PHYSICS: C. BARUS 
337 
8. Selfinduction in the Primary, — The present experiments contain an 
element of uncertainty owing to the mechanical (or possibly magnetic) 
coupling of the vibrator cc' , on the interferometer, figure 2, and the 
objective of the vibration telescope V. I have not thus far been able 
to eliminate this. Information was sought by inserting additional self- 
induction into the primary. The two small electromagnets, figure 2, 
e", (about an inch long), which could be used either separately or in 
series, were available for this purpose. 
The different elements of harmonic motion involved in the experi- 
ment may be analyzed as follows. The whole is fundamentally sub- 
ject to the vibration period of the spring at the interruptor of the 
primary, which gives the impressed electromotive force 
Z = /o sin co/ (1) 
The current induced in the primary controls the objective of the vibra- 
tion telescope, which thus moves with a lag a subject to 
i = io sin (oit- a) (2) 
and this may be modified by the resistance and inductance in the 
primary. 
The objective is as stated either mechanically or magnetically coupled 
with the vibrator on the interferometer in a way yet to be ascertained; 
for each has an independent mounting. Hence the vibrator displace- 
ments s are subject to an equation with a lag or lead 
s = So sin (w/ - jS) (3) 
in the absence of current in the secondary {R = co). 
Finally the secondary, if carrying current has its own lag or lead y 
depending on the R, L, C there inserted, and is thus subject to an equation 
s = So sin (ojt — y) (4) 
where y is essentially associated with jS, as seen in the preceding 
paragraphs. ^ 
If we suppose the coupling implied in equation (3) to be uniform, 
the lag in equation (2) may be made obvious. 
In these experiments the vibration figures were very large and very 
definite in the successions of their changes with L, however frequently 
repeated; but unfortunately the induction in the secondary is soon 
quenched. 
P. Direct Telephonic Induction. — The influence of the oscillating mag- 
netic field on the telephone is much more pervasive than one is apt to 
