There has recently been a little discussion in these pages on the subject
of lightning, some having stated that they discerned the discharge to take
place upward--that is, from the earth toward the cloud. I will not venture
so far as to say whether or not the direction of the discharge is
discernible; possibly the flash may sometimes be long enough to enable one
to tell; but I have never so seen it, and have always looked upon the eye
as a deceitful member--very. "The lightning flash itself never lasts more
than 1/100000 of a second." It is, however, just as likely that a
discharge may travel upward as downward. What controls the discharge? Does
the quality of the charge?--that is to say, is the positive or the
negative more prone to break disruptively through the insulating medium?
Investigations with Geissler's and other tubes containing highly rarefied
gases have made it tolerably clear that there is a greater "tearing away"
influence at the negative than at the positive pole, and if two equal
balls, containing one a positive and the other a negative charge, be
equally heated, the negative is more readily dissipated than the positive.
But, so far as we at present know, this question enters into the
discussion scarcely, if at all.
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