PROFESSOR ALEXANDER GRAHAM BELL _Frontispiece_ BELL HOMESTEAD, BRANTFORD, ONTARIO _facing_ 2 Lens of ice focussing a sunbeam 5 Rubber strip suspended plank-wise and joist-wise 7 Board doubled breadthwise and edgewise 7 Telegraph poles under compression. Wires under tension 8 Rubber cylinder, flattened by compression, lengthened by tension 9 Rubber joist compressed along top, extended along bottom 10 Girder cut from joist 10 Rubber I-beam suspended flatwise and edgewise 10 Girder contours simple, built up, in locomotive draw-bars 11 Steel ore car 12 Bulb angle column, New York Subway 12 Strap rail and stringer, Mohawk & Hudson R. R., 1830 13 PLIMMON H. DUDLEY _facing_ 14 Dudley rails 16 Steel cross-ties and rails 17 King-post truss 18 Frames of four sides 19 Cross-section Arctic ship “Roosevelt” 20 Pair of compasses stretch a rubber strip 20 Queen-post truss 21 Upper part of roof truss, Interborough Power House, New York 21 Two queen-post trusses from a bridge 22 Palladio trusses 22 Burr Bridge, Waterford, N. Y. 23 Howe and Pratt trusses 24 Baltimore truss 25 Whipple Bridge 25 Simple cantilevers 26 Victoria Bridge, Montreal, original form 27 Victoria Bridge, Montreal, present form 28 Cantilever Bridge, near Quebec 29 Kentucky River Cantilever Bridge 30 Arch Bridge, Niagara Falls 31 Bowstring Bridge, Philadelphia 32 Williamsburg Bridge, New York City 33 Continuous Girder Bridge, Lachine, near Montreal 34 Rubber strip supported at 4 points, and at 2 points 34 Plate girder bridge 35 Lattice girder bridge, showing rivets 36