186 Messrs, Babbage and Herschel on the [Sept. 



the compass (by a more advantageous adjustment of the appa- 

 ratus) much nearer the revolving disc. The results were as 

 follows : 



Name of the re- 

 volving sub 

 stance. 



Copper 



Zinc 



Tin 



Lead 



Antimony 



Bismuth 



Mean of deviations 

 screwing and un- 

 screwing. 



280 54' 



26 42 



12 54 



7 



2 27 



32 



Ratio of force to 

 tliat of copper. 



1-00 

 0-93 

 0-46 

 0-25 

 0-09 

 0'02 



Agreeing as nearly as could possibly have been expected with 

 the foregoing. 



Of the other metals, silver appears to hold a high rank, and 

 gold a very low one in the scale of magnetic energy. Indeed 

 the latter metal rendered standard by copper was scarcely more 

 powerfully set in rotation than seemed fairly attributable to the 

 quantity of its alloy. 



The examination of mercury presented peculiar interest, from 

 its fluidity, and the facility with which iron might be excluded 

 from the experiment ; to make which a flat ring of box-wood 

 was cemented with wax between two circular glass discs, so as 

 to form a hollow cylinder, two inches in internal diameter, and 

 0*10 in its interior height. This being suspended, empty, by a 

 long delicate silk-thread over the horse-shoe magnet, was not in 

 the slighest visible degree affected by its rotation, however long 

 continued. It was then detached and filled with mercury, 

 which, from having been thrice distilled, and afterwards having 

 stood upwards of a twelvemonth in a bottle in contact with a 

 solution of the nitrate of that metal, might assuredly be regarded 

 as absolutely free from iron. Being again suspended as before, 

 it now readily, though feebly, obeyed the rotation of the magnet 

 in either direction, being fully commanded by it, and set in 

 motion, stopped, or reversed in its gyrations at pleasure by 

 merely continuing or changing properly the motion of the 

 magnet. This experiment was witnessed, among others, by our 

 illustrious President. The place which mercury appears to hold 

 in the scale of magnetic energy was judged to be between anti- 

 mony and bismuth, certainly superior to the latter, and certainly 

 inferior to lead. 



In wood, glass, wax, rosin, sulphur, sulphuric acid, water, &c. 

 we have not hitherto succeeded in obtaining unequivocal traces 

 of magnetism. The experiment with unannealed glass succeeded 

 no better than with annealed. In the case only of one non- 

 metallic body (unless a minute portion of iron present may have 



