34 ANNUAL OP SCIENTIFIC DISCOVERY. 



ShQ is supplied with eight boilers, each having five furnaces ; and at 

 fvill speed, which is about twelve knots, consumes one hundred and two 

 tons of coal per diem. 



The boilers and machinery take in the length of the hold, 82 feet, which, 

 for a nominal power of one thousand horse, is considered excessive. 



The results of the trial of the Napoleon have sufficiently established the 

 fact of the practicability of so adapting a propeller to a ship of the largest 

 class as to insure great speed, and form a most effective man-of-war, for cer- 

 tain purposes and in certain situations ; but when the great weight of the 

 engines and coal is considered, and the great space they necessarily occupy 

 in the vessel, (thereby diminishing the stowage of provisions and water,) 

 and when we further reflect that after the coal is expended the ninety- gun 

 ship has only the spars and sails of a sixty-gun ship to rely upon, we are 

 forced to the conclusion that, however useful such a vessel may be for 

 short passages, and in those seas where her supply of coal and provisions 

 may be constantly replenished, yet that her sphere of action must be very 

 limited, and that she could not be relied upon for the long cruises and 

 various service on which an ordinary line-of-battle-ship is employed. 



A ship constructed on the model of the Napoleon, for the sake of gain- 

 ing a speed of ten or twelve knots per hour for the distance of about 2,400 

 miles, is compelled to sacrifice a great part of her efficiency in several 

 other most important particulars. 



In time of war, at short distances from port, for the defence of harbors 

 and bays or the Florida Channel, and for the general purpose of defending 

 a coast, to force a blockade, or for the speedy transport of troops to an 

 adjacent territory, such a vessel would undoubtedly be a most valuable 

 acquisition to our navy ; but her employment must necessarily be confined 

 to such situations and circumstances, for should she be unlucky enough 

 to fall in with a hostile squadron with her coal expended, or with her 

 machinery rendered useless by any of the numerous accidents to which 

 steam machinery is constantly exposed, with her comparatively light rig 

 and her want of stability, the consequence of losing so great a weight of 

 coal, she would prove any thing but a formidable antagonist ; and it is 

 much to be feared that she would be compelled to strike to any vessel of 

 her class that should attack her. 



In France and England the question of adapting propellers to their men- 

 of-war already existing, particularly to line-of-battle-ships, has excited 

 the deepest interest, and has been discussed in all its bearings. In both 

 countries great efforts have been made to ascertain how this adaptation 

 could be effected at the least expense, without injury to the sailing quali- 

 ties and capacities of the ships, and to discover the best general plan for 

 the necessary alterations. 



After a series of the most careful trials, made at the naval station of 

 Roche-fort, it was found that there were insurmountable objections to 

 placing an engine of six hundred and fifty-horse power on board a hun- 

 dred gun-ship. It was then determined to try the experiment with the 



