a 

 most interesting appearance (Fig. i) ; the sections of the white 

 crystals are of more or less perfect circular form, and in the solid 

 alloy they exist as spheres, the fractured surfaces proving this 

 to be the case. 



Micro-metallography is a comparatively new science, the 

 borders only of which have been but slightly studied, but it 

 promises to give results of the highest scientific interest. 



MECHANICS AT THE BRITISH 

 ASSOC I A TION. 

 pERHAPS the most noteworthy feature in the work of this 

 section (G) was the prominence of the Canadian and American 

 papers, apart from the interesting and suggestive address of the 

 President on the education of engineers of the present day ; but 

 little of interest was contributed by the English members who 

 attended the meeting. Many members, who in past years have 

 done so much for the section, were unable to be absent from their 

 professional duties for so long a time as attendance at Toronto 

 necessarily involved. 



The first paper after the President's address to the section 

 was one by Mr. T. Munro, a Canadian engineer, describing the 

 great works the Canadian Government are constructing to 

 secure the carrying trade from the West, by canalising the 

 rivers between Montreal and Lake Erie wherever the rapids in- 

 terfere with trafific. The traffic has grown so enormously since 

 the construction of the trans-continental line of the Canadian 

 Pacific opened up the great western plateaus for settlement, that 

 the older systems of canals are practically useless. The actual 

 piece of work described in the paper was the building of 

 Soulanges Canal, on the northern bank of the St. Lawrence, a 

 short distance above Montreal. Two very important departures 

 from ordinary practice were adopted on the advice of Mr. 

 Munro, who was sent on a tour through Europe by the Govern- 

 ment before the work was planned : in the first place, the locks 

 are practically all at the Montreal end of the canal, and the lift 

 in each lock was much greater than had previously been 

 attempted in Canada, the locks being also of great size ; in the 

 second place, Portland cement concrete has been extensively 

 used. Hitherto Canadian engineers have been afraid to use 

 this valuable material in their canal and harlx)ur work, mainly 

 on account of the fear that the severe Canadian winters would 

 break up such material ; partly also, at any rate, until a few 

 years ago, from the difficulty of obtaining trustworthy cement. 

 Recent advances in the manufacture, both in England and the 

 continent, stimulated mainly by the exhaustive series of tests 

 carried out on Portland cement by Bauschinger and others, 

 have resulted in putting at the disposal of Canadian engineers a 

 material thoroughly trustworthy and uniform in quality ; and 

 Mr. Munro's experience has proved decisively that with adequate 

 care in the preparation and use of the concrete it is perfectly 

 safe in the most rigorous Canadian winter. 



At Montreal the members of the section had the opportunity 

 of thoroughly inspecting the magnificent engineering laboratories 

 of the McGill University, built and equipped by Mr. McDonald, 

 one of the most generous in his gifts of the many public-spirited 

 citizens of that flourishing city. These la'boratories are in many 

 respects the most perfectly equipped in existence, especially the 

 hydraulic room designed by Prof. Bovey, where ihe visitors 

 were shown most ingenious appliances for studying some of the 

 more difficult problems in hydraulics, some of the appliances as, 



NO. 1456, VOL. 56] 



for example, the experimental steam pump, which has just been 

 installed, being on an extensive scale, and fitted for all the re- 

 quirements of complete research work. Prof. Bovey supple- 

 mented this visit by a paper read l>efore the section describing 

 in detail the various appliances in this hydraulic laljoratory. 



One of the most interesting discussions in the meeting of the 

 section was started by another paper of Prof Bovey, describing 

 the method of testing Canadian timbers at the McGill labora- 

 tories, and the results he had obtained as to the influence of 

 moisture on the strength and elasticity of the various woods 

 experimented on. The timber industry is such a valuable one, 

 both to Canada and the States, that special attention has been 

 devoted to the thorough testing of the economic values of the 

 different forest trees. It should be remembered, however, that 

 Bauschinger indicated the true method of making such tests in 

 his memoirs on testing of timber specimens : all the later ex- 

 perimenters have simply followed in his footsteps The results 

 of the exhaustive tests carried out in the States by Prof, Johnson 

 have been published in a series of Bulletins by the Forestry 

 Branch of the Department of Agriculture at Washington ; these 

 form a valuable series for reference. 



Prof. Callendar described in a brief, but most valuable paper, 

 which will be published in extenso in the transactions of the 

 British Association, the apparatus devised by himself and Prof. 

 Nicolson for studying the rate of condensation of steam when in 

 contact with metal surfaces at various temperatures and pressures. 

 The research is still incomplete, so that it is impossible to 

 deduce any very certain generalisation from the results so far 

 obtained with the apparatus ; but one thing has been clearly 

 brought out, namely, that the rate of condensation is not as great 

 as has hitherto been assumed in theoretical investigations into 

 this all-important question in the true theory of steam engine 

 efficiency. 



On the Saturday the members of the section had the oppor- 

 tunity of joining an excursion to Niagara, and of seeing while 

 there the various power-houses, and some of the industries 

 which make use of and depend for their existence on this cheap 

 and abundant power. Nothing has been more instructive to 

 English visitors than the constant utilisation of the energy of 

 the falls and rapids, so abundantly distributed all over Canada, 

 and nothing perhaps more striking than the fact that some of 

 these power companies find it difficult to dispose of the power 

 they are ready to supply, a testimony to the truth of the state- 

 ment that after all in many very important industries the cost of 

 power is not a very serious factor in the cost of production. 



As every city of any size, both in Canada and the States, is 

 always well equipped with electric tramcars or street railroads, 

 usually running many miles out into the country around, it was 

 only fitting that the section should devote a good deal of its 

 electrical day to papers on this question, so rapidly becoming 

 one of the leading problems of municipal engineering work in 

 Great Britain. 



Mr. Cunningham, the engineer responsible for the con.st ruc- 

 tion and working of the very complete system in use in Mon- 

 treal, read a paper descriptive of that work, but in doing so he 

 dealt fully with the whole question of electric as opposed to 

 other systems of traction. Here, again, many members had 

 had an opportunity of inspecting the power-houte of the 

 company at Montreal, and were able, therefore, to follow more 

 readily the author's description of the plant in use. 



Mr. Cunningham, no doubt, somewhat overstated his case 

 when contrasting the cost per car mile of the horse system of 

 Liverpool with the electric system of Montreal ; it is certainly 

 not a fair comparison to take the mere cost of power as delivered 

 from the power-house, neglecting all the expense of maintain- 

 ing the generating plant in prime cost condition, repairs to car 

 motors, lines, &c., and then to contrast this with the published 

 cost of haulage per car mile of some horse system, where not 

 only has the cost of fodder and wages of stablemen been in- 

 cluded, but also the heavy outlay of up-keep of the horse stock. 

 There can be no doubt that such comparisons have often led 

 municipal and other authorities in Great Britain to look with 

 great suspicion on estimates of electric street 1 ail way systems, 

 and have at times hindered their adoption. The distinct 

 economy of electric haulage, when every item of cost has been 

 fairly brought into the bill of charges, is so clear that it needs 

 no such unfair method of comparison to bring it home to those 

 interested in tramway work. 



There was a long discussion on this paper, and on a second 

 paper, by Mr. Aldridge, descriptive of a very ingenious but 



