INTRODUCTION
xi
avoided. And so I ask you, dear father, for your decision rather
than for your advice; for it isn't advice that I need, and there is
scarcely time for it now. If you will allow me to study natural
science I shall take it as a great kindness on your part, and what-
ever diligence and love can do in the matter that they shall do. I
believe this will be your decision, for you have never put a stone
in my path, and I think you have often looked with pleasure on
my scientific studies. But if you consider it best for me to con-
tinue in the path on which I have started (which I now doubt),
I will carry out your wish, and do so fully and freely; for by this
time I am sick of doubt and delay, and if I remain in the state I
have been in lately I shall never make a start. . . . So I hope to
have an early answer, and until it comes I shall continue to think
the matter over. Meanwhile I send my love to you' all, and re-
main your affectionate son,
HEINRICH.
Matters were decided as he had hoped, and, full of joy at
being able to carry out his wishes, Hertz now proceeded to
arrange his plan of studies. He remained altogether a year at
Munich. He devoted the winter-semester of 1877-78 in all
seclusion to the study of mathematics and mechanics, using
for the most part original treatises such as those of Laplace
and Lagrange. Most of the following summer-semester he
spent at practical work in the physical laboratory. By
attending the elementary courses in practical physics at the
University (under v. Jolly) and at the same time in the
Technical Institute (under v. Bezold), he was able to supple-
ment what he had already learned by means of his own
home-made apparatus.
Thus prepared he proceeded in October 1878 to Berlin,
eager to become a pupil of v. Helmholtz and Kirchhoff. When
he had arrived there, in looking at the notices on the black
notice-board of the University his eye fell on an intimation of
a prize offered by the Philosophical Faculty for the solution
of a problem in physics. It referred to the question of electric
inertia. To him it did not seem so hopelessly difficult as it
might have appeared to many of his contemporaries, and he
decided to have a try at it.
This brings us to the beginning of his first independent
research (the first paper in the present volume). We cannot
read without astonishment the letters in which this student
of twenty-one reports to his parents the starting of an in-