><l r I IMA JUNE NAVIGATION. 



165 



concealed, and how shall the crew endure the excessive temperature 

 to which coal fires with little ventilation would subject them? For- 

 tunately, the problem of power for propulsion is much simplified by 

 the fact already mentioned, that for the most part, even a submarine 

 boat lives and moves and has its being on the surface. When at the 

 surface, steam power may be used as on any boat. Many of the earlier 

 boats were thus equipped with boilers and steam engines. These 

 served not only for surface propulsion, but were used also to store up 



Fig. 0. Sketch of the 'Argonaut' as She Might Appear at the Bottom of the Sea. 



energy in the form of electricity or compressed air to be available as 

 power when diving. 



Nowadays gasoline and oil motors have been so perfected and 

 they allow such economy of fuel space and withal such freedom from 

 the dust, smoke and heat incident to a steam plant that they are com- 

 ing into very general use, both afloat and ashore, where moderate 

 amounts of power are required. Both the 'Holland' and the 'Argo- 

 naut' are equipped with gasoline engines. As these require for their 

 operation much larger quantities of air than can be conveniently sup- 

 plied from compressed air tanks, wherever concealment is necessary 



