AIR PONTONS AND PONTON BOATS. 137 



facture. The first objection is removed by perforating different 

 parts of the knapsack ; the second, by a change of ingredients 

 in the compound ; and the last, by skill and experience in the 

 manufacture. See plate , fig. . 



MINERS' KNAPSACKS. 



This knapsack is manufactured of gum-elastic plated cloth or 

 vellum, upon the same general plan as the knapsacks before 

 described, with the addition of apartments for the miner's tools. 



GUN AND PISTOL STOCKS. 



Caoutchouc enamel and ivory are admirably adapted, either 

 alone or in combination with iron or wood, for pistol and 

 gun stocks, and also for the handles of other military weapons 

 generally. There is also an important economy in the 

 manufacture of these substances for these purposes, because 

 they are moulded into the different forms, either plain or orna- 

 mental, with trifling labor without waste of material. 



AIR PONTONS AND PONTON BOATS. 



India rubber pontons and ponton boats, by which is here 

 meant all such as are made of India rubber fabrics filled with 

 air only, were among the first things made of gum-elastic by 

 different manufacturers. 



The attention of the United States and other governments 

 was early drawn to them, as being inventions deserving of en- 

 couragement. They were favorably noticed, and orders were 

 given by the United States government for supplies, as then 

 manufactured, of native gum. In the commencement of the 

 manufacture of the vulcanized fabrics, orders were repeated for 

 supplies of the vulcanized pontons ; but they have thus far failed 

 to be as useful as was anticipated. 



