Electro-Magnetic Apparatus. 87 
advantageously employed. A horse shoe magnet would require two 
such rolls or transverse coils, unless it were bent at right angles near 
each pole. 
Will you do me the favor to insert this article in the forthcoming 
number of the American Journal of Science,* and oblige yours 
respectfully, ‘ B. F. Jos. 
Schenectady, June 25, 1831. 
EXPLANATION OF THE PLATE. 
a The roll composed of silk and copper lamine, turning twelve 
times round a small hollow cylinder of soft iron, and prevented from 
uncoiling by the two copper bands or hoops 66. When the copper 
is exterior to the silk, the bands are made of some imperfectly con- 
ducting material. 
ce The two projecting extremities of the hollow iron cylinder, 
which is a small piece of thin gun-barrel. 
dd A brass rod passing through it, and resting at the extremities 
on the upright columns of the supporting frame. 
ee A brass wire bent horizontally into a semicircular form, for sup- 
Porting the small galvanic element 7, composed of two connected cop- 
Per cylinders and an intermediate one of zinc and immersed in a cup 
of acid nn, which last is drawn transparent for better illustration. 
ff Two slips of sheet copper, the upper ends of which are solder- 
ed to the two corners of the outer extremity of the copper sheet, and 
the lower ends immersed in the mercury of the cup which is soldered 
to the zine pole & of the galvanic apparatus. 
88 Similar conductors connecting the copper pole / with the ex- 
temities of the iron cylinder ec, and consequently with the interior 
extremity of the copper sheet which is soldered to it. 
A semicircular bar of soft iron, weighing 1 lb. and having at 
each end a semicircular notch, adapted accurately to the lower side 
of the Uncovered part of the hollow iron cylinder ce. : 
_ Atthe middle of this armature or lifter AA, is a hook from which 
'S Suspended the 14 Ib. weight m. 
One peculiarity of my electro-magnet apparatus, above described, 
~~ substitution of the roll for the helix. As 1 stated eight years | 
8% “it is the transverse. or circular and not the spiral direction 
* 
' Ane above arrived too late for the last No. (that for July, 1831.) 
26 to the oblique spiral or helix then employed. 
