[ 20 7 ] 
ing a constant and eafy paffage to the electricity of 
the clouds furcharged therewith, nothing, in my opi- 
nion, need be apprehended from the apparatus elec- 
trifying the air ; as its principal operation is conceiv- 
ed to be the reverfe of that, viz. diverting the air of 
it s electricity. I am well apprized from experiments 
made here, that the earth is frequently eledrified 
Pf us > an< 3 the clouds minus', and that this change of 
plus and minus between the clouds and earth are fome- 
times feen to vary feveral times in a quarter of an 
hour : but in that cafe it is prefumed, that the clouds, 
within the fphere of adion of the apparatus, have 
by it’s operation their ele&ricity brought to the fame 
rtandard with that of the earth in its neighbourhood, 
and vice verfd ; and confequently, that the mifchiefs 
which might arife from the difference of the dehfi- 
ties of the electricity in the earth and clouds are pre- 
vented, by the equilibrium between them being main- 
tained. This fubjedt, in relation to the electricity's be- 
ing plus or minus, I many years ago conhdered, and 
laid my thoughts thereupon before the public, as may 
be feen in the Philofophical Tranfadions, Vol. XLV. 
That the atmofpbere at times is very ftrongly elec- 
trified, is evident, to fay nothing of lightning, not 
only from our apparatus, but from the marts of fhips, 
being befet with St. Elmo's fires, which I believe 
would fcarce, if ever, happen, were the marts pro- 
vided with an apparatus of this fort j unlefs the caufe 
might be fo great, and come on fo fart, that the 
metal employed between the tops of the marts and 
the water might not, on account of the vaftnefs of 
the caufe, be large enough for the purpofe. If it 
fhould fo happen, St. Elmo's fres might rtill appear 
at- 
