58 



DISPLACEMENT INTERFEROMETRY BY 



TABLE 2. Modulus of hard rubber. End-thrust apparatus with sheathed rods; ., = 2.45 

 cm.; 2r=o.36y cm.; .4=o.io6 cm. 2 ; 1=45; 2^ = 10.3 cm.; 2R'=j.o cm. Permanent 

 load I kg. each. Achromatic fringes. 



* Slight adjustment. ** After adjustment for larger fringes, 

 t Next day. J Two days later. 



*** 2 hours later. 



6 and 7 a special collection of data was investigated two days later at the 

 highest loads which the apparatus admitted, 4 to 5 kg. These are shown after 

 d (fig. 35) and with a further lapse of time after e. It is interesting to note 

 that whereas the contractions under 5 kg. are relatively stationary, the con- 

 tractions at 4 kg. increase in the successive loadings and hence E also in- 

 creases. Otherwise the behavior, allowing for the fact that the rod had been 

 stressed for several days, is about the same, cast, par., as before. 



In figures 37 and 38 results 1 with special reference to hysteresis are shown 

 as a whole, indicating the three successive loops terminating at r, s, t, for 

 loads between i and 3, i and 4, and i and 5 kg. on the 0.106 sq. cm. of section. 

 It is difficult to interpret the individual data, because clearly their nature is 



1 As the data are sufficiently reproduced by the curves, the numerical tables have been 

 removed. 



