458 THE APPLICATIONS OF PHYSICAL FORCES. [BOOK iv. 



stroke. In the Minotaur the cylinders are 9 feet 4 inches in diameter, 

 with a 4 feet 4 inch stroke. The cylinders of the Friedland engines 

 have an interior diameter of 2 '10 metres, and the stroke of their 

 pistons is not less than T30 metres. The pressure of the steam is 

 thus exerted for each piston on a surface of about 3*50 square metres ; 

 if we suppose the tension of the steam to be two-and-a-half atmo- 

 spheres, this pressure is equal to 90,000 kilogrammes. To guide 

 pistons of such dimensions, not one only but two or four rods are 

 employed, which articulate by a transverse with the connecting-rod. 



Fie. bll. Side-lever engine of the Sphytix. 



The latter returns upon itself to articulate with the knee of the 

 driving-shaft, performing the function of the crank, and for that 

 reason it is called the return connecting-rod. 



The engine of the Friedland is remarkable not only for its 

 dimensions, its power, and the speed it gives to the ship, which in 

 calm weather is not less than fourteen and a half knots an hour, 

 that is about seventeen and a half miles. Its screw is 6'10 metres 

 in diameter ; it was to be seen in motion in the Paris Exhibition of 

 1867, and any one placing himself in the direction of the motion of 



