XII. The same experiment was repeated with the coil on stand being placed farther from the central coil. The sparks were about 20 feet long in a straight line. Fifty throws of the switch were used as before. The procedure was slightly modified by setting off about 1/3 of an Eastman flash powder to bring out my features.
XIII.XIV. } In these two plates the effect was improved by making the streamers issue symmetrically from ball 8" diam. with two wires on each side: >0<. Fifty throws of the switch were used and the procedure was as in XII. In all the later instances described the plates and other particulars were the same as before.
Note: open lens, arc light 5 min.
Note: to preceding description of photographs taken with Mr. Alley:
As before stated, in most cases when the ânew extra coilâ was shown in action, the vibration of the system including it was about the normal, only slightly modified by the attachment of terminals of comparatively very small capacity. The âextra coilâ system was namely adjusted to the vibration of the primary system which took place with one primary turn (the two primary cables being in multiple) with all the jars being connected in two sets in series and with the regulating coil all but 1/2 turn out. Under these conditions the secondary was very strongly reacting upon the primary modifying the inductance of the latter so that the inductance of the primary turn instead of being as previously determined about 57,000 cm was diminished to 41,000 cm approx. Now the inductance of the connections to the condensers, and 1/2 of one turn of regulating coil, was as will be seen with reference to the table, often referred to - nearly 6000 cm. So that the total inductance of the primary circuit under these conditions, was owing to the resonating secondary, was only 41,000 + 6000 = 47,000 cm, or $! {47 \over 10^{6}} $! henry. Now the capacity in the primary was two sets of eight tanks in series or four tanks total, that is, 4 x 36 = 144 bottles or 144 x 0.009 = 0.1296 mfd, approx. Hence the period was
Tp = $! {{2 \pi \over 10^{3}} \sqrt{0.1296 \times {47 \over 10^{6}}}} $! = $! {{2 \pi \over 10^{6}} \sqrt{6.0912}} $! = $! {{2 \pi \over 10^{6}} \times 2.47} $! = $! {15.512 \over 10^{6}} $!
or n = 64,466 per sec. or nearly so. This is a considerably quicker vibration than when the secondary is not active. As the âextra coilâ did not have sufficient inductance in itself, another coil was inserted in series with the same to insure the resonating condition with the above primary vibration. This latter coil was wound with wire No. 6 on an old drum 2 feet diam. and 6 feet long. Particulars about this coil will be recorded on another page.
22*
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