SUBMARINE NAVIGATION 273 



batteries can be recharged, air compressed and other auxiliary services 

 performed independently of any ( mother ' ship. At the same time, it 

 is desirable to give to each group of submarines a supporting ship, serv- 

 ing as a base and store depot, and this has been arranged in this country 

 as well as in France. With gasolene engines, care must be taken to 

 secure thorough ventilation and to avoid the formation of explosive 

 mixtures of gas and air, otherwise accidents must follow. 



Little information is available as regards the success of ' periscopes ' 

 and other optical instruments which have been devised for the purpose 

 of enabling those in command of submarines to obtain information as 

 to their surroundings when submerged. In this department secrecy is 

 obviously desirable, and no one can complain of official reticence. 

 From published accounts of experimental working abroad as well as 

 in this country, it Avould appear that considerable success has been 

 obtained with these optical instruments in comparatively smooth water. 

 It is also asserted that when the lenses are subjected to thorough wash- 

 ing by wave-water, they remain efficient. On the other hand, the 

 moderate height of the lenses above water must expose them to the 

 danger of being wetted by spray even in a very moderate sea, and ex- 

 perience in torpedo-boats and destroyers places it beyond doubt that the 

 resultant conditions must greatly interfere with efficient vision. In 

 heavier seas, the comparatively small height of the lenses above water 

 must often impose more serious limitations in the use of the periscopes 

 and similar instruments. Improvements are certain to be made as the 

 result of experience with these optical appliances, and we may be sure 

 that in their use officers and men of the Royal Navy will be as expert 

 as any of their rivals. But when all that is possible has been done, it 

 must remain true that increase in offensive power and in immunity 

 from attack obtained by submergence will be accompanied by unavoid- 

 able limitations as well as by special risks, resulting from the sacrifice 

 of buoyancy and the great reduction in longitudinal stability which are 

 unavoidable when diving. These considerations have led many persons 

 to favor the construction of so-called surface-boats rather than sub- 

 marines. They would resemble submersibles in many respects, but the 

 power of diving would be surrendered, although they would be so con- 

 structed that by admitting water by special tanks they could be deeply 

 immersed and show only a small target above the surface when making 

 an attack. There would be no necessity in such surface vessels to use 

 electric motors and storage batteries, since internal combustion engines 

 could be used under all circumstances. Hence it would be possible- 

 without increase of size to construct vessels of greater speed and radius 

 of action and to simplify designs in other important features. It is 

 not possible to predict whether this suggestion to adopt surface-boats: 

 rather than submersibles will have a practical result ; but it is nn- 



VOL. LXVIII. — 18. 



