ON NA VAL ARCHITECTURE. 293 



experimental apparatus at Torquay. We do not believe that the 

 resistances of the ships will accord exactly with those 3f their modeu, 

 but we are satisfied that the behaviour of the models as to resistance 

 approximates very closely to that of the ships in smooth water. But 

 even when we have obtained the best form for resistance in smooth 

 water, it is quite certain that that will not be the best form for service 

 among waves ; we are still open to the corrections of practice and 

 experience at sea. 



The Admiralty are building fourteen-knot ironclad ships with only 

 four and a-quarter beams in the length ; and shallow draft, nine knot 

 unarmoured vessels, with only three and a-quarter beams in the length. 

 The Admiralty experiments at Torquay are also directed towards the 

 discovery of the causes of the enormous loss of power in propelling 

 machinery indicated by the fact that only about thirty-seven to forty 

 per cent, of the maximum power of the steam delivered in the 

 engines is useful in propelling the ship. It is proposed to continue in 

 H.M.'s ships tried at the measured mile, the experiments commenced 

 by Mr. Denny, of Dumbarton, with this object. 



The present condition of the case appears, according to Mr. Froude's 

 estimate, to be that, calling the effective horse-power (that is, the power 

 due to the net resistance) 100, then at the highest speeds the horse- 

 power required to overcome the induced negative pressure under the 

 stern consequent on the thrust of the screw is 40 more ; the friction of 

 the screw in the water is 10 more ; the friction in the machinery 67 

 more; and air-pump resistance perhaps 18 more; add to this 23 for 

 slip of screw, and we get that, in addition to the power required to 

 overcome the net resistance = 100, we need 40 + 10 4- 67 + 18 + 

 23, making in all 158, i.e. t at maximum speeds the indicated power of 

 the engines needs to be more than two and a-half times that which is 

 directly effective in propulsion. 



I regret that the present practice of naval architecture has a side 

 about which I would rather say nothing, but which is yet, in my judg- 

 ment, so important that I do not feel justified in passing it by in silence. 

 That dark side is the tendency of keen competition among owners, and 

 consequent lowness of freights, to make them content with ships built 

 without that regard to their safety in the matter of division into com- 

 partments, which I hold to be in the highest degree desirable. 



