MERITS OF INDIA RUBBER. 



663 



until, in 1830, the discovery of india-rubber afforded the op- 

 portunity which was immediately made use of, to improve the 

 diving apparatus. Various improvements, some of them pro- 

 tected by patent rights, have been made in the construction of 

 this submarine armor, but as peifect a' method of making it as 

 any is that designed by two Frenchmen, M. Eouquarol, a min- 

 ing engineer, and M. Denayrouze, a lieutenant in the French 

 navy. One of the chief merits of this arrangement is that by 

 which the supply of air is furnished the diver. This appar- 

 atus the diver carries on his back, and it consists of a reser- 

 voir made of steel or iron, capable of resisting great pressure, 



GRAPPLING MACHINE. 



with a chamber on its top constructed to regulate the influx 

 of the air. A tube from this chamber, terminating in a mouth- 

 piece, is held between the diver's teeth. This pipe is furnished 

 with a valve permitting the expulsion of air, but opposing the 

 entrance of water. The steel reservoir is separated from the 

 chamber by a conical valve opening from the air chamber in 

 such a way as to open only by the force of exterior pressure, 

 that of the air in the reservoir tending to close it. The 

 air from the air-pump is forced into the reservoir, and from 

 this the diver supplies his needs as follows: The air-chamber 

 is closed by a movable lid, to which is attached the tail of the 

 conical valve. The diameter of the lid is a little less than the 

 int°rv">r diameter of the chamber, and it is covered with india- 



