228 On Low Steam Power to Vessels, instead of Sails, [Oct: 



steam for the transport of merchandize at low rates, and the subject is 

 well worthy of investigation. The question is, whether merchandize 

 can be transported at the rate it is at present conveyed by sailing vessels, 

 cheaper or safer by steam ; or whether it can be conveyed at the same 

 cost as in sailing vessels, but quicker by steam. 



It seems strange to conclude, that, because it will not answer to use 

 steam for the common purposes of commerce at high speeds, therefore 

 it will not be advisable to use it at moderate rates. On land, horses 

 are used at high speeds for passengers, and at low rates for goods, and 

 on examination it may be found to be just the same with Steam Power 

 at sea. The two cases are in effect precisely similar ; in moving land 

 conveyances the resistance at higher speeds does not increase, but animal 

 power rapidly diminishes, which is the cause of the rapid increase of 

 cost. In steam vessels, there is indeed no less of power at higher speeds, 

 but the resistance to a vessel moving through the water rapidly increases, 

 and hence the effect is the same as in land conveyance ; viz. a rapid in- 

 crease of expence. In the one case, there is no increase of resistance, 

 but a decrease of power as the speed increases ; in the other there is no 

 decrease of power, but there is an increase of resistance. Hence upon 

 the first glance at the subject, it would appear probable that as it is found 

 to answer on shore to use horses for passengers at high speeds and for 

 goods at low ones, so it may be found in the case of steam afloat. 



The best way of attempting to arrive at a sound conclusion in this 

 case, is, to compare the actual cost of the two modes from the data we 

 have, and then to consider what further important points there are in 

 the matter, which it is not so easy to make subjects of calculation. 



But it may be well first to consider the leading principles, which 

 affect the motion of vessels through water. It is well ascertained that 

 up to about 8 knots, an bour, the resistance of water to vessels increases 

 more rapidly than in the proportion of the square of the velocity ; 

 that is, with a double velocity resistance is more than four times 

 as great, with a treble velocity more than 9 times as great and 

 so on. Hence to move a vessel a certain distance, it takes 

 more than four times as much fuel and more than four times the 

 power of engine to do it at a double speed, and more than 9 times as 

 much fuel and steam power, to do it at three times the rate. This 

 appears to hold good up to a certain speed, about 8 knots an hour, after 

 that the resistance does not increase quite so rapidly, but still in rather 

 a greater proportion than the velocity. Hence if a vessel can carry suf- 

 ficient fuel to go 4000 miles at the rate of ten knots she can carry 

 enough to go about 12,000 at 5 knots, and more than 50,000 miles at 2^ 

 knots. But further, as in going at the double speed the engine must 



