flowing by the position taken by the needle relative to the conductor.

In the matter of ampere turns, as another example, it is quite simple
to assert that a ten ampere current carried once around a soft iron
bar produces the same result as a one ampere current carried ten times
around the bar, but how much more strongly is this fact stamped upon
the memory when its truth is established by experiment?

Reading about a fact, or commiting to memory the literature of a
subject, is desirable and even necessary, but knowledge of this
character partakes more of the nature of faith than that gained by
actual experience.

Let the reader learn first all that can be learned by the aid of this
simple apparatus, then branch out to allied things, making each step
as thorough as possible, and before long he will be congratulating
himself on having gained at least an elementary knowledge of
electricity.

Very little can be done in the way of electrical experiment without an
electrical generator of some sort, and nothing at present known can
excel a battery for this purpose. Although not the most desirable
battery for all purposes, that shown in Fig. 1 is the most desirable
for the amateur who desires a strong current for a short time. It is
formed of two plates, a, of carbon arranged on opposite sides of an
amalgamated plate, b, of zinc, and separated from the zinc by strips
of wood. Bars of wood are placed outside of the carbon plates, and the
four bars are fastened together by two common wood screws, thus
clamping all the bars and the zinc and carbon plates securely in the
position of use.