L89L] 



Young's Modulus for Crystals, 

 beryl. 



397 



Diagram (8). t = 0'0415 inch 



b = 0-0877 

 W = 0-1381 Ib. 



Diagram (9). t 0-0292 inch 



I - 0-1065 

 W = 0-0217 Ib. 



fluor. 



In diagram (9) the abscissa is plotted to a different scale, since, 

 swing to the extreme brittleness of fluor spar, a displacement of only 



aut 1'5 of the ordinary division of the scale could be safely use 

 rhen the thickness of the specimen was about 0'03 inch, and many 



ims of this substance were broken in attempting to produce greater 

 sxures. 



In this experiment the greatest departure of the centre of the 

 3am from its unstrained position is about O'OOOOl inch. 



Diagram (10) shows some of the properties of zinc. The curves 



lumbered 1 to 8 are really one continuous experiment. A light 



reight was allowed to act on a beam of sheet zinc, and the deflections 



lused by it were noted every thirty seconds for ten minutes. These 



leflections are shown by the first part of curve 1. The weight was 



len removed, and the recovery of the beam was observed for five 



linutes. This forms the second part of curve 1. 



The experiment was then repeated with the same weight, and the 



suits are shown in curve 2. Additional weight being applied, the 

 line course of procedure gave curves 3 and 4, and in like manner by 

 till further additions of load curves 5, 6 and 7, 8 were obtained. 



The dimensions of the beam were : 



t = 0-0373 inch 

 6 = 1558 



For curves, 1, 2 

 8, 4 

 5, 6 



7 8 

 <> o 



weight = 0-4026 Ibs. 

 =0-8052 

 = 1-657 

 = 2-110 



Diagram (11) gives (a) the permanent set, (&) the immediate 

 stic deflection, (c) the deflection at the end of ten minutes. These 

 taken from diagram (10). 



