Description of a Magneto-Electrie Machine, §c. 138 
be attached to one pole of the battery, and the communication 
between the other extremity and the other battery pole be alter- 
nately made and interrupted by means of a rasp or toothed wheel, 
magnetism will be induced and destroyed in the iron bar and con- 
sequently an electric current will circulate through the fine wire. 
The use of the brass disk is to prevent by means of a closed cir- 
cuit, any immediate induction in the fine from the coarse wire, 
which would inevitably take place were none interposed, and 
which would convert the instrument from a enGRSaineis to 
an electro-magnetic machine. - 
Since the above was devised, an obvious improvement has sug- 
gested itself. This is founded upon the fact. that magnetism is 
strongest at the extremities of bodies; and consists simply in di- 
viding the bar into three equal spaces by means of two disks of 
brass similar in size to the one already described. The central 
division is then to be wound -with the coarse and the two outer 
or polar divisions with the fine wire, connecting the two outer 
helices in such. a manner that they may form one long wire. 
The battery current is then to be passed through the coarse wire, 
and the connection made and interrupted as before by a rasp or 
other interrupting apparatus. As thus constructed, the instru- 
ment would produce effects similar to the common magneto-elec- 
tric machine when used for shocks or decomposition. If it be 
desired to produce sparks and deflagrations, it would only be ne- 
cessary to slide off the coils of fine wire from the poles, and to 
substitute in their stead others made of coarse wire of shorter 
length and then transmit and interrupt the current through the 
central coil as before. We should then have within a much 
smaller compass, an instrument capable of producing all the ef- 
fects of the common machine of Mr. Saxton, and by combining 
a number of such bars we might form in a comparatively small 
compass a magneto-electric battery of great energy. Some of 
Dr. Page’s beautiful interrupting apparatus might doubtless be 
used successfully with this instrument. As I have no opportu- 
nity to construct the instrument myself, I would suggest the trial, 
especially of the latter form of apparatus, to any who may be in- 
terested in the subject. Should it succeed, its advantage would 
be its superior woundese and power, (2) and the little space it 
would occupy. | 
About the same time that the above instrument was devised, 
in looking over the list of substances which are capable of form- 
r 
