on the Flexihility and Strength of Stones. 



291 



The first trial, that with the 30-inch distance, will give the 

 most accurate measure of the elastic force ; but it is not a fair mea- 

 sure of the cohesive force, because it was evidently broke by the 

 momentum, the weight acquired by the addition of the last 10 lbs. 

 The 14-inch length bore the weight some time before it broke. 



The specific gravity was found to be 2*706 j and it absorbs 

 TTns of ''^s weight of water. 



1 observed that the fractures bore a close resemblance to one 

 another, and found that the plane of fracture made always nearly 

 the same angle with the axis of the piece. This angle is about 

 83°. I have not observed a similar regularity in any other kind 

 of stone, and it is either a remarkable coincidence, or the eflfect 

 of the structure of this kind. 



2. There is some difference in the quality of the Portland 

 stone used in London ; the best and strongest kind is of a browner 

 colour than the others. The specimen with which our experi- 

 ment was made was of the brown variety, and of a regular tex- 

 ture, without apparent defect. The length between the supports 

 was 24 inches, the breadth 2 inch, and the depth 1'45 inch. 



Weight 



10 lbs. 

 20 — 

 30 — 

 40 — 

 50 — 



m — 

 70 — 

 80 — 

 90 — 

 100 — 



D 



epression 



Oo2 



•01 inch. 

 •015 ■ _ 

 •02 ^ 

 •022 — 

 •025 — 

 •0275 — 

 •03 — 

 •032 — 

 •035 — 

 •037 and broke. 



Thi 



