"The earthen walls are four feet thick at the floor of the kiln, seven feet high, and tapering to a thickness of two feet at the top; this will determine the slope of the exterior face of the kiln. The inside of the wall is carried up perpendicularly, and the loam plastering inside becomes, after the first burning, like a brick wall. The kiln may be safely erected in March, or whenever the danger of injury from frost is over. After the summer use of it, it must be protected, by faggots or litter, against the wet and frost of winter. A kiln of these dimensions will contain 32,500 1-1/4-inch tiles, * * * or 12,000 2-1/4-inch tiles. * * * "In good weather, this kiln can be filled, burnt, and discharged once in every fortnight, and fifteen kilns may be obtained in a good season, producing 487,500 1-1/4-inch tiles, and in proportion for the other sizes. "It requires 2 tons 5 cwt. of good coals to burn the above kiln, full of tiles." [Fig. 46 - CLAY-KILN.] Fig. 46 - CLAY-KILN. A sectional view of this kiln is shown in Fig. 46, in which _C, C_ represent sections of the outer trench; _A_, one of the three fire-holes; and _B, B_, sections of a circular passage inside of the wall, connected with the fire-holes, and serving as a flue for the flames, which, at suitable intervals, pass through openings into the floor of the kiln. The whole structure should be covered with a roof of rough boards, placed high enough to be out of the reach of the fire. A door in the side of the kiln serves for putting in and removing the tiles, and is built up, temporarily, with bricks or clay, during the burning. Mr. Hodges estimates the cost of this kiln, all complete, at less than $25. Concerning its value, he wrote another letter in 1848, from which the following is extracted: "The experience of four years that have elapsed since my letter to the late Earl Spencer, published in the 5th volume of the proceedings of the Royal Agricultural Society, page 57, has thoroughly tested the merits of the temporary clay-kilns for the burning of draining-pipes described in that letter. "I am well aware that there were persons, even among those who came to see it, who pronounced at once upon the construction and duration of the kiln as unworthy of attention. How far their expectations have been realized, and what value belongs to their judgment, the following short statement will exhibit: "The kiln, in question, was constructed, in 1844, at a cost of £5. "It was used four times in that year, burning each time between 18,000 and 19,000 draining pipes, of 1-3/4 inches in diameter. "In 1845, it was used nine times, or about once a fortnight, burning each time the same quantity of nearly 19,000 pipes. "In 1846, the same result.