Military Bridges^ and the Passage of Rivers. 299 



the Arch-Duke Charles of Austria, and the Duke of Welling- 

 ton, for which we must refer to the work itself. 



The fifth section contains a dissertation on Bridges or Rafts 

 of Timber, Casks, Air-tight Cases, and Inflated Skins. In ad- 

 dition to the method of constructing rafts, a variety of useful 

 rules for finding the contents of beams, and valuable tables rela- 

 tive to their contents and specific gravity, are subjoined. An 

 article on guaging, or determining the capacity of casks, in or- 

 der to obtain their buoyancy, is likewise recorded. Inflated bags, 

 made of the skins of animals, were even suggested by theRhodian 

 to Xenophon, to enable him to pass the Tigris ; and Alexander 

 had recourse to this method in order to pass the Ox us. Livy tells 

 us that some of HannibaPs Spanish infantry passed the Rhone 

 by swimming, with the assistance of inflated leathern bags, and 

 Caesar informs us, that the Spanish light infantry practised this 

 method of passing rivers, as is at this day employed on the Ti- 

 gris and Euphrates. Canvass-bags, lackered over with a solu- 

 tion of caoutchouc (Indian rubber), have lately been proposed, 

 and in India, basket-boats, covered with undressed hides, are of- 

 ten employed. In short, the extent and variety of information 

 relative to these more temporary expedients can only be duly 

 appreciated by those employed in such operations, to whom the 

 examples will prove invaluable. 



Our attention is next directed in section sixth to Carriage- 

 Bridges and Suspension-Bridges. Carriage-bridges are sup- 

 ported on four-wheeled carriages, and are found to be very use- 

 ful in expeditiously forming temporary bridges in small shallow 

 rivers and canals. Sir Howard does not recommend the Pofit- 

 volant of the Aide Memoire, a French book similar to his 

 own, but there is no doubt that the ordinary carts and waggons 

 of a country may be sometimes found very useful for such pur- 

 poses. A carriage-bridge for infantry, two abreast, was made 

 across the Douro, between Tordesillas and Toro with the 

 spring-waggons of the army. The bottom of the river was hard 

 and even; the average depth being from three to four feet. 

 The waggons were placed longitudinally, at distances suited to 

 the lengths of the planks that had been collected for flooring, 

 which were laid from waggon to waggon, the tail and front 

 boards being taken out. The same thing may be done with the 



