6 AKT. 9. S. KUSAKABE. 



10. From the amount of the deviations of the images, the 

 amount of bending due to each corresponding force is calculated, 

 by the following method. 



In Fig. 7, let the zero-reading be taken when the telescope 

 is in T while the mirrors Mj and Mg are in the position Mmj 

 and the mirrors M2 and M4 in the position M'm2. In reality, 

 the reflections of light by the mirrors take place, as a matter of 

 course, in the space of three dimensions ; but, for the sake of 

 simplicity, let us assume that the path of the ray of light lies 

 wholly on the plane of the paper. Let ab be the position of the 

 scale, and suppose that <x is a point which gives its images in the 

 field of the telescope after reflecting at s and s'. Suppose that, 

 after a certain number of operations, the specimen is bent, it is 

 rotated and also the telescope is displaced and rotated relatively 

 to the scale. Let their respective values be given by 

 a = angle through which the mirror M2 



is rotated as the specimen is bent, 

 — a=anlge through which the mirror Mi 



is rotated as the specimen is bent, 

 ^3=angle through which the specimen is rotated, 

 o=the component of the displacement of 



the telescope parallel to the scale. 

 Note that the other component is negligible relatively 

 to the distance between the scale and the telescope. 

 /'=the amount of rotation of the telescope. 

 Then, if 6 and co denote the angles between the mirrors M2 

 and M4, Ml and M3 respectively, we have 



