INTRODUCTION
XXV
diction or improbability, and so long as anything of that sort is
left I can scarcely take my mind away from it. Then the
formulæ which I have deduced for the accurate solution are so
complicated that it takes a lot of time and trouble to make out
clearly their meaning. But if I take up a book or try to do
anything else my thoughts continually hark back to it. Shouldn't
things happen in this way or that? Isn't there still some contra-
diction here? All this is a perfect plague when one doesn't attach
much importance to the result.
Soon afterwards Hertz had to remove to Kiel. This
removal, his induction, and his lectures there took up much of
his time, so that his investigation on floating plates was not
published until a year later. Its place was taken by the
investigation on the fundamental equations of electromagnetics
(XVII.) At this time he kept a day-book, from which it
appears that in May 1884 he was alternately working at his
lectures, at electromagnetics, and at microscopic observations
taken up by way of change. On six successive days there are
brief but expressive entries-"Hard at Maxwellian electro-
magnetics in the evening," "Nothing but electromagnetics";
and then follows on the next day, the 19th of May-" Hit
upon the solution of the electromagnetic problem this
morning." This will remind the reader of v. Helmholtz's
remark that the solution of difficult problems came to him
soonest, and then often unexpectedly, when a period of
vigorous battling with the difficulties had been followed by
one of complete rest.
In close connection with this subject, and immediately
following it in order of time, came the paper "On the
Dimensions of Magnetic Pole" (XVIII. in this volume).
Directly after this came the meteorological paper "On the
Adiabatic Changes of Moist Air" (XIX.) A diagram illus-
trating the latter is reproduced at the end of this volume
from the original; the drawing of this, as a recreation after
other work, seems to have given Hertz great pleasure.
We may complete our account of Hertz's scientific work
during his two years at Kiel by adding that at this time he
repeatedly, although unsuccessfully, attacked certain hydro-
dynamic problems, and that his thoughts already turned
frequently towards that field in which he was afterwards to