SE erp 
New Magnetic Electrical Machine. 167 
circuit is broken, a powerful secondary rushes in the same direc- 
tion with the primitive battery current. Hence the bright spark 
is occasioned by the passage of the secondary through the heated 
air, occasioned by the combustion of the mercury. Now, if the 
surface of the metal is covered with a non-conducting liquid, such 
as oil, the circuit is broken with precision, while an obstacle is 
offered to the consequent and secondary current, and the greater 
part of it rushes through the body, or whatever conductor joins 
the extremities of the coil. The application of this fact is of 
great value in the use of the magneto-electric machine. If a dro 
of oil be put upon the break piece of the ingenious machine of 
Clarke, its power will be greatly increased, while it preserves a 
good contact by saving the metals from oxidation. I find also, 
that if the stratum of oil be very thin, the spark is more brilliant 
than without it, being partly due to the combustion of the oil. 
The same is true also of charcoal points, when used with the de- 
flagrator or magnetic electrical machine. It will be seen at once, 
that the gain of power in this new magnetic electrical machine 
must be very great. I notice in the last No. of this Journal, 
that Clarke’s machine has on one armature four thousand five 
hundred feet of wire, whereas on one armature of this machine 
there are only eight hundred feet. The source of this superior 
action, is chiefly the use of the straight armature, instead of the 
revolving horse-shoe. There is no advantage in covering a 
horse-shoe (for electro-magnetic or magneto-electric purposes) 
beyond the straight portion. Hence the piece of iron is longer 
than necessary for the full and ready production, and neutraliza- 
tion of the magnetic forces. The straight armature is covered 
through its entire length, and covered with ease and precision in 
On a new compound Shethiceheaieily fir tha gnadeition fd c 
magnetic electrical spark, and also for attractive force.—The fol- 
lowing positions, I think, may be considered as well established 
by experiment. » Ist. Very long and large bars of soft iron, even 
with a proportionate battery, acquire a comparative feebler mag- 
netic intensity than smaller bars. 2d. That long and large bars 
of soft iron, once charged by a battery, retain a greater degree of 
magnetic power than smaller ones. The great magnet lately con- 
structed by Dr. King of this city, (Boston) in imitation of Prof. Cal- 
lan’s magnet, affords convincing proof of these facts. This magnet 
