378 GOODYEAR ON GUM-ELASTIC. 



The construction of these pontoons is such, that they will not 

 collapse or be rendered unsafe in consequence of a leak, unless 

 it happens to be a large one upon the water-line ; neither is it 

 indispensable that the tube or orifice should be stopped, in order 

 to keep them inflated. See plate , fig. 



SELF-INFLATING PONTOON RAFT. 



This raft may be formed from any description of air cylinder 

 represented in plates , figs. . But the kind which is 

 decidedly best adapted for this use, is the self-inflating pontoon 

 described in this chapter. 



In order to form one of these rafts, two of these pontoons or 

 balsors are inflated and kept distended by a spar between them, 

 to which they are fastened at each end. They are kept at any 

 suitable distance apart by a transverse spar at both ends of the 

 raft. 



An India rubber canvas is drawn under them, which enables 

 them to carry a large freight in smooth water without danger of 

 its being wet ; or, if the canvas is made larger, and is allowed to 

 fall far below the cylinders, the raft will float a much larger 

 freight or a much greater number of persons safely, in proportion 

 to the bulk of the freight. 



Rafts of this kind may be recommended as the surest and 

 most economical means of saving the greatest number of lives 

 and the largest amount of property, in cases of accident so de- 

 structive to both, and so very frequent upon navigable rivers and 

 lakes. They are not expensive, and occupy but small space — 

 say three feet by six — for one large enough to save the lives of 

 three hundred persons. They are extremely light. There is 

 not the slightest danger of the cylinders collapsing, and they can 

 be fitted for use and launched in two or three minutes, without 

 difficulty. 



