SIR,-The papers by Dr. Cassie on "Bond Resistance of High Strength and Vibrated Concrete," and Dr. Evans on "Stresses in the Steel Reinforcement of Reinforced Structures," may properly be discussed together, as they both deal with the allied phenomena of adhesion and creep. Elsewhere I have tried to show that these phenomena depend on the fundamental properties of colloid gels, of which hydrated Portland cement-in its early stages-is an example; that creep is due to the expulsion of colloid water, which has since been largely confirmed by Davis's experiments; and that bond is due to adhesion-not friction-and bond resistance depends on the initial shrinkage in the concrete. The following remarks spring largely from these theses; and it is hoped that they may give rise to some of that acute disagreement which generally leads to an interesting discussion.
Mr. MACBRIDE, having presented the paper, exhibited a cinematograph film showing some of the details of the welded joints and of the structure generally, and the actual process of welding. He commented upon the extreme simplicity of the floor beams, and upon the fact that the connections were welded very quickly.
Mr. C. J. JACKAMAN, A.M.Inst.C.E. (Member of Council), proposed a hearty vote of thanks to Mr. Turner for his very instructive and interesting paper. Mr. Jackaman confessed that he was almost envious of Mr. Turner’s experience, which must be unique in its character, because he had been dealing with very heavy structures built on strata such as we could not visualise in this country; and he was to be congratulated most heartily on the success which had attended his efforts.
BRIDGES. A REMARKABLE feature of post-war engineering in this country has been theimprovement of the road system and one of the most urgent needs in road improvement is the replacement, or widening and strengthening, of old-fashioned or inadequate bridges. The worst of these are frequently found across canals. As Canal companies are under no obligation to improve them, this work must be carried out by Municipal or Precepting Authorities. In Coventry, Red Lane Bridge over the Coventry Canal is now in course of replacement and the replacement of Tusses Bridge over the Oxford Canal will shortly be commenced. A.L. Percy
Has it occurred to you that some one or other of the professional advisory bodies of the building industry might act as a clearing house for codes, etc., affecting structural work and that it would be well if all building organisations interested were to make up their minds as to which body they would use for this purpose and stand by their decision.
In spite of the great activity in bridge building which has continued in this country, as in others, since the war, it is still true to say that most bridges now existing were originally built for loads much below those they now have to bear. Many are adequate owing either to extraneous aids, such as the consolidation and cohesion of filling round them, or to their original factor of safety having been high enough to cover the effects of modern loading; but more, perhaps, need either strengthening or complete reconstruction. C.S. Chettoe