1851 Great Exhibition: Official Catalogue: Class VII.: John H. Sadler
61. SADLER, JOHN H., Leeds — Inventor and Patentee.
A bridge for railways or other purposes, composed of a series of girders balanced upon piers, presenting singly the appearance of the letter T. The entire bridge is composed of a chain of these girders and piers, TTT; the girders are firmly locked together at the centre of the arch, each having teeth, like those of a spur-wheel, cast on both sides at each end, and plates with similar teeth cast on them, which are nicely fitted, teeth within teeth, and bolted firmly together, making a very strong joint; the bolt-holes through the girders being made oblong, an allowance for contraction or expansion is provided.
[A continuous beam, or bridge girder, resting on several piers, is stronger than if the girders were disconnected at their points of support, in the proportion of about 5 to 3. —S. C.]