that adopted in connexion with the plan heretofore recognized in my patents.

In further explanation of the suspension bridge, reference is made to the accompanying drawings; which will illustrate more clearly the manner of constructing the suspension bridge and the arrangement of its parts.

Should it be regarded as an object of importance to give to the main braces of the suspension bridge an equable action in all the panels of a bridge, the following rules should be observed and the object in view will be approximately accomplished. Let the extent of the bridge span, between the abutment or pier supports, be 120 feet, and the height of the truss frame, or rather the distance from centre to centre of the strings, be fifteen feet. Now, commencing at either extremity of the span, the first panel should have a distance measured on the strings, from centre to centre of the posts, equal to 5 feet, the second panel, a distance of 6 feet, the third equal to 7 feet, the fourth, 9 feet, the fifth 13 ft., and the sixth 18 feet, making the aggregate extent of the half span, equal to 60 feet. By this arrangement all the main braces respectively will be subjected to an action nearly equable, and their greatest possible efficiency may be rendered available. The diagrams, hereinafter referred to, will serve to illustrate this arrangement, and guide the builder. This method of adjustment, by means of which a uniformity of action may be given to all the main braces of a truss-frame, respectively, is also claimed as new and original, not only with respect to the construction of wooden bridges, but also with respect to bridges composed of iron, or partly of iron and partly of wood; which may be constructed of similar parts nominally, though these parts may all differ in shape, dimensions, and manner of attachment to each other, all of which may be varied according to circumstances.

In the accompanying drawings, fig. 5, (see front page) A, B, C, D exhibits a side view of a portion of a truss frame of my suspension bridge, attached to its abutment; and fig. 6, shows a similar side view of a part of the truss frame, on an enlarged scale, for the purposes of exhibiting its construction the more clearly. C, D, is the arch brace, which bears upon the abutment as shown at C,

fig. 1; n, n, n, in the same figure, represent gibs and keys, which pass through and firmly connect the respective thicknesses of timber, of which the arch brace connects below the lower string piece. The space between the two thicknesses of timber of which the arch brace consists, is filled in with what may be denominated a splicing piece, the whole being confined together by bolts, gibs and keys, or treenails.

G, G, are the posts which extend vertically, and have their ends bearing against the lower and upper stringpieces, against which they abut. At d, d, between the upper ends of these posts and the upper string-pieces, there are counter wedges, which when driven in, necessarily cause these posts to act upon the string-pieces by direct thrust, which causes the main and counter braces to act by tension instead of thrust.

The string-pieces consist each of three thicknesses of stuff, as shown in the top view H, fig. 7, and the main suspensor braces E, E, fig. 6, occupy the spaces between the central and outer stringpieces, as above stated, and extend seveinches above the upper, and below the lower string-pieces; the five thicknesses composing the braces and string-pieces being secured together by treenails passing through them. The first of these braces extends from the head of the first set, to the floor of the second set of posts, and so on to the centre of the bridge, where their direction is reversed. The counter extension braces are shown at F, F, fig. 6. These consist each of a single piece of stuff, which passes obliquely between the two which constitute the main braces, abutting against the middle timber of the string-pieces, and confined at each of their ends between the main braces and posts, by means of treenails, or other analogous devices.

Fig. 7 exhibits a horizontal and vertitical section of a portion of one of the strings, and shows the manner of connecting the posts, main, and counter braces with the strings. The shades in the upper part H, of this figure, indicate sections of the posts, main, and counter braces at the upper edge of the lower string, and by inversion, at the lower edge of the upper string. E, F, and G, designate the same parts as in fig. 2.

In fig. 10, (p.325) A, B, C, D, is a vertical diagram, intended to exhibit the relative

dimensions of the panels of a truss frame for my suspension bridge, so graduated as that the stress, or action upon the main suspensor braces, may be respectively equal in every part of the frame. a, a, are the posts; b, b, the main suspensor braces, and c, c, the counter suspensor braces. P, P, are the abutments or piers of the bridge. Fig. 11 (p.325), shows the manner of applying the lateral braces, in order to afford a corresponding action laterally between the string pieces a, a, a, a; it will be seen from an inspection of the figures, that the extent of the panels as measured on the strings, increases as measured from the extremities towards the centre of the span of the bridge.

The straining or trussing of the truss frames is effected by driving the counter wedges above mentioned, which are situated, as shown in the drawing, between the upper end of each post, and the upper string piece, but which may, if preferred, be situated between the lower ends of said posts, and the lower stringpieces.

This operation is calculated to elevate the upper string at the points where the main braces are attached to it, and of course to increase the tension of the main braces of the adjacent panel. Every movement of tension thus produced is counteracted by a corresponding degree of antagonal tension in the counter braces, thence the main and counter braces act by tension instead of thrust, and the posts by thrust instead of tension.

Having thus fully described the manner in which I construct my suspension bridge, I do hereby declare that what I claim as new therein, and desire to secure by letters patent, is the manner in which I have combined the posts, the main braces, and the counter braces, as herein set forth, so that by wedging up the the posts between the upper and lower string-pieces by wedges, or counter wedges, the thrust of the posts shall cause the main and counter braces to operate by tension, and thereby to sustain the bridge; the main braces, the counter braces, and the posts being connected with each other, and with the string-pieces in the manner described.

I will here remark that although I have mentioned the strings of my bridge as each composed of three pieces, this number may be increased, if desired;

the number of pieces of timber in the respective braces, &c., being made to correspond therewith.

The Brace Bridge.

The several parts of the brace bridge to which said improvements relate, are the strings and their splices, the posts, the main braces, the counter braces, and the arch braces of a truss-frame; and also the manner of trussing or straining the truss-frames.

These parts in the structure herein described, vary materially in their relative, and especially in the transverse, dimensions of the timber used from those contemplated and described in bridges previously patented. Instead of timbers of various sizes, and of nearly a square form, the several parts alluded to are to be uniform, or nearly so in all their transverse dimensions, a transverse section of each timber of all the parts having the form of a parallelogram, varying from two to four inches, by eight to twelve or fifteen inches, according to the length of the bridge span, the weight of the load to be sustained upon the bridge, and other circumstances connected with these considerations.

Instead of notches or recesses in the string-pieces and posts, by means of which these parts are locked together, and instead of wedges at the insertions of the posts between the string-pieces, the connexions between the posts and strings are effected by means of gibs and keys passing entirely through the strings transversely thereof, and at the same time resting in notches, prepared for the reception of the gib and key, in the back of the post, or in the side opposite to the points or steps at which the main braces communicate their thrust against the posts; the notches serving to regulate and maintain the relations with respect to distance, between the upper and lower strings, the gibs serving to clamp the string-pieces together and the keys serving not only to confine the strings to the posts; but also, to impart the requisite trussing to the truss frame, and at the same time to force the counter braces into appropriate action.

Joggles, or pieces of timber about two feet long, three inches thick, and three or four inches wide, are inserted in the spaces between the string pieces, and immediately behind the posts, for the purpose of aiding the gibs and keys in