138 GOODYEAR ON G U M- EL A S T I C . 



The objections which apply to boats and pontons made of 

 gum-elastic fabrics (uncombined with other materials, for stay- 

 ing and stiffening them) and filled with air only, are the follow- 

 ing, viz. : They require to be filled with a hand bellows, which is 

 an inconvenient and laborious process. A very small leak will 

 cause them to collapse and sink. These difficulties are over- 

 come by combining the vulcanized fabrics with other materials, 

 in the manner specified in this work for constructing self-inflating 

 air- work. See Chapter , p. 



From these descriptions, and those given in the chapter on 

 self-inflating pontons, the improvements here alluded to may be 

 understood. A brief description is here given of a few of the 

 many forms of pontons and boats which are filled with air only ; 

 not for the purpose of recommending them, but for the purpose 

 of giving an idea of the origin of articles of this description. 



AIR PONTONS. 



The air ponton above alluded to as ordered by the United 

 States, was made of coated canvas, in three compartments 

 cemented together, as represented, plate , page , each 

 compartment being inflated by a separate tube, forming together 

 a raft or boat about six feet wide and eighteen feet in length. 



PONTON AIR BOAT. 



This boat is formed of a series of air-tubes or cylinders, each 

 of which is inflated with a separate tube. This, together with 

 the ponton above described, may be considered the best among 

 the many kinds of air pontons and boats designed to be filled 

 with air only. See plate , fig. . 



