June 29, 1905] 



NA rURE 



even if it were not more economical tlian the best steam- 

 driven machines, was certainly not more expensive. The 

 greater facility and safety with which electricity can be 

 used, the smoothness with which it works, and its much 

 greater flexibility, would often make it preferable to the 

 use of steam, even in a case where transmission of energy 

 was not required ; there could be no hesitation in the 

 choice between the two systems when the power had to be 

 transmitted from a distance, or where the production of 

 energy could be centralised at one power station. 



iM. Ed. Noaillon's paper on ferro-concrete was next 

 read. Ferro-concrete constructions, as is well known, 

 consist of a mass in which iron or steel reinforcement is 

 bedded. The author stated that round bars were generally 

 used, as they facilitated the escape of air and the proper 

 ramming of the concrete ; there were also no sharp angles 

 which would cut the concrete. On the other hand, the 

 round section gave the lowest coefficient of adhesion for a 

 given cross-section of metal. The following rules govern- 

 ing the construction had been prepared by Prof. Rabut : — 

 (i) No connection should be made of iron to iron, as the 

 concrete itself holds the parts together in the most 

 economical manner. (2) At least two distinct systems of 

 reinforcement should be used, one to take up the tensile 

 stress and the other to take up the shearing stresses in 

 the concrete ; when necessary a third system should be used 

 to take up the compressive stresses. (3) The reinforcement 

 should be so arranged that the separate members may be 

 stressed in the direction of their length, so that the stresses 

 produced between the iron and the concrete should be 

 tangential, and not normal to the axis of the members 

 of the reinforcement. (4) Homogeneity of the structure 

 should be taken advantage of \>\ prolonging the iron parts 

 of one portion of the structure into the thickness of the 

 concrete of the adjoining portion. Other points were also 

 given. 



Methods of construction were described and illustrated. 

 Some examples of reinforced concrete were given in the 

 paper, the handsome dome of the new Central Railway 

 Station at .Antwerp being a prominent instance. This 

 dome is a fine piece of architecture, but was designed first 

 of all for an ordinary masonry structure, a fact which 

 made it somewhat difficult for the architects to ad.ipt it for 

 ferro-concrete. The entire structure is 1800 tons in w^eight, 

 and rests wholly upon the columns at the angles of the 

 glass lights : these columns are Y-shaped in cross-section. 

 The external shell has a uniform thickness of 3-15 inches, 

 and is relieved by six moulded ribs following the meridian 

 lines. The Renomm^e Hall at I^i^ge was the next example 

 of this kind of construction. It was designed expressly 

 for the use of this material. The principal hall is covered 

 by three cupolas, each 55 feet in diameter, placed at a 

 height of about 50 feet above the level of the ground. 

 Each cupola forms part of a sphere, which continues in 

 haunches, pierced with lights, and descending to the corners 

 of the circumscribed square. The intersections of the 

 spheres with the vertical spans passing through the sides 

 of the squares are formed by arched beams, which spring 

 from the capitals of short cylindrical columns. The 

 cupolas are 45 inches thick, and are made of concrete com- 

 posed of cement clinker finely broken up ; they are re- 

 inforced by a layer of expanded metal with a lattice work 

 of bars. Members of the institution had a good oppor- 

 tunity to examine this structure, as one of the banquets 

 during the meeting was given in the Renomm^e Hall. 



An interesting application of reinforced concrete was 

 also described in the widening of La Boverie Bridge 

 at Li^ge. Particulars were also given of another bridge, 

 built upon the Hennebique system ; the length between 

 abutments was 260 feet, and comprised a central span of 

 I So feet and two side spans. The total width of the road- 

 way was 328 feet. .\n interesting feature about this bridge 

 is the design of the foundations, and the way they were 

 erected by mechanical compression of the soil. The piers 

 and. abutments rested upon a group of concrete piles driven 

 deeply into the bed of the gravel, which thus became 

 strongly compressed. The concrete piles were reinforced 

 by vertical bars of steel which were continued into the 

 piers and abutments, so that the whole w-as solidly bound 

 together. By this method the advantage was obtained 

 of solidly rooting the bridge into the earth, so that it 



had a resistance amply suflicient in case of a floating 

 accumulation of ice, such as would temporarily transform 

 the bridge into a dam. A skew bridge, also on the 

 Hennebique system, was referred to, and a description was 

 also given of a framework for lead chambers at the 

 chemical works of the Engis Co. In the brief discussion 

 which followed this paper, Mr. W. H. Maw suggested 

 that it would be interesting if experiments could be made 

 upon the effect of tension upon bars held in concrete. He 

 had heard that a better hold of the concrete was obtained 

 if the bars were previously treated to a wash of cement. 



Mr. Mellanby's paper on the efficiency of the steam 

 jacket was next read. This paper may be said to form 

 part of a series of contributions on the same subject which 

 have been given by various authorities during recent times. 

 The results of a series of somewhat elaborate trials were 

 given, from which the following general results may be 

 taken. A compound engine, with boiler pressure at 150 lb., 

 may be worked with the mean pressure referred to the 

 low-pressure cylinder of about 40 lb. per square inch with- 

 out any loss of efficiency in terms of the brake horse- 

 power. Steam jackets have their maximum efficiency when 

 the whole of the high-pressure and the ends of the low- 

 pressure cylinders are jacketed with high-pressure steam. 

 When jackets are applied to the high-pressure cylinder, 

 the total indicated horse-power is slightly reduced, but 

 when applied to the low-pressure cylinder the total in- 

 dicated horse-power is considerably increased. Jackets have 

 little effect in the high-pressure, but have considerable 

 effect in the low-pressure cylinder upon initial condensa- 

 tion. The temperature supplied to the cylinder walls next 

 to the steam must be considerably less than thatof the 

 steam, because, firstly, the actual " missing quantity " is 

 much less than it would have been had the steam and 

 metal gone through the same temperature changes, and 

 secondly, because the mean temperature of the metal is 

 higher than that of the steain. The author concluded that 

 the greater part of the " missing quantity " must be due 

 to leakage, and not to initial condensation, in this respect 

 agreeing with the conclusions of Messrs. Callendar and 

 Nicolson. 



A somewhat extended discussion followed the reading of 

 this paper. It was opened by Mr. V. Pendred, who said 

 that compression in the cylinder had a considerable effect. 

 If the compression corner of the indicator diagram was 

 square, the utility of the jacket appeared to be small, but 

 if it were rounded off by compression jacketing appeared 

 to be more effective. Mr. Saxon, of Manchester, took 

 exception to the statement as to a mean effective pressure 

 of 40 lb. being the most eflficient for a compound engine; 

 he considered that the ratio of the cylinders should be 

 taken into account. Mr. Henry Davey did not regard 

 the results obtained as a guide for engineers, on account 

 of the bad performance of the engine. Mr. Mark Robinson 

 confirmed the author's opinion in regard to a mean pressure 

 of 40 lb., and, in reply to a remark of Mr. Saxon's, said 

 that the sire of the cylinders should be in accordance with 

 the power needed, and their ratio should be governed 

 by the conditions of working. 



On the second day of the meeting the first paper taken 

 was a contribution by Mr. R. Mathot on large gas-engines. 

 This was a long and interesting paper, containing a con- 

 siderable amount of historical matter, and dealing with 

 many of the details of construction by Continental makers 

 in the design of large gas-engines, which have formed so 

 prominent a feature of the engineering of Germany and 

 Belgium within the last few years. The paper was illus- 

 trated by a number of engravings and diagrams, and 

 results of engine tests were given in a table. Although 

 English engineers early took the lead in the manufacture 

 of "gas-engines of moderate size, they have been to some 

 extent left behind by Belgian and German manufacturers 

 in regard to large gas-engines using blast-furnace gas : 

 and even such of the latter as have been constructed 

 in England have been mostly to German designs. It would 

 be impossible in a report of this nature to give an account 

 of the many details of construction dealt with by the 

 author, especially without the aid of the numerous illus- 

 trations by which the paper was accompanied. 



The discussion that followed the reading of the paper 

 tnainlv consisted of a speech by Mr. Crossley, of Man- 



NO. 1861, VOL. 72] 



