The Mechanical Handling and Storing of Material

668 THE MECHANICAL HANDLING OF MATERIAL were comparatively small structures, and do not appear to have been provided with any noteworthy appliances for the mechanical handling of grain. It is to America that the credit belongs of designing granaries capable of holding immense quantities of grain and seeds, and of equipping these warehouses with machinery to obviate as far as possible the necessity of employing hand labour in the handling of the grain. In these warehouses (known in America as “ Elevators ”) air is excluded as far as possible, but in all modern granaries there is this important departure from the original method, that the grain is stored, not in the earth, but in silo bins or some other structure above ground. Silo warehouses1 2 have been known in America since 1846, when they first came into general use, and large installations have since then been erected at all the most important grain producing centres, as well as at the points where grain is exported. It was not, however, until the beginning of 1880 that the first silo warehouse of any great capacity was built in New York. One of the most valuable features of the American silo system is this, that it enables the agriculturist to store his grain cheaply under the best con- ditions, and to hold it until the market is favourable to a sale. He can also mortgage his grain while he is waiting for a fair price. In America this system has been carried out on an enormous scale. A holder can store his grain in a granary, say at Chicago, and can withdraw grain of a similar grade from some other warehouse, say at New York. In fact the grain trade there is carried on somewhat after the manner of the clearing house in the money market. Comparing the floor system with the silo system for the storing of grain, it may be mentioned that where silos are applicable the same capital outlay will provide a granary of the latter type which will accommodate twice as much wheat as one on the floor system. Silos, their Shape and their Construction.—Silos may be either square, circular, or hexagonal, and may be built of wood, brick, concrete, iron, or a combination of the two latter—reinforced concrete. The choice of material depends to some extent upon climatic conditions. The most suitable material for square bins is wood, for circular bins iron, and for hexagonal bins brickwork or concrete. Circular silos are the strongest, but are less economic in space than the other two forms. A large number of circular iron silos are used in America, the space between four large bins frequently being occupied by a smaller one. Wood,- as a material for building silos, has the advantage of being light, strong, inexpensive, a non-conductor of heat, and hygroscopic. It has also the further advantage of yielding to an unequal pressure or to a possible settlement of the structure. One of the most usual forms of construction is perhaps that known as the early American system, or “cribwork,” which consists of flat strips of wood nailed one on top of the other, and overlapping each other at the corners, so that alternately a longitudinal and a transverse batten extend past the corners. Short pieces of timber are nailed down on the spaces forming alternate gaps, so that the whole silo wall is solid to the end. This is undoubtedly a strong form of bin, but it has certain disadvantages. The planks are liable to dry-rot and cannot be renewed except with great difficulty. Bricks or cement are suitable materials for the construction of silos, as they are bad heat conductors; they are, however, lacking in hygroscopic properties. The drawbacks 1 To avoid misunderstanding, the term “elevator” (which is in America largely applied to these warehouses) has not been adopted in this book, as in this country the word is exclusively used with reference to ordinary elevating machinery and not to granary buildings. 2 Paper by Mr P. W. Britton on the “ Transport and Storage of Grain,” also paper by Mr J. Whitaker, A.M.Inst.C.E., on “Silo Granaries for Modern Flour Mills.”