In country districts the roofs of cottages and outbuildings are frequently covered with thatch. This consists of layers of straw--wheaten lasts twice as long as oaten--about 15 in. in thickness, tied down to laths with withes of straw or with string. Thatch is an excellent non-conductor of heat, and consequently buildings thus roofed are both cooler in summer and warmer in winter than others, and no better roof covering for a dairy can be found. Thatch is, however, highly combustible, and as it harbours vermin and is soon damaged, it is not really an economical material, though the first cost is small. A load of straw will do 1½ “squares” of roofing, or 150 superficial feet. First class thatching is an art not readily acquired. While really good thatching will stand for 20 years, average work will not endure 10. A convenient roofing material when wood is cheap and abundant consists of a kind of “wooden slates,” split pieces of wood measuring about 9 in. long, 5 in. wide, and 1 in. thick at one end but tapering to a sharp edge at the other. Shingles, or wooden slates, are made from hard wood, either of oak, larch, or cedar, or any material that will split easily. Their dimensions are usually 6 in. wide by 12 or 18 in. long, and about ¼ in. thick. Roofing felt is a substance composed largely of hair saturated with an asphalte composition, and should be chosen more for closeness of texture than excessive thickness. It is sold in rolls 2 ft. 8 in. wide and 25 yd. long, thus containing 200 ft. super in a roll. Before the felt is laid on the boards (¾ in. close boarding), a coating composed of 5 lb. ground whiting and 1 gal. coal tar, boiled to expel the water, is applied, while still slightly warm, on the boards themselves; the felt is then laid on, taking care to stretch it smooth and tight, and the outside edge is nailed closely with ⅞ in. zinc or tinned tacks. The most common application to a felt roof is simple coal tar brushed on hot and sprinkled with sharp sand. It is not well adapted to dwellings. Dachpappe is a kind of asphalte pasteboard much employed in Denmark; it is laid on close boarding at a very low pitch, and forms a light, durable covering, having the non-conducting properties of thatch. It is sold in rolls 2 ft. 9 in. wide and 25 ft. long, having a superficial content of 7½ sq. yd., at the rate of 1_d._ per sq. ft. When laid, it requires dressing with an asphalte composition called “Erichsen’s mastic,” sold at 9_s._ 9_d._ per cwt., 1 cwt. of the varnish sufficing to cover a surface of 65 sq. yd.