The Erection of Heavy Drums

DURING the last few years the term "Stadia" has frequently been used in describing sports enclosures. It is derived from the old Greek word " Stadium," which originally applied to the foot race course at Olympia. This structure was erected in the 3rd century, B.C., and was 630 feet in length, with two parallel tiers of stone seats along each side, joined at one end by a semicircular curve. It is interesting to note that the distance between the two end pylons measured 606.75 feet, and that this was afterwards adopted by the Romans as a measure of distance, eight "Stadia" being equal to one Roman Mile. James Reed

It is no exaggeration to say that the success of reinforced concrete as a structural material has depended very largely on the ability of concrete to adjust itself to stress conditions by means of creep. Scattered through the literature of reinforced concrete we find reference to this power of self -adjustment from the very early days of reinforced concrete construction, but it is only comparatively recently that the mechanism by which it operates has been investigated sufficiently to enable us to predict the progressive stress changes with some semblance of accuracy. It may well be suggested that this investigation, involving as it does all the factors producing progressive volume and length changes in concrete, has done more to extend our knowledge of the behaviour of reinforced concrete than anything else during the last decade. As a consequence, those who have studied these changes have learned to regard the assumptions we have to make in order to produce designs within a reasonable period from a new angle, and to realise that, although they serve reasonably well as a means to an end, they result in computed stresses that are, in general, very different from the actual stresses. W.H. Glanville

SIR,-. Kent’s comments relating to my communication on “Dynamic Effects in Railway Bridges," published in the November number of The Structural Engineer, are very much to the point, but I think he is perhaps unduly pessimistic. There is no getting away from the fact that the state of oscillation in a bridge, when synchronism is encountered, is governed to a large extent by those somewhat elusive characteristics, damping in the bridge and damping in the spring movement of the locomotive; but it should not be impossible to assign numerical values to the coefficients prescribing those characteristics with a degree of accuracy sufficient for all practical purposes.