Prof. Hare on the Combustion ofIro?i } fyc. 245 



sible divergency in the leaves of the condensing electrometer. 

 That the phenomenon arises from the dissimilarity of the 

 metals, is easily shown by repeating the experiment 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 here- 

 tofore contrived, by which the electrical excitement resulting 

 from the contact of heterogeneous metals maybe detected by 

 an electroscope without the aid of a condenser. It is pro- 

 bable, that the sensibility of this instrument is dependent on 

 that property of electricity which causes any surcharge of it, 

 which may be created in a conducting surface, to seek an exit 

 at the most projecting termination, or point, connected with 

 the surface. 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 electrical 

 capacity of the insulated disk in its neighbourhood. It must 

 not be expected, that the phenomenon above described can 

 be produced in weather unfavourable to electricity. Under 

 favourable circumstances, I have produced it by means of a 

 smaller electrometer, of which the disks are only 9.\ inches in 

 diameter*. 



The construction, as respects the leaf, and the ball, re- 

 gulated by the micrometer screw, remaining the same; the 

 cap of a condensing electrometer, and its disks, may be sub- 

 stituted for the zinc disk. 



On the Combustion of Iron by a Jet of Sulphur in Vapour. 



If a gun barrel be heated red hot at the but end, and a 

 piece of sulphur be thrown into it; on closing the mouth with 

 a cork, or blowing into it, a jet of ignited sulphurous vapour 

 will proceed from the touch-hole. Exposed to this, a bunch 

 of iron wire will burn, as if ignited in oxygen gas, and will 

 fall down in the form of fused globules in the state of proto- 

 sulphuret. Hydrate of potash, exposed to the jet, fuses into 

 a sulphnret of a fine red colour. 



An easy Mode of impregnating Water with Iron. 



If a few pieces of silver coin be alternated with pieces of 

 sheet iron, on placing the pile in water, it soon acquires a 

 chalybeate taste, and a yellowish hue, and in 24 hours flocks 

 of oxide of iron appear. Hence by replenishing with water 



* I think I have seen an effect from a disk only an inch in diameter, or 

 from a zinc disk having a copper socket to its handle. 



a vessel 



