DR. O’SHAUGHNESSY’S CONTRIVANCE DESCRIBED. 
435 
instead of B, still the same effect was pro- 
duced. I was for some time altogether un- 
able to account for this occurrence, but deem- 
ing it likely that the momentary interruption 
of the circuit, caused by moving the wires, 
might have enabled the electricity to accu- 
mulate and act with greater inducing energy 
on the restoration of the circuit, additional 
experiments were made which justified this 
view of the subject. 
If, when the pole wires of A were media, 
nically changed, the circuit was broken in B, 
by removing one of the wires for an instant 
from its plate, and then replacing it, both 
galvanic currents then acting with equal 
energy, the magnets held their respective 
polarities : no overpowering took place, and 
A ceased to attract B, which accordingly was 
repelled. I should oliserve, that mechanical 
supports and guides were used in the experi- 
ment, which I have not delineated in the 
diagram. 
This fact of the increase of magnetic energy 
given by interrupting the circuit, is one of 
much practical moment. It is a necessary 
consequence of the restoration of electric 
intensity, brought about by the breaking of 
the circuit which Marianini described in 1828, 
in his paper in the 38th vol. of the Annales 
de Chemie. I am not aware that the effect 
of this renovation of power on the electro- 
magnet has been previously studied. It is 
well exemplified by an experiment which may 
be readily performed. If we excite an 
electro-magnet by a battery of 10 pairs of 
Wollaston plates, 100 water, 2 sulphuric, and 
1 nitric acid, by carefully but rapidly loading 
the magnet, we find its maximum sustaining 
power, say 20 lbs. ; add another pound, and 
the keeper and weights fall off. If we now 
attempt to load the magnet again, we find it 
will not support more than half its previous 
charge. But if we remove one of the wires 
for a moment from the circuit and then re- 
place it, the magnet will then sustain the 
same weight as at first. Or we may take the 
experiment under another modification. 
Load the electro-magnet with its known 
maximum weight, say 20 lbs., and allow the 
action to proceed till the weakening energy of 
the battery allows the weight to fall spontane- 
ously ; try to replace it on the instant ; the 
electro-magnet will seldom support as much 
as 5 lbs. ; but if we interrupt the circuit for 
a moment, it will support 18 or even 19 lbs., 
and allowing the successive charges to 
fall, and repeating the experiment, we find the 
magnetic force sink gradually to zero as the 
force of the galvanic action declines. 
To revert to the overpowering of the poles 
in the instances above mentioned, further 
experiments shewed that this action only 
occurred when the metallic surfaces of the 
bars were actually in contact, and that the 
interposition of even one leaf of paper glued 
on the polar surfaces prevented the effect in 
question. 
The practical applications of these facts in 
the construction of machinery to be worked 
by electro-magnet, will be sufficiently ob- 
vious in the sequel of this paper, and on pe- 
rusal of Mr. M’Gauley’s article in the Ap- 
pendix^. Another and an interesting question 
presented itself before any wheel model could 
be constructed ; viz. — whether, on the excite- 
ment of more than one electro-magnet by 
the same galvanic battery, the magnetic force 
was divided in any definite proportion between 
them. 
The apparatus, No. 2, delineated in the 
plate, was employed to decide this question. 
It consists of a small wooden table-shaped 
frame, on which several small electro-magnets 
may be placed, so that ends of the spirals of 
one or more may be dipped into little cups 
of mercury and removed at pleasure, without 
disturbing the general arrangement. One of 
the set is placed with its legs vertically, so 
that a keepei, scale, and weights can be at- 
tached to it. 
d’he experiments were made vvith 12 small 
horse-shoe electro-magnets, two inches long, 
half inch diameter, one inch interval between 
the poles, and each wound with an equal 
length of silk covered wire. The battery em- 
ployed was ten 4-inch plates of Wollaston’s 
construction — exciting liquid, as in all these 
experiments, lOOwaier, 2 sulphuricy 1 nitric 
acid. On exciting the trial magnet or No. 1, 
it supported 8 lbs. 4 oz. The wires of No. 2 
were introduced, and No. 1 then supported 
but 4 lbs. 3 oz. Three were excited in the 
same way, and the weight supported was 2 
lbs. lO oz. When four were excited. No. 1 
held up 2 lbs. 2 oz. With five, 1 lb. 6 oz. 
The numbers continued falling by the suc- 
cessive partition.of the excitement, very nearly 
in a direct arithmetical subdivision. When 
all twelve were in connexion with the bat- 
tery, the trial magnetsustained butsix ounces. 
In all these experiments attention was in- 
variably paid to breaking the circuit on each 
fall of the weights, in conformity with the ex- 
periments a^ ove described. On completing 
the series ofl2, the first experiment on No. I 
by itself was always repeated, in order to as- 
certain how much of the decrease of power 
might be attributable to loss of power in the 
battery. With the proportion ofacids, above 
described, the action is so constant and gentle 
that the weight first sustained by No. 1 was 
easily supported again. 
This experiment was tried repeatedly, and 
always with the same results. It shews that 
the electric force, when thus '^arithmetically 
subdivided, induces a directly proportioaate 
and less degree of magnetic power. 
Having thus given a brief exposition ofthe 
electro-magnetic facts, essential to be under- 
stood as a clue to the formation of an electro- 
magnetic engine or machine, I proceed to de- 
scribe the model I have constructed, such as 
it was exhibited at Lord Auckland’s soirde on 
the9th of November. 
It consists essentially of the following parts. 
1st, THlt. WHEEL, 
Of which the frame is made of liaht wooden 
disks, eight inches in diameter, two and half inches 
interval at the circumference lietween the disks, 
which are fastened on a coricentric woodvn sup- 
port, and mounted on a steel axle half an inch in 
diameter. Around this wheel, at imervais of two 
* Vide our Review, page 335. 
