Definite Magnetic Action 29

meter coil, it ought to have been so, because then the intensity
is lower and the lateral transmission less.

102. Hence it would appear that if the same absolute quantity
of electricity pass through the galvanometer, whatever may be its
intensity, the deflecting force upon the magnetic needle is the same.

103. The battery of fifteen jars was then charged by sixty
revolutions of the machine, and discharged, as before, through
the galvanometer. The deflection of the needle was now as
nearly as possible to the eleventh division, but the graduation
was not accurate enough for me to assert that the arc was
exactly double the former arc; to the eye it appeared to be so.
The probability is, that the deflecting force of an electric current

is directly proportional to the absolute quantity of electricity passed, v

at whatever intensity that electricity may be.1 ?ji

104. Dr. Ritchie has'shown that in a case where the intensity
of the electricity remained the same, the deflection of the
magnetic needle was directly as the quantity of electricity passed
through the galvanometer'2 Mr. Harris has shown that the
heating power of common electricity on metallic wires is the
same for the same quantity of electricity whatever its intensity
might have previously been.3

105. The next point was to obtain a voltaic arrangement
producing an effect equal to that just described (103). A platina
and a zinc wire were passed through the same hole of a draw-
plate, being then one-eighteenth of an inch in diameter; these
were fastened to a support, so that their lower ends projected,
were parallel, and five-sixteenths of an inch apart. The upper
ends were well connected with the galvanometer wires. Some
acid was diluted, and, after various preliminary experiments,
that adopted as a standard which consisted of one drop strong
sulphuric acid in four ounces distilled water. Finally, the time
was noted which the needle required in swinging either from
right to left or left to right: it was equal to seventeen beats of
my watch, the latter giving one hundred and fifty in a minute.
The object of these preparations was to arrange a voltaic appa-
ratus, which, by immersion in a given acid for a given time,
much less than that required by the needle to swing in one

1 The great and general value of the galvanometer, as an actual measure
of the electricity passing through it, either continuously or interruptedly,
must be evident from a consideration of these two conclusions. As con-
structed by Professor Ritchie with glass threads (see Philosophical Transac-
tions, 1830, p. 218, and Quarterly Journal of Science, New Series, vol. i. p. 29),
it apparently seems to leave nothing unsupplied in its own department.

2 Quarterly Journal of Science, New Series, vol. i. p. 33.

3 Plymouth Transactions, p. 22.

I
isent at one of its extremities two