374 Hydrogen Gas. 
6. Leyden Jar. When water has been quickly frazen 
in a Leyden bottle, the outside coating of which is not 
insulated, the bottle receives a weak electric charge ; 3 the 
outside becomes negative and the inside positive. If the 
water be quickly thawed, the electric action is reversed, 
the inside becomes negative and the putetie positive. 
Grothus. 
7 Chemical effects of Magnetism. According to profes- 
sors Hanstein and Maselsmann this effect may be shewn 
as follows. Bend a glass tube intoa syphon, and place in 
the angle a portion of mercury not sufficient to close the 
connection between the two legs ; then introduce a solu- 
tion of nitrate of silver until it rises in both branches. 
Then place the branches of the syphon in the magnetic 
meridian and the Arbor Diane will form much more ra- 
pidly and in more perfect crystals, than if the branches be 
placed in the direction of east and west. ‘The crystalliza- 
tion is in the first case most perfect in the northern branch. 
If while the syphon is in a plane perpendicular to the 
meridian, an artificial magnet be brought near it, the silver 
will be deposited more abundantly, and in this case the 
south branch is more active than the north. 
Murray has made an experiment analogous to this By 
putting an iron rod into very dilute nitrate of silver. If 
the rod be not magnetized the silver is not reduced, but as 
soon as a magnet is brought to touch it, the reduction takes 
place. A magnet covered with varnish will equally effect 
the reduction, but in this case he finds, in opposition to 
Hanstein and Masselsmann that the strongest action is at 
the north pole. Ludecke has observed that when a glass 
vessel, filled with a concentrated saline solution (e. g. 
acetate of lead, or muriate of ammonia, or sulphate of 
protoxide of con) is placed on a horse-shoe magnet ,it wil! 
be found, in the course of a few hours, that the crystals 
will form between the two poles a well marked circular 
spot, which, by the more intense magnetic force in that 
region is deprived of crystals, while they are thickly de- 
posited all around. Idem. 
8. When Hydrogen £4s, (obtained from iron filings pe 
dilute sulphuric acid,) is passed through pure alcohol, the 
