'SUBTLE is THE LORD' 123molecular forces being affected by the motion. The author clearly has in mind a
dynamic contraction mechanism which presses the molecules together in their
motion through the aether.
FitzGerald's hypothesis was referred to several times in lectures (later pub-
lished) by Oliver Joseph Lodge [B3]. Larmor, too, properly credited FitzGerald
in the introduction to the latter's collected works: 'He [F.] was the first to suggest
... that motion through the aether affects the dimensions of solid molecular aggre-
gations' [L9]. Elsewhere in that same book, we find FitzGerald himself mention-
ing the contraction hypothesis, in 1900. In that year, Larmor's essay Aether and
Matter [L10] had come out. In a review of this book, FitzGerald wrote that in the
analysis of the Michelson-Morley experiment 'he [Larmor] has to assume that
the length of a body depends on whether it is moving lengthwise or sideways
through the ether' [Lll], without referring, however, to his own suggestion made
more than ten years earlier!
FitzGerald's curious silence may perhaps be explained in part by what he once
wrote to his friend Oliver Heaviside: 'As I am not in the least sensitive to having
made mistakes, I rush out with all sorts of crude notions in hope that they may
set others thinking and lead to some advance' [ F4]. Perhaps he was also held back
by an awareness of those qualities of his which were described by Heaviside soon
after FitzGerald's death: 'He had, undoubtedly, the quickest and most original
brain of anybody. That was a great distinction; but it was, I think, a misfortune
as regards his scientific fame. He saw too many openings. His brain was too fertile
and inventive. I think it would have been better for him if he had been a little
stupid—I mean not so quick and versatile but more plodding. He would have
been better appreciated, save by a few' [O2].
Lorentz was one of those few who appeciated FitzGerald the way he was.
4. Lorentz. The first paper by Lorentz relevant to the present discussion is
the one of 1886—that is, prior to the Michelson-Morley experiment—in which
he criticized Michelson's theoretical analysis of the 1881 Potsdam experiment
[L3]. The main purpose of Lorentz's paper was to examine how well Fresnel's
stationary aether fitted the facts. He therefore reexamined the aberration and
Fizeau effects and noted in particular another achievement (not yet mentioned) of
Michelson and Morley: their repetition of the Fizeau experiment with much
greater accuracy, which bore out Fresnel's prediction for the drag coefficient in a
much more quantitative way than was known before [M17]. Since at that time
Lorentz had a right to be dubious about the precision of the Potsdam experiment,
he concluded that there was no particular source for worry: 'It seems doubtful in
my opinion that the hypothesis of Fresnel has been refuted by experiment' [L3].
We move to 1892, the year in which Lorentz publishes his first paper on his
atomistic electromagnetic theory [L12]. The Michelson-Morley experiment has
meanwhile been performed, and Lorentz is now deeply concerned (as was noted
before): 'This experiment has been puzzling me for a long time, and in the end I
have been able to think of only one means of reconciling it with Fresnel's theory.