18G9.] Concrete and Teton. G97 A COUNTRY CHURCH IN CONCRETE. ness in their very form. We allude to the hole in the heart, which is meant for purposes of ventilation, but is fatal to the' first principles of strength. The proportion of lime to that of sand is not sufficient for the perfect cementation of the mass, and we do not believe that any amount of pressure can prove suf- ficient to make up the deficiency and produce the requisite cohesion. But, the failure of these very noat looking " blocks " is no argument what- ever against concrete as a constructive material above ground. It is simply a proof of the absurdity of endeavoring to over-refine a mere principle, and to make a theory carry more than is prac- tically safe. Concrete, to be enduring and capable of bearing superincumbent pressure, must, as we have already said, be com- posed, in three distinct parts, of broken stone ; coarse, sharp or siliceous sand ; and good, lively quick-lime. The pro- portions of these three materials are so calculated as to leave no void in the mass and to bring all perfectly together. We will now proceed to specify the neces- sary operations, and to that end pre- sent the above illustration of a country church executed in concrete. The trenches of the foundation being filled to the surface of the site, the whole will be levelled off all around, and four moulds, previously prepared, placed one on each wall. These moulds will be formed in the fol'owing manner : Take well seasoned pine-boards an inch and a quarter thick, and cut them into lengths of three feet ; clamp them 1 strongly, with say three stout clamps. Groove them on the inside within three inches of the extremities, and fit into these grooves two ends, an inch and a quarter thick. In order to secure the whole, rods of iron, of about a quarter of an inch in diameter, will be run through from side to side, above and below, out-
