[Spridgets] Extra sparks

[Andy Webster]

Hi everybody,
I started my engine last night, to put the timing light on, and use the colortune glass spark plug to tweak the mixture.
In the dark I noticed  sparks around the base of the distributor. 
I could clearly see sparks near the bolts which hold the mounting clamp to the engine block.
Is this indicative of a short circuit perhaps or a bad earth of the distributor?
Engine ran OK, occasional miss and I think it still needs some adjustment to get everything optimised. 
Anyone got any ideas why I'm seeing sparks externally?
(Points distributor, Aldon yellow, based on 45d unit)
Cheers
Andy