KIXETIC MEASUREMENT OF THE ELASTICITY OF ROCKS. 







Elevation. 



ß = bench; jS,..=bridge ; J5^ = battery ; 7?=electro-magiiet ; 

 IZ'=hamnier ; il/=mirror; il/c- = microscope ; P=pully; 

 6i> = specimen ; »S'-. = stniig i.e. copper wire; <S'^=stan(l; 

 F=vice ; 11'= weight. 



A specimen Sp. clamped in the vice V is tapped by a hammer, 

 H, which is supported by a stand St. and maintained in constant 

 vibration electro-magnetically. A fine copper wire Sr. of ca. 

 0.05 mm. in radius is connected by means of bee's wax to the 

 upper end of the specimen and stretclied over a bridge Br. by a 

 tension due to the suspended weight, TK The copper wire, wliose 

 breaking tension is ca. 140 grams, is strained by a tension of 

 100 grams during some tens of minutes. Both the Ijritlge and 

 the microscope 3Ic. may sHde along an iron bench B of ca. 118 

 cm. in length, in which a scale is graduated for each mm. 



The distinction of forced and free vibrations is very impor- 

 tant, and must be clearly explained. If a vibration is the 

 response of the system to a force imposed upon it from without 



