352 Abstract oj Mr. Faraday^s Experiments on tne 



with the other, and then hft 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 y|^ of an 

 inch, apart from the other. Ten contacts of the san>e 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 of copper. The 

 separation of the homogeneous disks, will not be found to 

 produce any contact, between the leaf and ball. I believe 

 no mode has been heretofore contrived, by which the elec- 

 trical excitement resulting from the contact of heteroge- 

 neous metals, maybe detected by an Electroscope, without 

 the aid of a 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 seek an exit at the most 

 projecting termination, or point, connected with (he 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 produced 

 it, by means of a smaller Electrometer, of which the disks 

 are only 2^ inches in diameter. The construction, as 

 respects the leaf, and the ball, regulated by the microme- 

 ter screw, remaining the same ; the cap of a Condensing 

 Electrometer, and its disks, may be substituted for the zinc 

 disk. 



Art. XXI. — Abstract of Mr. Faraday^ Experiments on 

 the Condensation of Several Gases into Liquids. Ed- 

 inb. Philos. Journ. No. XVllL 



This very valuable and interesting paper, which will ap- 

 pear in the second part of the Philosophical Transactions 

 for 1822, contains Mr Faraday'? Experiments on Sulphu- 

 rous Acid, Sulphuretted Hydrogen, Carbonic Acid, Eu- 



