^68 Description of a Portable Bridge . 
No. 35 . 
Description of a Portable Bridge , invented by Mr. James 
Elmes, Architect, of College-Mill, Queen- Street, 
Cheap side, London 
(With a Plate.) 
BRIDGES upon this construction may be rendered 
either permanent or otherwise. The only difference will 
be, that for the former the parts may be strongly bolted 
and fastened together, instead of being joined by contri- 
vances which admit of the parts being separated, for the 
convenience of removal, as in the drawing now sent. 
(See plate 7-) 
The component parts shall be first described, and af- 
terwards the manner of applying them. A is a strong 
iron frame that forms the bottom. B is a square frame of 
the same metal, fastened by hinges, to the ends of A, for 
the purpose of falling down fiat upon the bottom for con 
veniency of packing, as shown by the figure C. A skirt- 
ing of iron plate marked D, is also strongly fixed to the 
bottom, as in the elevation of the whole P, and in the 
figure B. Two spring catches are attached to this skirt-, 
ing to keep the sides steady when erected. One of these 
catches E on a larger scale is shown in the drawing. 
The remaining detached parts are marked F and G. F 
is a square iron link separated in the middle, and each 
part opening by a spring. G is a kind of staple opening 
and closing by a double worm described round its super- 
ficies working in an interior screw, contained in a box, 
opening and closing very considerably by a single revo- 
lution of the box round the screw, by the means of a 
small handspike II. 
As many of each of the above described parts as are 
necessary, according to the width of the river or valley 
* Tillocb, vol. 33 j p. 10. Communicated by the inventor. 
