PHYSICS: C. BARUS 
339 
The most direct criterion as to changes of phase is the rotation of 
ellipses as indicated in figure 8. I shall give a few examples of what 
is observed in the telephone displacement in question. 
In the absence of current the fringe bands were nearly horizontal 
parallel lines. The secondary was closed with 5000 ohms and the 
inductance of the three telephones. From the position b (ellipse 1, 
figure 8 quiescent) the inductor telephone was quickly displaced to 
position c. The enormously eccentric, finally linear ellipse, 2, follows, 
which then rotates and contracts counterclockwise through the figures 
3 and 4 into the sharp bands (usually but not always) no. 5. These 
dupHcations then separate on further rotation into the final quiescent 
form, 7. The arrows indicate the drift of one of the four points of 
tangency. On returning from c, by quickly sliding the telephone 
inductor into the position b, the figures roll clockwise from 7' to 1'. 
Number 7' passes at once through the highly eccentric ellipse 6', 
though in other slower adjustments intermediate sharp duplicates like 
5 may be detected between 6' and 7\ The stretched ellipses, which 
follow immediately after the change of aspect of the telephone bobbin 
to the magnetic lines, are noteworthy. They result from the sudden 
reversal of the magnetic field in spite of the vibration. Ellipses cross 
over or change sign of rotation at 2 and 6', but not near 3' or between 
5, the latter being oscillations. The corresponding cases for capacity, 
were similar on the whole, though less pronounced. Moreover the first 
and final forms were not quite in opposed phases. 
10. Narrow bifilar. — After obtaining the favorable results just de- 
scribed, it seemed obvious that the sensitiveness could be further in- 
creased by diminishing the distance between the bifilar wires. Accord- 
ingly, with the same inductor, figure 4, the above wires (diameter 
0.023 cm.) were adjusted at but 1.5 cm. apart by decreasing the diame- 
ter of the lower pulley. A few other modifications were added. The 
results however were disappointing throughout. 
A final observation may be added. The auxiliary audible telephone 
responded with about equal loudness when the telephone circuit was 
closed with 400 ohms and when a condenser of 1 microfarad capacity 
was inserted. But the vibrator reacted in the former case (resistance 
and selfinduction) with a deflection of 23 scale-parts, whereas in the 
latter (capacity) the response was at most 2 scale-parts; and this re- 
quired a slightly different tension of wire. The metallically closed 
circuit therefore affected the vibrator at least 12 times more strongly 
than the oscillation due to the capacity of 1 microfarad. Small capaci- 
