352 Abstract of Mr. Faraday’s Experiments on tne 
with the other, and then lift this disk from the zinc. As 
soon as the separation is effected, the gold leaf will strike ~ 
the ball, usually, if the one be not more than 3, of an 
inch, apart from the other. Ten contacts of the same disks, 
of copper and zinc, will be found necessary to produce a 
sensible divergency in the leaves of the Condensing Elec- 
trometer. That the phenomenon arises from the dissimi- 
larity of the metals, is easily shewn, by repeating the ex- 
periment with a zinc disk, in lieu of a disk ofc The 
separation of the homogeneous disks, will not be found to 
produce any contact, between the leaf and ball. I believe 
e has been heretofore contrived, by which the elec- 
trical excitement resulting from the contact of heteroge- 
neous metals, may be detected by an Electroscope, without 
the aid ofa condenser. It is probable, that the sensibility 
of this instrument, is dependent on that property of elec- 
tricity, which causes any surcharge of it, which may be cre- 
ated in a conducting surface, to seék an exit at the most 
projecting termination, or point, connected with the sur- 
face. This disposition is no doubt rendered greater, by 
the proximity of the ball, which increases the capacity of 
the gold leaf to receive the surcharge, in the same manner, 
as the uninsulated disk, of a condenser influences the elec- 
trical capacity of the insulated disk, in its neighbourhood. 
It must not be expected, that the phenomenon above de- 
scribed, can be produced in weather unfavourable to elec: 
tricity. Under favourable circumstances, I have produce 
it, by means of a smaller Electrometer, of which the disks 
are only 2} inches in diameter. The construction, 48 
respects the leaf, and the ball, regulated by the microme- 
ter screw, remaining the same; the cap of a Condensing 
Secon, and its disks, may be substituted for the zin¢ 
18 e 
ee ec 
Arr. XXI.— Abstract of Mr. Faraday’s Experiments 0% 
the Condensation of Several Gases into Liquids. Ed- 
inb. Philos. Journ. No. XVIII. 
Tus very valuable and interesting paper, which will ap- 
pear in the second fer of the Philosophical Transactions 
for 1822, contains Mr Faraday’s Experiments on Sulphu- . 
rous cid, Sulphuretted Hydrogen, Carbonic Acid, Ev 
