OF IRON BEAMS. 495 



the breadth of the bottom rib was 3.85 inches. 

 Now, by the property of the lever, the pressure, 

 which the whole beam bore, is, to the weight 

 which the half beam broke as above, should 

 have borne, as 2 to 3. Hence 2:3:: 13543 lbs. 

 (weight borne by whole beam) : 20314 lbs. 

 = weight, which the half beam should have 

 borne : but it required 23396 lbs, to break it ; 

 hence a parabolic beam similar to that above, 

 7 feet 6 inches long, and broke by props 7 feet 

 asunder, is rather too strong toward the ends; 

 and it would have been too strong there still, if 

 the props had been 7 feet 6 inches distant, or 

 at the ends of the parabolic base of the beam. 



54. The other half of the beam was turned 

 the wrong way up, and broke by weights 

 gradually laid on its middle or half way between 

 the props, one prop supporting the end of the 

 beam, as before, and the other placed 3 feet 

 3 inches from it. It broke in the middle with 

 13356 lbs. or 5 tons 19J cwt. 



If we reduce this weight to what it would 

 have been if the distance of the props had 

 been 3 feet 6 inches as above, we have, 3 feet 

 6 inches : 3 feet 3 inches, or 14 : 13:: 13356 : 

 12402 lbs. or 5 tons, lOJ cwt. which is little 

 more than i of what the former half beam 



