The Mechanical Handling and Storing of Material

THE WAREHOUSING OF GRAIN 667 a Fresco in the Tomb at Beni-hasan. When new grain is brought into a granary it begins to sweat, and a rise of tem- ■ peiature is perceptible as well as a peculiar smell, which proves that not only does water escape but also a volatile oil. There must also be an escape of carbonic acid, for the heating of the grain can only be produced by the combustion of some of the solid substances, the starch being likely to suffer greater reduction than the small percentage of fat and protein. In order to keep the grain as nearly as possible at its right weight and in good condition it is necessary to prevent beating and only to promote evaporation of moisture artificially. This can be effected in various ways, the most common being to store the new grain in thin layers on the floor and turn it over frequently, until sufficiently conditioned to keep in silos. The method of turning wheat over in silos is less effectual, especially in the case of very new wheat, than-the former method. When wheat is thus stored in thin layers the grains absorb oxygen constantly and issue carbonic acid in exchange for the oxygen taken up; they are in fact in a state of slow combustion. The hygroscopic nature of the grain is responsible for this action, as the grain absorbs moisture in a damp atmosphere and gives off moisture in a dry atmosphere. According to Muntz, the more the air is renewed the moister the grain, and the higher the temperature the greater is the issue of carbonic acid. It follows then, from the above, that in order to store conditioned grain to the best advantage it should be kept in a dry and cool place, and the air excluded as much as possible. Some experiments as to the keeping quality of grain were made by Mr Doyére,1 who in 1820 constructed a silo in which grain was kept for eight years. When the French Government ordered an investigation of the subject in 1855, Mr Doyére reported that the system of storing grain in silos greatly retarded decay, and that corn containing 21 per cent, of moisture and in contact with the air gave off 17 mg. of carbonic acid per kilogram per hour, or 408 mg. per day, while with the air excluded and at an average temperature of 68° F., the carbonic acid given off per day was only 120 mg. From this it would appear that grain exposed to air decomposes three and a half times as fast as when stored in enclosed silos. The experiments of Professor Tyndall2 and of the late Mr Pasteur also bear out this conclusion. The above, of course, refers only to the storage of grain in good and sound condition. New and damp grain containing a large percentage of moisture would not be safe from decomposition even if stored in perfectly air-tight silos. Such grain must be dried or conditioned artificially, stored in shallow bins, and turned over frequently until it is in a suitable condition for keeping.3 The origin of grain warehouses is attributed to Hungary, but these early examples 1 “Conservation des Grains par 1’Ensilage,” by L. Doyére, Paris, 1862; and “Silos, Ensilage, and Silage,” by Dr Manby Miles, New York, 1889. 2 “ Essays on the Floating Matter of the Air,” Second Edition/London, 1883. 3 Proceedings Inst. Civil Engineers, vol. cxxvi., Paper No. 2815, by P. W. Britton, on the “ Transport and Storage of Grain.”