ON STEAM VESSELS ADAPTED TO LONG VOYAGES. 69 



ON THE POWER AND TONNAGE OF STEAM VESSELS BEST ADAPTED TO 



LONG VOYAGES. 



The proposed employment of steam communication in voyages of greater length than has 

 hitherto been accomplished, and particularly in the voyage to America, a distance of 3000 

 miles, renders the question of the vessel best adapted to such purpose of great interest, both 

 in this country as well as in America. In fact, a voyage of such length has been hitherto 

 considered beyond what can be obtained by steam power alone, from the difficulty of carrying 

 a sufficient quantity of coal for the consumption of the engine : the improvements, however, 

 which have gradually been introduced, and the success which has attended what has yet been 

 attempted, have given confidence to a sufficient number of individuals to embark in this 

 undertaking, and vessels for the purpose are now being constructed both at London and at 

 Bristol, 1 which will be ready to launch in a few months. 



The voyages which have already been performed, not being of such length that the supply 

 of coals for the engine has been a matter of difficulty, the attention of engineers has been 

 directed rather in giving the greatest speed, than in the greatest capabilities for distance : 

 such vessels must therefore not be looked upon as a criterion of what may be performed : 

 their consumption, speed, &c., will however serve as data by which we may estimate the 

 capabilities of vessels of tonnage and power better adapted to the purpose. 



The larger the vessel, every thing being in proportion, the greater will be her capabilities 

 both for speed and length of voyage : this I will illustrate in a few words theoretically, and 

 then compare it with the practical results. 



The means of stowage of any vessel (which is proportional to the tonnage) will increase as 

 the cube of the linear dimensions, but the sectional area or resistance will increase only as the 

 square ; consequently, if the power be made proportional to the tonnage, an increased speed 

 will be given to the vessel, and consequently the consumption of fuel in a voyage of a given 

 length will be decreased, or length of voyage increased, in the same ratio. 



If the power of the engine be only increased proportionally to the resistance, or immersed 

 section, or the same velocity given to the vessel, the consumption of coals per hour being 

 increased in a less proportion than the means of stowage, it is obvious the fuel will last much 

 longer, and the length of the voyage, both in time and distance, will be proportionally 

 increased. 



To ascertain numerically the amount of the saving in the two cases, let the contents, power, 

 sectional area, and velocity, of any existing vessel, be represented by c, p, a, and v ; and let 

 it be required to find the velocity of a vessel, c, whose power, sectional area, and velocity, we 

 will call p, a, and v. 



Assuming the case of the powers being in the ratio of the tonnage, 



p' = 7- p ; 



and as the section is increased as the square of the linear dimensions, and the tonnage as the 

 cube, we have 



1 This vessel (The Great Western) is now launched, and is arrived in the Thames. 



