Manchester Memoirs, Vol. xliii. (1899), No. 10. 9 



justifiable the specific gravity of a length of unstrained 

 wire was determined. This was found to be 8*9 18. 

 Coincidently a length of wire was tested with a load of 

 30lbs. and annealed, this being repeated three times. Its 

 specific gravity was then found to be 8*905, the alteration 

 in stress due to this would be '14 %. Returning to the 

 wires, it will be noticed that in the first test plotted there 

 are irregularities in the elastic portion, and further that 

 the yield-point is not definite, as the elastic portion begins 

 to curve away, and finally settles down into a straight 

 line inclined to the axis at an angle whose tangent 

 is '273. The elastic limit is reached soon after the eighth 

 point on the curve, and the yield-stress is certainly not 

 lower than i"22 tons per square inch. 



After annealing, stretching, and re-annealing, the wire 

 was again tested. The irregularities previously observed 

 in the elastic portion of the curve were still repeated 

 though in a less degree, as can be seen from the 

 diagrams. The final value oi n has risen to '423, and the 

 elastic limit though still slightly indefinite has been taken 

 to occur at the seventh point on the curve. This corres- 

 ponds to a yield-stress of i"ii tons per square inch. 



The wire was now annealed and retested. It will 

 now be noticed that the irregularities in the elastic 

 part have disappeared, and that the points form two 

 straight lines. The value of n is •413, and the elastic 

 limit, which is now quite definite, is at the fourth point, cor- 

 responding to a yield-stress of 715 tons per square inch. 



Unfortunately the test of this wire was carried no 

 further, but the lowering of the yield-stress and the 

 gradual smoothing out of the curve are characteristics 

 which appeared in the wires tested previously to this. 



Thus, as far as the experiments were carried, repeated 

 annealing and straining besides rendering the wire more 



