TENSILE STRENGTH OP RIVET IRON. 

 Table XXVII Sectional area =-19635. 



419 



The above bar, although of the same quality and appearance as that in the 

 previous experiment, gives no less than 6952 lbs., upwards of three tons, 

 greater tenacity than its predecessor. The former appeared equally tough 

 and fibrous in the fracture, and the elongation in the same distance was 

 rather mor^ than in the latter, and yet it is about one-twelfth weaker. 



Table XXVIIL— Sectional area =-24850. 



81,830 



=36-531 tons. 



In this experiment there is a decrease in the strength with an increase of 

 temperature of 90°, but in the next experiment, with a further increase of 

 20°, the strength again rises from 81,830 to 86,056, or nearly two tons, 

 which shows that the increase of 100° of temperature has not seriously 

 affected the molecular constitution of the iron. This irregularity, after so 

 constant an increase of strength, indicates that we have about reached the 

 maximum strength of the material. We shall see hereafter that the increase 

 of strength from —30° to 325° has been four-tenths, nearly one-half. 



Table XXIX. — Sectional area =-24-850. 



The difference between this and the last experiment is about one-eighteenth 

 part of the former in favour of the latter. This difference we cannot account 

 for by an examination of the fractures; but taking the mean of the two, and 

 comparing it with Table XXVIL, it appears that we have passed the maxi- 

 mum strength, and recede from it in the ratio of 87,522 : 83,94'3, or as 1 : '959. 



2e2 



