492 



REPORT UN jNATIoNaL MU8EUxV1, 1886. 

 (rf) Limestone with a specific gravity of 2.72. 



See Am. Arch., November 4, 1882, 



(2) MODULUS OF ELASTICITY. 



By the term modulus of elasticity is understood the amount of force in 

 pounds requisite to stretch a bar of any material linch square to twice 

 its original length, provided the rate ot stretch could continue uniform 

 throughout the trial without the breaking of the material. The modulus 

 of rupture is the force requisite to break a similar bar 1 inch square 

 resting upon supports 1 inch apart, the load being applied in the mid- 

 dle. 



So far as the writer has been able to learn, but few tests of this nature 

 have been made upon stone. The following are from the report of Mr. 

 T. H. Johnson.* 



* Eep, State Geol. of Imiiaua, 1881, p. 45. 



