Mr. MuIIins on an improved Magneto-electrical Machine. 121 



poles of each set of magneis, which influence, it can be shown» 

 does not depend upon the size of the connecting magnets, for 

 I have tried large liorse-shoe magnetic bars, single and in 

 sets, without any increase of power beyojid that obtained from 

 the small magnetic arcs represented in the figure. 



Induction is certainly a cause, but not the sole cause of the 

 inci'eased power; there are other causes, as yet unexplained, 

 which I trust may appear satisfactory to those who may per- 

 use a paper which I am now preparing on this highly inter- 

 esting subject: suffice it here to say, that in the future con- 

 struction of the instruments in question, magnetic arcs in con- 

 nexion with vertical bar-magnets should decidedly be used in 

 preference to any other form or mode of construction at present 

 known ; and I would strongly advise any person who happens 

 to have a machine of the horse-shoe form to cut off the bend 



as indicated in the annexed figure and reapply .^ 



the same or other pieces of the same size mag- // \ ) 

 netized, for by so doing it will be found that a vast 

 increase of power will be obtained. I have thrown 

 out these hints in the hope that they may lead to 

 still greater improvements in the mode of develop- 

 ing the powers of combined magnets. In concluding this subject 

 it may be well to observe that with my improved magnetic ma- 

 chine I have charged a Leyden jar, and obtained by the same 

 means various other results similar to those obtained from the 

 action of the common electrical machine. 



In conclusion I v/ould add, that in the various experiments 

 I have made in regard to the best modes of developing and 

 sustaining voltaic electricity, I have found that caoutchouc, or 

 Indian-rubber, may be used with great advantage for insula- 

 tion. I have applied it in place of glass in my intensity- 

 sustaining battery ; and as it can be made to adhere to the 

 copper and may be laid on as thin as common letter-paper, a 

 combination of plates or cylinders may be brought so close 

 together as to occupy only a third of the space filled by a si- 

 milar combination in the batteries at present used. In my 

 intensity-battery, from the advantages derived from bringing 

 the metallic cylinders as close as possible, this mode of insu- 

 lation is most convenient and satisfactory, 



I am, Gentlemen, yours, &c. 



House of Conimoni, July 1, 1836, FreD.W. MulLINS. 



Third Series. \o\. 0. No. 52. Aug. 1836. 



