Bb aa 
a ee 
Electro-Magnetic Apparatus. 89 
most advantageous direction, yet as these forces are oblique, the re- 
sultant is not equal to the sum of the components. Some of the fore- 
going results, however, suggest a method of approximating them al- 
most indefinitely. As an electrical current at right angles to the axis 
of a magnet is known to increase its magnetism, and one parallel to 
the axis to diminish it, the problem resolves itself into this; to cause 
the electricity to enter, in equal quantities at all points of one extremi- 
ty of the sheet, and to pass out in a similar manner at the other ex- 
tremity, and also to exert the least magnetic effect possible, in pass- 
ing toand from these points respectively, in directions parallel to the 
axis. Now, from a comparison of some of the results which have 
been stated in this paper, we may infer that there is a vast dispro- 
portion between the magnetizing effect of an electric current, moving 
near the temporary magnet, by means of a broad sheet of metal, and 
the effect of the same quantity of electricity conveyed in an equal por- 
_ tion of time, and at the same distance from the magnet, by a wire or 
tod, ofa length equal to that of the sheet, and of a size adequate to 
the ‘Supply of the requisite quantity of electricity to the sheet, when 
tods or wires are used merely as conductors between the extremities 
of the sheet and the battery, and not for producing electro-magnetic 
effets directly. ‘This principle suggests the employment of a single 
cylindrical tod at each end of the sheet, for establishing a communica- 
tion between the latter and the wires of the battery, each rod being 
parallel tothe magnetic axis, and connected with the end of the sheet, 
either Continuously or by numerous points or wires, the connecting 
Patts being in either case so graduated in thickness, as to compensate 
‘or the variable intensity of the electricity in different sections of the 
rod, and thus transmit equal quantities to equal portions of one ex- 
Temity of the sheet, and also equal quantities from equal portions of 
the other extremity of the sheet to the rod. ‘The magnet itself should 
Constitute the rod at the interior extremity, in order to avoid the re- 
“ abt * current to an-unnecessary distance.* For this purpose 
shown hg of iron, would be preferable to a hollow one. I have 
+ nm Practicability of making the magnet itself a part of the cir- 
horse. © Proper place for the direct attachment of the wires to a 
~ "1€ magnet would be on each side of the middle of the arch. 
* 
ieee on ton necessary in the annexed drawing, if we wished to repre- 
brass rog to ey with this improvement, would be a ridge on the roll to show the 
V ich ff are attached. 5 
OL, XXL—Np. 7 3 
* 
