354 MR CADELL ON EXPERIMENTAL RESEARCHES IN MOUNTAIN BUILDING. 



A band of the most elastic quality of india-rubber, 7 inches broad and a quarter of an 

 inch thick, was grasped at the ends between vertical pieces of wood bolted together. The 

 left end of the band was fixed to the sole of the box in which former experiments were 

 arranged. The pair of bolts on the right projected through the wood, and passed through 

 an iron plate fixed about an inch from the outer face of the block, as shown in the figures. 

 In the centre of the plate, between the bolts, a hole was drilled large enough to admit the 

 free end of the screw-shaft. This end of the shaft was fitted with a collar, which worked 

 against the inside face of the plate, and prevented the shaft being drawn through, but 

 permitted of its free rotation in the hole. The other end of the screw remained in its old 

 bearings attached to the sides and bottom of the box. By turning the screw in a left- 

 handed direction the elastic band could thus be stretched through any desired distance. 



The part .of the elastic band measuring 2 feet between the blocks was stretched to ;t 

 length of 3 feet. In Favee's experiments the sheet of caoutchouc was extended in the 

 same proportion. A layer of very tenacious clay was then plastered over the roughish 

 surface of the elastic band and covered with a sheet of brown paper. A second and 

 thicker clay bed of a "shorter" and stronger consistency w T as lastly laid over the 

 paper. The depth of the whole section was about 1-g inch. 



• On slacking the screw and allowing the elastic band to contract to its original lenoth, 

 the upper bed of clay above the brown paper was observed to swell up into little waves, 

 just as the surface of the clay in Favre's experiments was observed to do. These are 

 well shown in fig. 23. 



Pie. 24. 



