10 Description of a Portable Bridge. 



the state of a prismatic coal. — Their weight was 33 grams, 

 Loss in distillation 207 grains. 



Component parts : Volatile matter 86*23 

 Oxide of carbon 13*75 



100 parts. 



[To be continued.] 



II. Description of a Portable Bridge, invented hy Mr. 

 James Elmes, Architect, of College-Hill, Queen-Street, 

 Cheap side, London *. 



JlSiudges upon this construction may be rendered either 

 permanent or otherwise. The only difference will be, that 

 for the former the parts may be strongly bohed and fastened 

 together, instead of being joined by contrivances which ad- 

 mit of the parts being separated, for the convenience of re- 

 moval, as in the drawing now sent. (See Plate I.) 



The component parts shall be first described, and after- 

 wards 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 flat upon the bottom for conve- 

 niency of packing, as shown by the figure C. A skirting 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 skirting 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 de- 

 scribed round its superficies working in an interior screw, 

 contained in a box, opening and closing very considerably 

 by a single revolution of the box round the screw, by the 

 means of a small handspike H. 



* Communicated by the inventor. 



As 



