THE WORLD'S ADVANCE 



159 



that our under-water craft never pur- 

 posely go to their maximum designed 

 depths after their one constructors' trial. 

 This is a serious state of affairs, be- 



boats are put; the tube filled with water 

 and closed ; and then hydrostatic pressure 

 is applied by suitable pumps. Gradually 

 the pressure is raised within the tube, and 

 the water enveloping the sub- 

 mersible tries to crush the boat 

 just as the sea would exert itself 

 at the equivalent depth. But 

 wait ; this is not all. 



There are observers inside of 

 the submarine who can see for 

 themselves exactly where leaks 

 occur, and they are not endan- 

 gered, because they are in con- 

 tinual telephonic communication 

 with the engineer at the dock's 



Two Views of the Entrance to the 

 Testing Dock, Showing the Globu- 

 lar Caisson in Place. After a Sub- 

 marine Has Been Placed in the 

 Testing Compartment, Hydrostatic 

 Pressure is Gradually Increased by 

 Means of Pumps, So as to Submit 

 the Walls of the Under-water Craft 

 to the Same Conditions as if it 

 Were at a Corresponding Depth 

 Below the Surface of the Sea. 



cause the Germans have shown us how 

 important it is for the submarines to be 

 able to sink to the ocean bottom to give 

 the crews a chance to rest from their 

 nerve-racking work. Again, it is vital- 

 ly necessary that the boats should be fre- 

 quently examined under submerged con- 

 ditions, and this can not be done in a 

 dry-dock. What, then, is the remedy? 

 The Italians have answered this urgent 

 need. 



The famous shipyards of the Fiat-San- 

 Giorgio near Spezia, builders of the not- 

 able Laurenti submersibles, have evolved 

 a special type of submarine testing dock 

 consisting fundamentally of a big tube 

 fashioned of high tensile steel perma- 

 nently sealed at one end and closed at 

 the other by means of a globular cais- 

 son seated against an annular gasket of 

 heavy rubber. Into this dock all of their 



pressure pump. Instantly the pressure 

 of the enveloping water can be released. 

 Thus, right at the building yard, a sub- 

 mersible can be tested under physical 

 conditions that actually reproduce those 

 of a deep submergence, and it is not 

 necessary to wait for the weather or to 

 go hunting for some out-of-the-way hole 

 along the coast. More than this, boats 

 can be frequently tested in this way 

 should be, in fact and all of their emer- 

 gency apparatus, such as automatic blow- 

 outs for the quick expulsion of water- 

 ballast and pumps designed to work 

 against great heads of water, can be put 

 through their paces to see that they are 

 fit and capable. To-day our sailors and 

 officers* have to take a good deal of this 

 readiness for granted ! 



Some years ago a French boat was lost 

 because a pebble was jammed in one of 



