294 On the Flexil/ilily and Strength of Stones, 



Table of the Properties of some Species of Stone. 



Kind of Stone. 



Statuary 

 marble 



Portland [ 

 stone . . I 



Long-annet 

 stone . . ■ 



Dundee stone 



Craigleith 1 

 . stone . . S 



Hailes quany "l 

 stone . .J 



Bath stone 



square 

 Inch. 



Weight of 



thcModulus 



of Elasticity 



of a square 



Inch. 



2,513,000 lbs. 

 1,910,000 — 

 1,800,000 — 

 1,152,000 — 



Height of 

 the Modu- 

 lus of 

 Elasticity 

 in Feet. 



569,000 



2,109,000 

 1,591,000 

 1,500,000 

 1,256,000 



593.000 





m'C 



.a .S a; 



a, li if « = 



2-706 

 2113 



2-212 



2-621 

 2-362 



2-155 

 1-975 



3: -a 



-rV) 



TTT 



In theory it is considered that bodies are perfectly homogeneous; 

 but in our trials we found that the magnitude of the facet of a 

 crystal, or the position of a scale of mica, produced a sensible 

 eftect on the result in a small specimen : therefore, to determine 

 the strength, the specimen should not exceed about 18 inches in 

 length, with a section of an inch and half square. When a spe- 

 cimen is long, it is not easy to add to the weight without giving 

 it a sensible degree of momentum. To determine the elastic 

 force, the specimen should be long in proportion to its depth, 

 and it is better when the breadth is not less than twice the depth; 

 then both the flexure, and the weight producing it, being greater, 

 the elastic force will be more correctly obtained. In short spe- 

 cimens there is a sensible degree of indentation at the supported 

 ends. 



I have observed, tnat of late stone-stairs, balconies, landings, 

 &c. are executed with a less and less quantity of material, and 

 that there is no prospect of a stop being put to this species of 

 misplaced ceconomy till some dreadful accident happens. What 

 a scene of horror the failure of a crowded balcony would create ! 

 a:id who can say what balcony may not be loaded to the utmost 



the 



