in orthogonal co-ordinates (a simple indicator system), and a small 

 one, the needle of which moves round an arc of a circle : then two 

 pressure gauges, each with a needle and suitable electric contacts, 

 which actuate apparatus designed to release the ballast, during dives 

 in which the bathyscaphe is not manned but is operated by an auto- 

 matic device. The two graphs (Figs. 13 and 14) show the differences 

 between the recording apparatus. For the first pressure-gauge men- 

 tioned, the time reads from bottom to top ; but while the point of the 

 recording needle in the small one describes the arc of a circle, that of 

 the large one moves in a straight line from left to right when the 

 pressure increases. If the speed is constant the little gauge traces a 

 curved line: the large one, on the contrary, traces a straight line the 

 slope of which depends upon the vertical speed of the bathyscaphe. 

 It is inclined at 45° when this speed is 31 -4 in. per second. This greatly 

 facilitates the piloting of the bathyscaphe and the making of ob- 

 servations. 



These pieces of apparatus must naturally be in communication with 

 sea water; but the sea water must not come in, for it could cause 

 corrosion. In the antechamber is found a vessel full of oil which has a 

 pressure equal to that of the sea water. A steel tube of 0-25 in. (6*3 5 mm.) 

 external diameter and 0-072 in. (i -82 mm.) internal diameter passes from 

 this vessel to the interior of the cabin, where it ends in a distributor 

 which by means of four tubes is connected with the four pressure gauges. 



At the mouth of the distributor there is a high-pressure cock. If 

 one of the pressure gauges happened to leak (which, in fact, never 

 happened) the crew would have to close this cock, disconnect the tube 

 of the defective gauge, screw a stopper in its place, and re-open the 

 cock : this whole operation could be completed in less than a minute. 

 It was the Fiat Company which installed all the tubing in the cabin, 

 employing tubes and unions standardized in the automobile industry, 

 where they are used for the injection of fuel in Diesel engines. It is 

 true that the normal injection pressure of the Diesels is less than that 

 which is found here. But if one compares the operating conditions of 

 lorry engines (the variation in pressure running at each second 

 revolution of the engine from zero to the maximum and vice versa, 

 whence inevitable vibrations are set up) with those of the bathyscaphe 

 where the maximum pressure is only reached gradually and, in prac- 

 tice, only a limited number of times, it is clear that all this tubing 

 would function without failure in the bathyscaphe. 



[96] 



