Results Achieved

With smaller toroid, spark gap Type A:

10-15 streamers max. 20" long breaking into air
Discharge to a grounded rod max. 20" long

Discharge into air, to a grounded rod and through a fluorescent tube. About 7 s. exposure time, 200 ASA
(actually shot in complete darkness)

With bigger toroid, spark gap Type A:

3-6 streamers max. 31" long breaking into air
Discharge to a grounded rod max. 24" long

Discharge through a wood stick: the stick glows orange from inside (sorry, you hardly can see that from the picture).
Picture by courtesy of Mika Salkola

The following pictures were taken with a videocamera by Mika Salkola and then grabbed by me. The quality is... well, judge by yourself.

CLICK ON THE IMAGES FOR A LARGER VIEW

Streamer into air Streamer into air Streamer to ground Discharge through a fluorescent tube Streamer to strike rail Wood stick glowing orange Streamer into air Double streamer into air

With bigger toroid, spark gap Type B:

3-6 streamers max. 40" long breaking into air
Discharge to a grounded rod max. 31" long

The spark gap gets sensibly warm (3 gaps). Using 4 gaps, streamers to a grounded rod are a little bit shorter but the spark gap stays cold

"Banjo" streamers into air

Streamers into air and to grounded rod

With bigger toroid, Rotary Spark Gap (RSG):

3-6 streamers at least 40" long breaking into air
Discharge to a grounded rod max. 31" long

The RSG stays cool and the breaks make a constant tone, sign of a stable break rate. Streamers are longer than with other configurations and their shape is usually different: they are like real "trees" with many biforcation.

Nice effects by varying the RSG rotation speed: there are several spots where interference is generated at a very low frequency (1 - 3 Hz). It is possible to ear the coil "pulsing" or "breathing" and the streamers getting longer and shorter at a few Hertz frequency.