EXPERIMENT’S ON THE GALVANIC BATTERY AND ITS CHARGE. 535 
Mr. M’Gauley thought it would be 
unbecoming in him to suggest anything 
to the British Association; but he be- 
lieved nothing would be more condu- 
cive to the interests of science, than 
that the Association should cause to be 
instituted a series of experiments on 
the Galvanic Battery and its Charge, 
which would set all questions on the 
matter at rest for ever. Before he left 
this part of the subject, he thought it 
well to recall the attention of the Sec- 
tion to the nature of the power obtained 
by electro-magnetism. In steam, one 
great cause of the varying power of the 
engine arises from the varying leverage 
of the crank. Let b and b’ be posi- 
tions of the extremity of the pistonrod, 
c’ R and c’ r’ corresponding positions 
of the crank, the leverage of the crank 
is measured by the perpendicular c’ p 
and c’ p’. It varies as that perpendi- 
cular. But in electro-magnetism, the 
force at b, say the bar traversing be- 
tween the magnets, is always varying. 
He would not then enter into some 
curious results obtained by calculation 
on this matter.* 
He had been anxious to satisfy him- 
self, by his own experiment, of the 
truth of the law of magnetic attraction 
being in the proportion of the inverse 
square of the distance, but abandoned 
the inquiry for the present, when he 
found that a magnet, with a seemingly 
appropriate bar, would lift at one-six- 
teenth of an inch only five pounds ; 
though with a different bar it lifted the 
same weight at twelve times the distance; 
and that the greater the distance 
through which powerful attraction might 
be exerted, the less the lifting power 
appeared. 
Identity of Magnetism and Electricity. 
— In examining the identity of electrici- 
ties derived from different sources, it 
seemed to Mr. M’Gauley that we some- 
times forget that electricity may be 
modified both as to quantity and inten- 
sity ; and that if either be changed, or 
both, we cannot expect the same results. 
To test, therefore, the identity of any 
agent with electricity, we must not use 
those means which are the measure of, 
or dependent on, either quantity or in- 
tensity ; for if in such experiments the 
electrometer or galvanometer be not af- 
fected, we only arrive at a negative con- 
• See plate Iv. fig 6. 
elusion— that if the agent under consi- 
deration be electricity, it differs from the 
ordinary electricity in quantity, intensity 
or both. For though we never had been 
able with galvanism to cause the leaves 
of the electrometer to diverge, or with 
machine electricity to deflect the galva- 
nometer, or with electricity to produce 
magnetism, or with magnetism, electri- 
city, with electricity to produce heat, 
with heat, electricity — their non-identity 
would by no means follow. To examine 
with ease and certainty the identity of 
anything with electricity, we must find 
some property of electricity, which is not 
modified by, nor dependent on, quantity 
or intensity. We know, and chemistry 
furnishes us with one proof, that the 
elements of things may be the same as to 
quantity, and as to the intensity of mu- 
tual action ; and yet maybe productive of 
vastly different effects. Thus we know, 
that from two equal volumes of carbon 
and hydrogen, may be formed at least 
three very different substances. 
The following facts seem to afford ad- 
ditional evidence of the perfect identity 
of electricity and magnetism; and that 
magnetism does not require, nor sup- 
pose, the circulation of electrical cur- 
rents. 
1st. A shock and spark are obtained 
by means of an electro-magnet only af- 
ter battery communication is broken ; 
for no matter how long this communica- 
tion is maintained, neither shock nor 
spark shall be perceived. 2ndly. The 
shock and spark are not the effects of 
the battery ; for to obtain a shock — 
(this shock he had not seen remarked 
by any experimentalist) — it is not ne- 
cessary to form a part of the communi- 
cation between the copper and zinc, but 
merely between the extremities of the 
helix, or between either extremity of 
the helix and the copper or zinc of the 
battery. 3rdly. The shock and spark 
do not arise from the magnetism of the 
bar included in the helix, since the more 
perfectly the bar is demagnetized in 
breaking contact the better. Besides, it 
is curious that a powerful shock and bril- 
liant spark may t)e obtained without any 
iron, and from a heap of wire thrown 
without any heliacal arrangement. This, 
Mr. M‘Gauley remarked, would lead to 
a very simple and effective electrical 
apparatus, one easily managed, and al- 
ways ready for use; the length and 
number of the coils, with a given calori- 
