410 



REPORT — 1856. 



39,935 lbs. to the square inch, whereas the same plate torn asunder across 

 the fibre sustained a force of 45,680 lbs. before breaking. This difference 

 of strength can only be accounted for by some defect not perceptible when the 

 fracture was examined. The difference of strength, at the temperature of 

 boiling water, indicated by these two specimens, is as 178 : 203, or in the ratio 

 of-87:l. 



Comparing. this plate with that in experiment VIII., it will be seen that 

 the power of resistance of the former is more than one-fifth greater than that 

 of the latter, showing that there must have been some defect in the longer 

 section of the specimen, or fracture would not have ensued at so early a 

 period of the experiment. We cannot abandon this experiment, as no defect 

 presented itself, if we except the highly crystallized state of the fracture, 

 both specimens having been drawn asunder in the direction of the fibre. In 

 these experiments it will be observed that the infusion of heat into wrought- 

 iron plates, from zero to 212°, does not injure, but rather improves, their 

 tensile strength. 



Table XI.»— Strain applied in the direction of the fibre. 

 Boiler plate; sectional area =2*01 X •32=*64'32 sq. inch. 



From this experiment it appears that an increase of 58° of heat makes no 

 perceptible difference in the strength of the plate. If we take the mean of 

 the two previous experiments, in the direction of the fibre, it will be found 

 there is no great difference between them, the mean of Tables VIII. and X. 

 being iijTOS, and Table XI. giving 44',020 lbs. to the square inch. 



I 



