TKANSACTIOXS OF SECTION G. 873 



ample in amount without extravagance, and easily laid witliout the responsibility 

 of supervision in placing the material transversely at the specified distances apart, 

 as would be necessary in the case of separate pieces. The insertion of Avires or 

 individual sections gives strength in the direction of their length, leaving the inter- 

 mediate concrete comparatively weak. Expanded metal contributes strength 

 laterally both in the direction of width and length, as well as giving an effective 

 keyage in its depth. The coefficients of expansion of the two constituents, iron or 

 steel and concrete, are considered for all practical purposes to be identical. Results 

 of experiments made on various-size slabs were next given, the longest span without 

 intermediate joists being on a slab 12 ft. 6 in. by II ft. clear span, which was loaded 

 to 6j cwt. to the foot super, and bore this load for H hour before it collapsed, the 

 fractures occurring at each of the four corners. The gradual increase of the load 

 and progress of deflection of the slab were related in detail. 



The adhesion of iron and concrete was found by Professor Bauschinger, of 

 Munich, to be about 569 to 668 pounds per square inch, but a case was quoted, 

 experimenting upon 2 in. diameter anchor bolts set 11^ in. in a masonry block, with 

 lead, sulphur, and cement, from which it was inferred that in suitable setting the 

 cement joint on a smooth rod might be made to fracture the rod before the adhesion 

 of the connection failed. The author described the introduction of the aid of 

 channel arches by the Expanded Metal Company. The spans were enabled to be 

 increased thereby, the only objection being, in the author's opinion, the exposure 

 of the under surface of the channel metal rib ; but the surface so exposed is com- 

 paratively small compared with the various systems of trough flooring that have 

 been patented. The result of experiments was stated in the paper, the channel 

 metal flat arches being firmly held between lougitudinal joists spaced at specified 

 intervals. The author considered that, in order to keep the portion of a slab 

 containing metal in tension below the neutral axis, the slab should not be fixed at its 

 bearings ; but he pointed out that probably there is a tendency to form a fiat arch 

 Avithin a concrete beam, which converts a large part of the vertical pressure into 

 lateral thrust, which in the case of an expanded metal section becomes a tied arch, 

 and that, in his opinion, a concrete beam should be viewed as a bar. with a hollow 

 curved soffit. Further developments of the system were reviewed, and diagrams 

 illustrative of the arguments propounded were exhibited, with a view to elicit 

 suggestions as to any desired improvement in the size of the meshes employed or 

 to further experiments needed. 



6. Power Generation.— Comparative Cost by the Steam Engine, Water 

 Turbine, and Gas Engine. By John B. C. Kershaw, F.I.C. 



There is no question of greater importance at the present moment to those 

 engaged in the management of our manufacturing industries than that of power 

 generation. The supremacy which the steam engine has so long enjoyed is now 

 assailed from two sides. The water turbine and the gas engine have become 

 dangerous rivals. 



During the past ten years a most remarkable development of hydraulic power 

 has been taking place on the continent of Europe in France and Germany, and in 

 America at Niagara. 



The aggregate amount of power at the present date generated from falling 

 water forms no inconsiderable portion of the total power utilised in manufacturing 

 industries ; and two years ago it was estimated by the author to be between 

 236,000 and 350,000 horse-power. 



On the other hand gas engineers have been busily engaged in working out the 

 problems presented by large gas engines and by the utilisation of the waste gases 

 of blast furnaces. 



Gas engines up to 650 horse-power have been built, and have worked smoothly 

 and economically ; while at Seraing in Belgium and at other places the blast 

 furnace gases have been utilised for driving the engines which supply the blast. 



The question, therefore, which the engineer now has to settle when deciding 

 upon the site and locality for a new factory, or when deciding upon the system of 



