SELF-INFLATING PORTABLE LIFE-BOAT. 375 



is made of plated canvas. The ribs or knees and braces which 

 are made either of iron or wood, covered with caoutchouc 

 whalebone, are cemented to the boat cover upon the inside. The 

 ribs or knees are kept in place when the boat is opened by braces 

 extending from one rib or knee to the other, and also by a keel- 

 piece in the bottom of the boat. The ribs, keel, and braces of 

 the boat, which are represented by fig. 2 are cemented on the 

 inside of the boat in the same way as those of fig. 1, but they 

 are made to run longitudinally with the boat ; when folded, the 

 ribs fit one within the other, so that this boat occupies a smaller 

 space in thickness than fig. 1 ; when opened, the ribs are sup- 

 ported by braces extending from the keel to the gunwale. 



PORTABLE LIFE-BOAT. 



The portable life-boat represented by fig. , is made of caout- 

 chouc whalebone board, and constructed in the same way as the 

 ship's boats described in Chap. ; the gunwales, ribs, and 



seats being made of tubes or cylinders of whalebone board, of 

 such dimensions as will render the boats more or less buoyant in 

 proportion to their size. Compartments of the same material 

 are made in the bow and stern of the boat, air-tight. The keel 

 is also formed of a cylinder, so arranged that it may be filled with 

 water, to give ballast to the boat, and pumped out when neces- 

 sary. See plate , fig. 



SELF-INPLATING PORTABLE LIFE-BOAT. 



These are also of two kinds, resembling each other as the two 

 portable boats before described. They are, in fact, the same 

 boat, with the addition of a tube or air-chamber made of plated 

 fabrics, between the knees or ribs of the boat. Instead, how- 

 ever, of the ribs or knees being made of iron or wood, they may 

 be dispensed with by making the divisions between the tubes or 

 air-chambers of caoutchouc whalebone, of suflicient strength to 



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