4 AET. 9. S. KUSAKABE. 



force is exerted on the specimea, and that it is only the difference 

 of the weio'hts attached to the two strino-s which is effective in 

 bending it. That is to say, if m^ and m-i are the two weights 

 attached to the strings Si and S2 respectively, then their sum 

 ^1 + ^2 = ^1(1 regists the action of the bending force, tlie last of 

 which is due to their difference m2—')ni = ^l. For future reference, 

 Mo and M will be called the resisting 7nass and the effective mass 

 respectively. 



AVhen the effective mass is positive, the specimen is supported 

 by the fulcrums F3 and F4, and it becomes convex towards the 

 righthand side. In the other case, it becomes convex towards 

 the lefthand side, supported by the fulcrums Fj and F2. The 

 fulcrums standing face to face, i.e. Fj and F3 or Fo and F4, are 

 clamped so as not to push too tightly against the specimen, as 

 there is a possibility that the bending of the specimen will be 

 hindered by friction. 



A telescope, provided with a micrometer-screw, is rigidly 

 clamj^ed on a tripod. The scale, engraved on a ground-glass 

 plate, 20 em. long and 2 cm. wide is covered with a black board 

 having a slit, 8 mm. wide, and is illuminated by a row of small 

 gas jets. 



PROCESS OF OBSERVATION AND CALCULATION. 



The observation is generally as follows : — 



1. To begin with, equal weights, each i Mq, are hung on 

 the strings S^ and S2. 



2. A specimen is put between the fulcrums, passing through 

 the frame-work F, the last of which is to be clamped on the 



