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At first glance it may appear somewhat absurd to talk to Structural Engineers, or, indeed, any engineer, about welding or the high temperature treatment of modern industrial metals; most members of the engineering profession are more or less familiar with the theory and main principles governing the use of one or other of the half dozen fusive agents now universally employed by the specialist, but one finds quite commonly that an impression exists that welding has positive and well-defined limitations, or that its employment is only possible in certain classes of work and in relation to the union of certain metals. This prejudice is so widespread that it may be well at, the outset to assert without qualification that, in mechanical repairs and reconstructions and in the recreation of any of the industrial metals, there is practically no limit to its application. The idea, no doubt, had its origin in the unfortunate experience a certain number who have been the victims of incompetent operators, who have either failed to do what was required to be done or have employed an unsuitable process or fusive agent, with the inevitable result that the unit or member treated has lost efficiency or been irreparably damaged. C.W. Brett
In the Middle Ages, when mankind had considerably more leisure than at present for the consideration of what are now termed academic questions, one of the favourite subjects of discussion is said to have been, "Which came first; the hen or the egg?" No satisfactory conclusion appears ever to have been reached, and a busy world has since decided that the solution of the problem is one of the things that do not matter. We might ask nowadays, and with profit-the question being by no means as academical as it seems -who came first; the architect, or the engineer, civil, mechanical or structural? The first enterprising arboreal who bent a branch to serve as a foundation, or as a shelter for its tentative home; the first prehistoric man who adapted a cave to the purposes of a dwelling, was only imitating what the lower animals had done before: employing materials of the nature and properties of which instinct first, and a process of trial and error later, had afforded some rough empirical knowledge. He was thus certainly a structural engineer, one, that is, who employs materials for the purpose, first and foremost, of making a structure, even as the beaver, or the bird had done before him. Of purposive architectural design, or of knowledge of civil or mechanical engineering in all this there is little trace; the materials at hand were taken and adapted, according to their nature and suitability to a crude purpose. It seems almost indisputable, therefore, that a knowledge of the properties of materials, combined with eventual experience of their behaviour when built into a structure, must have been the primitive, and almost simultaneous bases of all knowledge of structures. These, and the selection of a suitable site and foundation; a tree, or a rock; a hummock, the open plain, or a treacherous and marshy tract necessitating, at the dictate of experience, the use of piles mask the early stages in the evolution of the structural engineer. His subsequent progress and development have been due to his increasing knowledge of materials and of their applications, but, more especially, of their limitations. To those with which nature originally endowed him he has added others. He has laid under contribution the discoveries of chemistry, and metallurgy, and has himself invented, and inspired the invention of the new materials suited to the new requirements he is called upon constantly to fulfil.
The Department of Scientific and Industrial Research has just issued, through H.M. Stationery Office, a volume of its special reports on the mineral resources of Great Britain. It deals with the geological relations, nature and uses, and mineral, chemical and physical properties of ball clays, that is to say, of those plastic "transported" clays which, when fired in an oxidising atmosphere to the temperature of certain pottery ovens approximately 1,150 deg.-1,200 deg. C.-have a white or nearly white colour. They are formed by the decomposition of felspathic rocks, by natural agencies. In this decomposition, silicates such as the felspars break down, and the products ultimately undergo hydration with the formation of the hydrated silicate of aluminium, kaolinite, and, in many cases, mixtures of hydrated oxides. Where these products are found resting in the parent rock, the clays are termed residual; where they have been transported and deposited elsewhere, they are known as transported clays. The china clays of Cornwall are typical examples of the former; the ball clays discussed in this memoir are characteristic examples of the latter. Dr. Alex Scott