THE CONQUEST OF TIME AND SPACE 



used during submergence a far greater speed would be 

 acquired; but this is out of the question, as such en- 

 gines would consume the air supply of the little boat 

 far too rapidly. The compromise, now adopted uni- 

 versally, is to use gasoHne motors while running at the 

 surface or partly submerged, when the conning-tower 

 is open, utilizing part of their energy meanwhile to 

 charge the storage batteries. 



It is evident, therefore, that no great speed can be 

 expected of the submarine in its present state; and in 

 point of fact the largest type is able to develop only 

 about ten or eleven knots when submerged, and fifteen 

 while at the surface — far below the speed of any other 

 type of war vessel. But the experimental attacks upon 

 the "Yankee" prove that they are dangerous fighting 

 craft, and a recent voyage ,by a flotilla of ItaHan sub- 

 mersibles shows that such boats are no longer harbor- 

 locked vessels. In 1908 the Italian flotilla in question 

 made a voyage from Venice to Spezia, a distance of 

 thirteen hundred miles, without assistance from auxil- 

 iary boats. About the same time a British submarine 

 flotilla, on a three-hundred mile trip, remained sub- 

 merged for forty consecutive hours. The depth of the 

 submergence in this case was only a few feet, but great 

 depths may be reached with relative safety. In one 

 test a Lake boat carrying her crew sank to a depth of 

 one hundred and thirty-eight feet, returning to the sur- 

 face in a few minutes. At another time the "Octo- 

 pus," without her crew, was lowered to a depth of 

 two hundred and five feet, sustaining a pressure of 

 fifteen thousand tons, without injury. 



[116] 



