Steam Poiver in maintaining a Ferry. 63 



own construction. The water opposed to her paddles is the 

 fulcrum against which her power acts, to carry her forward ; 

 it has been found, by experiment, that these paddles ought not 

 to dip above 18 or 20 inches in the water; consequently, the 

 efficiency of the fulcrum is in the direct ratio of their breadth ; 

 and, all that it comes short of balancing the opposition made to 

 the boats passing through the water, is just lost power, — power 

 employed in displacing the water, not in moving the boat. 

 This loss, too, is more considerable than may be perhaps ima- 

 gined. In rowing-boats, even in ordinary circumstances, it is 

 considered equal to one-third of the whole effort ; and is not 

 probably less in any steam-boat. While in some it must be a 

 great deal more, — as witness the quantity of water which they 

 throw up behind them ; and the absolute stand still to which 

 they are brought even in very ordinary circumstances of wind 

 and sea, — their power at the same time still adequate to its 

 work, still turning the paddles at the usual rate. 



It must next be observed, however, that steam -boats, which 

 are intended to embark carriages and passengers alongside a 

 pier, are necessarily much limited as to the breadth of their pad- 

 dles ; they are thus limited for the sake of convenience ; and 

 also, for a still more cogent reason. They carry their cargo on 

 deck, — their centre of gravity, when laden, is consequently 

 high, they roll deep, and their paddles must be light in propor- 

 tion. Twin-boats also, like those on the Dundee Ferry, ply 

 their paddles at best to great disadvantage, in the dead water 

 between the two boats ; for the sake of strength in their own con- 

 struction, they must have them comparatively narrow; and their 

 bulk is enormous, and must encounter much opposition in passing 

 through the water, particularly with a head wind. An extreme 

 case may, therefore, easily be conceived, with respect to each of 

 these descriptions of boats, in which a deficiency of moving 

 power may be the defect, and yet an increase of it in the engine 

 be no improvement ; and steam-tugs alone seem to have no su 

 milar disadvantages to encounter. They may work their pad- 

 dles in the best May ; they may have them of any breadth for 

 c-onvenience ; and, although there is no doubt a limit, beyond 

 which a variety of circumstances of weather and sea will not al- 

 low them, by any means, to be carried, still tugs, the centre of 



