269 
Description of a Portable Bridge . 
Intended to be passed, with a sufficient quantity of plank- 
ing posts, chains, &c., according to the existing circum- 
stances of the case, are the whole of its component parts. 
A bridge on this principle for a river, &c., of a con- 
siderable width is very portable ; for several of the square 
frames may be packed upon each other in carriages or 
waggons of the dimensions of eight feet three inches 
long, three feet four inches wide, and as many feet high 
as it may be wished to pack a number of frames ; two of 
them rising one foot. The links and staples can be packed 
in cases, each sort separate. 
The method to be used in passing a river with this 
bridge shall now be described. (A valley is passed in the 
same manner; but there being no water to pass, the 
bridge will be easier supported from the under side.) 
First, two sufficient holes are to be dug on one side 
the river, at the distance apart of the width of the bridge, 
which in this plan is nine feet, and the posts I, are first to 
be prepared with prongs, &c., as in the dotted figure K : 
next the four smaller ones L, properly secured and well 
rammed. Then taking any one of the pieces C. fix it on 
the posts I and L as drawn, and support it on two well 
driven piles, if the shore will permit : and hooking on the 
next piece with one of the links F through the eyes at the 
bottom of the piece, and one of the staples G, fixed into 
the holes of the upright piece or parapet, it will there 
hang. Several more are to be hanged on the same way, 
leaving under them, where necessary, barges or other 
craft, moored with supporters under them fro tempore . 
When completed to the opposite shore, the same process 
of fixing the posts. &c., is to be repeated, and when fas- 
tened to these posts, the under supports may be taken 
away, and the whole left suspending by itself. Nothing 
now remains but for the superintendent of the work to 
screw the staples, by the handspike H, till the bridge ri- 
