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SIR,-The paper reported in the April issue on La Roche Guyon Bridge, which was presented at a joint meeting of the Institution of Structural Engineers and the British Section of the Societe des Inghieurs Clivils de France, appears to be in the nature of further propaganda on the use of long span bridges in ferroconcrete. At a similar joint meeting some time ago, this subject was dealt with in a more general way. At both meetings the authors of the papers were advocating the use of reinforced concrete in preference to steel for long span bridges. Statements have been made that reinforced concrete is more economical than steel for spans of well over 1,000 ft. It is difficult to believe that such extravagant claims would bear impartial investigation. They are apparently arrived at by using very high stresses in the concrete-in fact far greater than have ever been dreamed of in this country. It would therefore seem that the comparison is made by using high stresses in the concrete and normal stresses in the steel. If a concrete structure can be over-stressed with safety, surely it would seem still safer to over-stress a steel one by a proportionate amount, in which case the comparative economic span lengths would be very different from those claimed.
THE use of arc welding in multiple storey steel frame buildings is quite a recent development, but already sufficient structures have been erected to enable the nature of the problem to be appreciated and the probable future progress to be estimated. It is certain that when efficient workshop methods are adopted and proficiency in erection acquired, welding will gradually become the normal method of construction. A. Ramsay Moon
DR. OSCAR FABER, O.B.E., whose name is so well known in the sphere of structural engineering and whom we welcome as our new President, first joined the Institution (then the Concrete Institute) in 1911.