OF IRON BEAMS. 463 



There had been -i- gained in strength, above that 

 of the common beam, by the addition already 

 made, and it was probable, we might add still 

 more to the lower rib without danger of fracture 

 by compression; for in no case except of the 

 common beam, which sometimes twisted a little 

 before it broke, had there been the slightest 

 appearance of over compression. This idea 

 will be pursued in our future experiments. 



X. EXPERIMENT. 



Common beam, cast upside down, in the usual 

 manner. This like the rest was from the same 

 model as that in experiment 4. 



Distance between supports as before. 



Dimenaioni of section in inches, (see section in expt. 4). 



Thickness at A = .29 

 „ B=A25 

 >, „ C =. .46 



FE = 2.3 

 DE = .53. 

 Area of section = 3.1 § inches. 



A^oftf.'^The three castings in experiments 8, 9 and 10, were 

 all broke at 4 feet distance between the props, on account of 

 there being defects near the ends of two of the castings, the 

 weight however was laid on the middle of them, 3 inches being 

 taken off each end. The real breaking weights were 9296, 12068 

 and 9926 respectively ; those given above being the retluced 

 ones to a span of 4 feet 6 inches. From the above cause, the 

 deflections are neglected. 



