Mr. Ben net’s Defer ipt ion, &c. 289 
ge*r of it in a thunder-florin. I therefore contrived the fol- 
lowing doubler for the purpofe of more eafily making an 
eleCtrico-meteorological diary, which I undertook at the requeft 
of my friend Dr. Darwin, who hoped, that from thence fome 
lights might be thrown on tiie caufes of the fudden changes of 
aerial currents, a circumftance of fo much importance to the 
early growth and maturity of vegetation. 
I place upon my electrometer, deferibed in a former Part 
of the Philofophical Tran faCtions, a circular brafs plate, three 
or four inches in diameter, polifhed and thinly varnifhed on 
the upper furface. On this I place another brafs plate, of 
equal diameter, polifhed and varnifhed on both Tides, with an 
infulating handle attached to one edge of it. A third plate is 
alfo provided, of equal diameter, polifhed and varnifhed on the 
under Tide, and with a perpendicular infulating handle from the 
center of the upper Tide, fimilar to thofe mentioned in the 
Appendix to my laft Paper. 
The method of collecting eleCtricity from the atmofphere, 
and continually doubling it as much as required, is as follows. 
It the weather be dry, I carry into the open air a lighted torch, 
not liable to be eafily blown out, or a fmall lantern with a 
lighted candle in it, to the bottom of which is fixed, by means 
of a Tocket, an infulating handle of glafs covered with fealing- 
wax ; in the other hand is carried a coated phial : then, ele- 
vating the flame a little higher than my head, I apply to it 
the knob of the phial, holding it in this lituation about half a 
minute. Then returning into the houfe (where the above 
deferibed doubler is kept dry, by being placed on a table not 
far from the fire), I apply the knob of the phial to the under 
fide of the firfl: plate, which lies immediately upon the electro- 
meter, and at the fame time touching the fecond plate with a 
finger of the other hand. Then laying afide the phial, I lift up 
the 
