Atlantic Steam Navigatmi. 161 



consequence, the direct tendency of these levers, when the power 

 of wind is apphed to their sails,^is to upset, instead of to propel 

 the ship. Hence we find, practically, that when the wind in- 

 creases at sea, the shipmaster's first care is to take in the top- 

 sails, which is nothing more than shortening the levers upon 

 which the power of wind acts. A ship going by the wind is 

 capsized when the power acting upon the levers is greater than 

 the resistance. 



When a ship with her sails set is taken aback, she is hurried 

 stern fii^st into the depths of the ocean from the same cause, and 

 not much time given to think about it, unless the levers are short- 

 ened in time, by taking in the sails, as a change in the position 

 of the ship sufficiently quick, brings the acting power to bear in 

 a different direction. 



If the resisting power of the ship is sufficient to sustain her po- 

 sition on the water, and the levers are forced beyond their strength, 

 then the ship is dismasted, and left, a helpless thing, to the mercy 

 of the storm. The power aj :\'a,ys acts upon vertical levers, and 

 daily practice, in saihng ships, shows the danger. In a steam 

 ship, as such, the power is applied to a combination of short 

 levers, -.acting horizontally upon the body of the ship, and in a 

 direction the reverse of the power of wind upon sails, always pro- 

 l^elling the ship forwai'd, and never losing power by a collateral 

 motion. 



The paddle-wheels of the British Q,ueen are 30 feet in diam- 

 eter, of course about 93 feet in circumference. The floats are 

 about three feet asunder, which will give thirty one sets of floats 

 to each wheel. There are three floats in a cycloidal position in 

 each set, nine and a half feet in the clear in length from one side 

 of the wheel to the other, and one foot in breadth. Hence you 

 will perceive that each set of floats has a superficial area of twenty 

 eight and a half square feet, equal to 873 square feet for each 

 wheel, and 1746 for both. The midship section of the British 

 Q,ueen presents a resistance of 550 square feet to be overcome by 

 1746 feet of the floats. 



The mean speed of the wheels may be taken at sixteen revo- 

 lutions per minute, and at that rate would run 29,760 yards per 

 hoiu-, equal to seventeen miles. If we deduct one fifth, the usual 

 allowance, from the velocity of the periphery, to reduce it to the 

 mean velocity of the wheel, we then have tliirteen and a half 



Vol. XXXV.— No. 1. 21 



