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 a constant and easy passage to the electricity of the clouds surcharged therewith, nothing, in my opinion, need be apprehended froin the apparatus electrifying the air; as its principal operation is conceived to be the reverse of that, viz. divesting the air of it's electricity. I am well apprized from experiments made here, that the earth is frequently electriﬁed plus, and the clouds minus; and that this change of plus and minus between the clouds and earth are sometimes seen to vary several times in a quarter of an hour: but in that case it is presumed, that the clouds, within the sphere of action of the apparatus, have by it's operation their electricity brought to the same standard with that of the earth in its neighbourhood, and vice versâ; and consequently, that the mischiefs which might arise from the difference of the densities of the electricity in the earth and clouds are prevented, by the equilibrium between them being maintained. This subject, in relation to the electricity’s being plus or minus, I many years ago consdered, and laid my thoughts thereupon before the public, as may be seen in the Philosophical Transactions, Vol. XLV.

That the atmosphere at times is very strongly electriﬁed, is evident, to say nothing of lightning, not only from our apparatus, but from the masts of ships, being beset with St. Elmo's fires, which I believe would scarce, if ever, happen, were the masts provided with an apparatus of this sort; unless the cause might be so great, and come on so fast, that the metal employed between the tops of the masts and the water might not, on account of the vastness of the cause, be large enough for the purpose. If it should so happen, St. Elmo's fires might still appear