S04 Scientific hitelligence. — Arts. 



covering public buildings, private dwellings, and warehouses. 

 The expence of this cast-iron roof, compared with one of lead, 

 including deductions for the want of close boarding, which is 

 indispensable for a lead covering, is quoted at not more than 

 one-third of the expence of a leaden roof. At the Toll-end fur- 

 naces in Staffordshire, the expence of these cast-iron plates is 

 stated atL. 11, 10s. per ton, and the freight to London at L. 1, 

 10s., and about one-third less to Bristol, Liverpool, and Hull. 

 It is also said, that, owing to these plates being small, and loose- 

 ly fitted together, they are less subject to fracture from changes 

 of temperature than lead, which is frequently confined, and does 

 not allow room for the contraction and expansion occasioned by 

 changes of temperature. A slate roof is estimated by the pa- 

 tentee to last about fifty years ; while, in that time, the iron 

 would scarcely be deteriorated ; and in case, he adds, of destruc- 

 tion of a building by fire, the old iron will be worth nearly half 

 of its original cost. A square of 100 feet of these plates is es- 

 timated to weigh 1000 lb., while the same one of copper roofing 

 weighs, according to Tredgold, 100 lb. of lead, 800 lb. of large 

 slates, 1120 lb. of ordinary slates, 900 lb. to 500 lb., and of 

 pan tiles 1780 lb. to 650 lb. It is particularly suited, in point of 

 taste, to the Grecian style of architecture, inasmuch as it re- 

 quires to be laid at a less angle than is common with any other 

 metallic covering. The effect also produced by the simple and 

 regular form of the parts composing this covering, is said to be 

 pleasing ; and the eye is relieved by the lights and shades which 

 arise from the alternate projection, the apparent thickness, and 

 from the gradation of the plates. The patentee recommends 

 that the plates be three-sixteenths of an inch in thickness, and that 

 they be cast in squares of two feet, with flanges of two inches in 

 depth. The weight of these plates will be about 10 lb. per 

 square foot ; and he conceives that this roof will require no fas- 

 tening, but that their weight and particular construction will se- 

 cure them against the effects of high winds. But should any 

 one be doubtful of this, he proposes to cast a loop in the under 

 side of each plate of the raised row of plates, by which they 

 may be hooked or chained down to the rafters. It must be ob- 

 vious that the raised rows would effectually secure the sunk 

 ones in their places. This contrivance we consider as ingenious. 



