OF IRON BEAMS. 485 



part an ellipse, and Uieir bottom rib of equal 

 breadth throughout 



XXII. EXPERIMENT. 



This beam was of the common form, from 

 the same model as before, for comparison with 

 the three preceding ones. 



Distance between supports as before. 



DimensioDB of section in inches. 



Thickness at A = .30. 



,, „ B = .42. 



„ „ C = .45. 



DE= .51. 



FE = 2.28. 



Area of section = 3.17 inches. ^ ^ 



Weight of beam = 40 lbs. 



This beam bore 8965 lbs. and broke in the 

 middle with considerably less than 9327 lbs. 

 a man supporting part of this extra weight by 

 a lever. This accident prevented the exact 

 determination, but I believe 9146 lbs. the mean 

 between the numbers above, to be very near 

 tlie breaking weight, perhaps rather above it. 



Hence strength per square inch of sectioif 

 ir.^ a: 2885 lbs. 



.46. It has been doubtless remarked that, in most 



