It is only when theory and practice, study and experiment, go hand in
hand that any true progress is made in the sciences. A head full of
theory is of little value without practice, and although the student
may apply himself with all his energies for years, his time will, to a
great extent, have been spent in vain, unless he by experiment rivets
the ideas he gains by his study.
In the study of electricity, for example, let the student try to
remember the position a magnetic needle will take when placed below or
above a conductor carrying a current which flows in a known direction.
Without experiment there are nine chances of forgetting to one of
remembering; but let the student try the experiment, and he will ever
afterward be able to determine the direction in which the current is
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.
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