on a single block of the same construction. The cost of these foundations was less than the estimate made for the same in first-class brick or stone mason-work.
It has also been used for lining a reservoir of ninety-six thousand gallons capacity, which was blasted into a ledge.
Another great advantage realized in re-enforcing béton with iron, is that the iron overcomes its tendency to check in hardening, within useful limits, however large the surface may be, if the distribution of the iron through the work is made with ordinary good judgment. This is demonstrated in the instance of entire freedom from shrinkage checks in the single section of béton-flooring laid in the drawing-room of the house. Its dimensions are eighteen by thirty-six feet, three and a half inches thick, and after a period of eight years, during six of which it has, in winter, been more or less subjected to unequal strains from the expansion and contraction, caused by changing temperatures, while employed as a transmitting medium of heat for warming the room, there is no trace of a check throughout its whole extent.
The method of heating the house is shown in Fig. 2, where the section exhibits the arrangement of hot-room and heating-flues in the walls and floors.
In the center of the cellar is a heating-chamber, measuring eleven by sixteen feet, and eight feet in height. Within this chamber is placed an ordinary cast-iron heater, of a capacity for burning about three hundred and fifty pounds of coal per day. Openings were made, about twelve inches apart, all around the top of the surrounding walls of the chamber, leading outwardly to the spaces between the first floors and the cellar-ceilings, and also up through the flues within the interior walls, which communicate with the spaces between the second story floors and ceilings beneath them. Vertical iron pipes, of suitable size, are located so as to connect the open spaces between the cellar-ceilings and first floor with a large, closed trunk, or passageway, which extends nearly all around the inside of the main wall foundation, under the cellar-floor, and finally terminates in a large flue, which leads directly under and into the heating-chamber.
This comprises about the whole system of arrangements in the construction for warming the house with heat radiated from the floors and interior walls.
Its mode of operation simply consists in the body of warmed air passing from the heating-chamber upward, through the walls and under the floors, and in its passage giving up its surplus heat to the surfaces of these flues. As the air becomes reduced in temperature, it naturally descends through the pipe and trunk passage-ways provided for its return to the heating-chamber, where it is again recharged with heat. It will readily be seen that, by this method, a continuous circulation will be maintained with the same quantity of air; and furthermore, that the velocity of the current will vary with the dif-
