2S2 Analyses of Books. [Sept. 



** The temper was then lowered till the colour was an uniform 

 blue, or spring temper ; and the trials were repeated with the 

 same loads ; but the flexures were still the same. 



" It was now heated to redness and very slowly cooled. In 

 this state the same loads still produced the same flexures ; and 

 the load of 1 10 lbs. caused no permanent change of form. 



" The bar was hardened again, and made very hard ; in this 

 state the same loads produced the same flexures ; and 



lbs. inches. 



with a load of 300 the depression in the middle was 0*115 

 360 0-130 



580 broke. 



When the bar was relieved from the load of 350 lbs. it retained 

 a permanent flexure of 0*005 inches, which increased to 0*01 

 with the addition of.lO lbs. to the load. 



*' 1 found that a bar of much greater length might be tempered 

 without difficulty, and therefore had another bar made of the 

 same kind of steel; the length of which being 25 inches, about 

 double the flexure could be given with the same strain upon the 

 material, and therefore any small degree of difference in the 

 elastic force might be more easily detected, for the preceding 

 experiments are sufficient to show that if there be any dilference, 

 it must be extremely small. 



'' The breadth of this bar was 0*92 inches ; the depth 0*36 

 inches ; and the distance between the supports 24 inches. It 

 was soft, so as to yield easily to the file. 



•■ lbs. inches. 



^' With a load of 18*6 the depression in the middle was 0*05 

 37*0 0*10 



47*0 0*127 



The bar was then hardened, so that a file made no impression 

 on any part of it, and the same loads did not produce flexures 

 that were sensibly different from those in the soft state. 



" I then lowered the temper till it assumed an uniform straw 

 colour; when 



lbs. inches. 



with a load of 47 the depression in the middle was 0*127 



85 0*230 



130 0*350 



160 0*400 



The load of 160 lbs. produced a permanent set of 0*012, but 

 130 lbs. produced no sensible effect. The loading was conti- 

 nued, and 



lbs. inches. 



with 185 the depression in the middle was 0*50 

 385 1*04 



