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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.