Siemens Mercury Unit of Electrical Resistance. 

 If a m is the mth, a n the nth arc, the damping- ratio is 



349 



K: 



© 



and X = log nat. k. 



em. 



a n . 



\a. 



lb. 



II. 



III. 



302-81 

 288-48 

 255-81 

 313-27 

 298-16 

 283-29 

 268-72 

 388-10 

 37014 

 352-90 

 336-47 

 336-82 

 318-93 

 301-73 



20 

 29 

 32 

 20 

 24 

 28 

 32 

 20 

 24 

 28 

 32 

 15 

 19 

 23 



247- 17 

 222 30 

 21430 

 25114 

 238-15 

 225-64 

 214 02 

 316 94 

 302 18 

 287-80 

 27439 

 285-50 

 269-87 

 255 04 



k. 



101201 

 101192 

 1-01189 

 1-01309 

 101331 

 101347 

 1-01348 

 101199 

 1-01200 

 101207 

 101207 

 1-01387 

 1-01402 

 101411 



Mean. 



k = 



101194 

 001187 



101334 

 001325 



: 101 203 

 01196 



101400 

 = 0-01390 



Recoil-observations. — The distance of the scale from the coated 



mirror amounted to 4050*6 millims., of which 5*6 millims. were 



represented by glass plates. The refractive index being taken 



5*6 

 equal to V5, we must deduct from the above number -q~= 1'9 



millim. to compensate for the refraction of the rays of light. 

 Thus, then, r = 4048 . 7 m iin ms . 



An amplitude of vibration a measured on the scale signifies on 

 a circle of the radius unity the arc A*, 



A= 



8097-4 



V 38097 V 



a-0 000000005 la 2 

 8097*4 



During the recoils the bifilar magnetometer was observed, and 

 from the graphical representations of the readings the position 

 8 (page 343) deduced for the time of each induction-shock. 



I will give the set of observations la. in a complete form. 

 s i> s & s 3> s 4 are t ^ e points of reversal observed on the scale ; the 

 induction-shocks lie before Sjand^. Behind the thick vertical line 

 the large arc a = s 3 —s L and the smaller arc 6 = s 2 — s 4 are given, 

 in all cases the mean of two adjacent differences. The horizontal 

 line indicates the distinctly marked constancy of the vibrations. 

 This always occurred soon, as the starting-point was the initial 

 position of the inductor, always defined by preliminary experi- 

 ments, in which the first deflection had at once almost the ulti- 

 mate constant value. 



* If we took into account that a third of the moment of rotation is not 

 proportional to the angle but to its sine, we should have to put fifg instead 



of 



'he difference is vanishingly small. 



