396 t^'oreiiin Jjiterature and Science. 



tf this ring have a (jiameler of three or four inches, and 

 the instrument be not too heavy, it possesses the power oi" 

 self direction, always arranging itself in a plane perpendic- 

 tilar lo the magnetic meridian. Bib. Univ. 



4 ] . TiOo other ingenious and simple instruments for shelving 

 ihe effect of Electrn-magnelism, are described in the recent 

 journals. One* of these, by P. Barlow, Esq. of the Royal 

 Military Academy, is as follows: — 



"A B (see the plate at the end) is a rectangular piece of 

 liard wood; C D E a stout piece of brass or copper wire 

 and n b c d, a rectangle of smaller copper com, (sol- 

 dered at E) on the lower side of which the wheel W of thin 

 copper turns freely:/^ is a small reservoir of mercury 

 sunk in the wood; t g i ^ narrow channel running into it. 

 H M is a strotjg horse shoe magnet> 



"Mercury being now poured into the reservoir/ ^ till 

 the teeth of (lie wheel are slightly immersed in it, and the 

 surface covered v.'ith weak diluted nitric acid, make the 

 iconnection with the battery at i and D: and the wheel W 

 will immediately begin to rotate with an astonishing velocity, 

 far beyond the power of the eye to follow, and will thus 

 produce the most pleasing effect." 



'"The galvanic apparatus which \ employed to produce 

 ;this motion was the Calorimotor of Dr. Hare which I had 

 mad€ of the plates of my old battery, 20 of zinc and 20 

 of copper, each ten inches square. But a much less pow- 

 erful combination will be sufficient," 



The suspension of the wheel is shewn in figure 2, and 

 it rnay be proper to add, that in order to ensure a complete 

 contact, the two sockets, or the end of the spindle, should 

 he amalgamated, as also the tops of the points of the wheel. 



'* If the contact be changed, or if the magnet be reversed, 

 the motion of the wheel will be reversed also : but I find 

 Ihc best effect produced v/hen the wheel turns inward. 



42. An Iron Steam Boat has recently made a voyage 

 from London to Rouen in 55 hours, and then proceeded to 

 Paris. This is doubtless the first attempt to traverse the 

 ocean in a vessel composed of any material but wood, 



*■ For the other, see Phil. Mag. for Jane. pa. 434, 



