Nikola Tesla Books
Books written by or about Nikola Tesla
the few trials which were cut short because of the danger threatening from the sparks, the lightning arresters were observed but no spark was noted. In the forenoon the mains were tested and it was found that one of them was fairly grounded which to some extent also made the other defective. This probably was the reason why the sparks no longer appeared on the arresters.
A number of curious observations were made during the trials with the elevated ball. A fly was seen to light on the top of the ball and when the switch was thrown in the insect disappeared evidently thrown off with great force. Another such insect alighted on the under part of the ball, and the current being thrown in just about at the moment when the fly started off, the fly was seen to fall from a distance of about one foot from the ball straight down to the floor, evidently killed in the flight. Still more curious it was to see a moth at a distance of fully eleven feet from ball, near to the wooden frame fall straight down as the switch was thrown in. The strongly electrified ball evidently exercises a strong attraction on a small insect which is drawn towards it every time the ball is electrified. This was repeatedly tried.
An observation less amusing but more useful was that when the ball with its circuit were well tuned and no streamers appeared, owing to good insulation of leading cable - there was a decided tendency to break the jars in the primary. Evidently, when there are no streamers the vibration is effected with lesser loss and hence there is a great rise of e.m.f. reacting upon the primary. This at least appears the most plausible reason for the phenomenon observed.
Light seems to interfere decidedly with the streamers from ball and wire and it is also unmistakably noted that the noise of the discharge is lessened when the sunlight falls upon the apparatus.
Spark gaps were established in a number of ways as by connecting both coil and secondary to ground and each to one of the balls and establishing a spark gap between the latter.
Finally the ball was again connected as before and elevated, a point being first placed on top to facilitate formation of streamers. It was curious to observe that the streamers were carried away horizontally, and eventually blown out by the wind. The resonating action was strong but the length of the streamers could not be estimated. From the leading cable the discharge would sometimes leap to a distance of at least 10 feet. The action of the wind suggests the idea of preventing the formation of wasteful streamers by a current of air.
168
August 31
Again he works with the oscillator, "additional coil" and capacitive loading in an old layout. The aerial with the sphere was going through the opening of the roof of the laboratory (refer to laboratory photographs). Due to the humidity he performed short tests. In a few cases he checked the lightning protector, but there were no sparks on it. The test of the supply line indicated that one supply line has a good connection with ground. It is assumed that he finally found the cause of the nonexistence of sparks on the lightning protector.
During the experiments he observed that small insects are killed when they are within the strong electro-magnetic field of the oscillator.
When current streamers are non-existent, the tendency of capacitor flashover in the primary circuit appeared. The explanation is simple: the current lines represent the secondary load and when they don't exist, voltages in both oscillator circuits rise.
