162 Sir William H. White [June 9, 



formation of explosive mixtures of gas and air, otherwise accidents 

 must follow. 



Little information is available as regards the success of "peri- 

 scopes " 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 work- 

 ing abroad as well as in this country, it would appear that considerable 

 success has been obtained with these optical instruments in compara- 

 tively smooth water. It is also asserted that when the lenses are 

 subjected to thorough washing 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 experience 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 instru- 

 ments. Improvements are certain to be made as the result of experi- 

 ence 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 unavoidable 

 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 favour the construction of so-called surface-}) oats rather 

 than submarines. They would resemble submersibles in many re- 

 spects, but the power of diving would be surrendered, although they 

 would be so constructed 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 unquestionable that improvements 

 in or alternatives to internal combustion engines will favour the 

 increase of power in relation to weight, and so will tend to the pro- 

 duction of vessels of higher speed. The comparatively slow speed of 

 existing submarines as compared with destroyers and torpedo-boats 

 of ordinary types admittedly involves serious limitations in their 

 chances of successful attack on vessels under way, and higher surface 

 speeds are desirable. 



