“ee 
; : * 
44 
4h 
—_ 
great body of experimental evidence and with present 
theory. | 
202 J. A. POLLOCK. 
Drude (loc. cit., p. 330) gives the measures of the wave 
lengths of the vibrations connected with four open circles, 
three of them being supported by wooden cores and one 
being wholly surrounded by air. For the latter the half 
wave length was 259 cms. when the length of the wire was 
243 cms., the ratio being 1°065. Drude concludes from this 
experiment that “the half natural wave length of a nearly 
closed thin wire circle is 6°5‘+ greater than its length.” This 
value I believe to be far too small. 
With the circuits used, the present experiments give for 
the ratio of the perimeters of rectangles, 30 cms. in width, 
to the lengths of open circular circuits when both have the 
same period of vibration, values varying from 2°38 for a 
rectangle with a perimeter of 760 cms., to 2°28 for one 
whose perimeter is 1050 cms., the gaps in the circles being 
about 15 cms. long to avoid any appreciable capacity effect 
due to the proximity of the ends of the circuit. 
Comparing this result with that given just above for 
straight wires, itis found that the electrical vibration con- 
nected with a wire bent into the form of a circle, with a 
considerable gap in its circumference, has a shorter period 
than that associated with a straight wire of the same length. 
The actual result obtained is that a copper wire 0°33 cms. 
in diameter, if bent into the form of a circular arc, with 
its ends separated by a distance of about 15 cms., requires 
to be 3°2% longer than a straight wire of the same gauge 
310 cms. long, to give a radiation of the same wave length, 
and 3°4% longer than a straight wire 445 cms. long. This 
result is to be expected,’ when the ends of the circular are 
are not brought too closely together, as the inductance of 
1 See Thomson—“ Recent Researches,” § 385. | 
