Canadian engineer . on will, however, make clearthe consitruction, the method of which is the following :—Onthe surface of the pyramid formed in the ground a fewinches of plain concrete are deposited, and this forms thematrix for the cone of reinforced concrete. The cone is cir-cular in plan, so that the thin covering of concrete has theform of an inverted saucer. As an example of one of these cone foundations actuallycompleted, one may be selected having on it the exception-ally heavy load of 612 tons in a newly-built boiler-house inFrance. The allowable pressure on the soil was 5,000
Canadian engineer . on will, however, make clearthe consitruction, the method of which is the following :—Onthe surface of the pyramid formed in the ground a fewinches of plain concrete are deposited, and this forms thematrix for the cone of reinforced concrete. The cone is cir-cular in plan, so that the thin covering of concrete has theform of an inverted saucer. As an example of one of these cone foundations actuallycompleted, one may be selected having on it the exception-ally heavy load of 612 tons in a newly-built boiler-house inFrance. The allowable pressure on the soil was 5,000 sq. ft., so that the required base area of the cone was275 sq. ft., and the diameter 18 ft. 8 in. The angle of thegeneratrix of the underside of the cone with the horizontalwas 30 deg. It is hardly necessary to say that great care has to beexercised in designing these cones, for the vertical load fromthe column produces not only a bursting pressure on thecone, which varies in intensity from the apex to the circum-. Sketch Showing Arrangement of Foundation in Place. ference, and which has to be carried by a proper number ofcircular rings pitched at varying distances, -but, in additionto the primary bursting effect, there is a coonpression vary-ing also in intensity from the apex downwards, to withstandwhich the concrete must be of sufficient thickness at eachpoint. Adequate concrete and steel must also be providedt3 prevent the column from perforating the top of the coneby shearing it through vertically. These considerations,however, do not affect the practical construction, which issimple, no temporary shuttering being required. It is understood that although the method has been in-vented and perfected by M. Considere for only a short time,a number of important buildings have already been erectedon these foundations, among them being a new dock ware-house at Havre, where the column loads are 195 tons; aboiler-house near Paris, with column loads of 612 tons; anda warehouse at
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