A spectacular conclusion of one of the popular electric exhibitions of the time was likely to be the electrification of a boy suspended by many silk threads from the rafters; his hair stood on end and sparks could be drawn from the tip of his nose.
Does the sentence mean the most spectacular conclusion was in fact that of the electrification of the boy, or that the electrification of the boy was among the likeliest conclusions to happen at that time and it could have happened or not ?