To carry a slate roof 30 It. wide, with a clear headway of 16 ft. and with a span of 50 ft., there will be required four cast-iron E stanchions about 8 in. by 6 in. by 3/4 in., with nroper cap and base and good foundations. Two steel lattice girders in fifteen bays, with a depth of 3 ft. 6 in., and each capable of carrying with safety 20 tons distributed, and six king- or queen-post trusses if of wood, or of trussed rafter design if of iron, with the usual purlins, etc., will also be necessary.

Girders and Columns for Carrying Roof.