nd
reasonable doubt by the observations collected by Mr. Chandler. But
two of his minor conclusions, as enumerated in No. 3 of this volume,
do not seem to me well founded. They are--

"1. That the period of the inequality is a variable quantity.

"2. That the amplitude of the inequality has remained constant for
the last half century."

Professor Newcomb proceeds to give his reasons for scepticism, which are
too technical in character to reproduce here. But I will quote the
following further sentence from his paper:--

"The question now arises how far we are entitled to assume that the
period must be invariable. I reply that, perturbations aside, any
variation of the period is in such direct conflict with the laws of
dynamics that we are entitled to pronounce it impossible. But we know
that there are perturbations, and I do not see how one can doubt
that they have so acted as to increase the amplitude of the variation
since 1840."

[Sidenote: Chandler's reply.]

In other words, while recognising that there may be a way of reconciling
one of the "minor" conclusions with theory, Professor Newcomb considers
that in this case the other must go. Mr. Chandler's answer will speak for
itself. It was delayed a little in order that he might present an immense
mass of evidence in support of his conclusions, and was ultimately printed
on August 23, 1892.

"The material utilised in the foregoing forty-five series aggregates
more than thirty-three thousand observations. Of these more than
one-third were made in the southern hemisphere, a fact which we owe
principally to Cordoba. It comprises the work of seventeen
observatories (four of them in the southern hemisphere) with
twenty-one different instruments, and by nine distinct methods of
observation. Only three of the series (XXI., XXV., and XXXV.), and
these among the least precise intrinsically, give results
contradictory of the general law developed in No. 267. This degree of
general harmony is indeed surprising when the evanescent character of
the phenomenon under investigation is considered.

"The reader has now before him the means for independent scrutiny of
the material on which the conclusions already drawn, and those which
are to follow, are based. The space taken in the printing may seem
unconscionable, but I hope this will be