comment upon certain criticisms with which some of these Essays have
been met.

But, on turning the matter over in my mind, I began to fear that a
formal dedication at the beginning of such a volume would look like a
grand lodge in front of a set of cottages; while a complete defence of
any of my old papers would simply amount to writing a new one--a labour
for which I am, at present, by no means fit.

The book must go forth, therefore, without any better substitute for
either Dedication, or Preface, than this letter; before concluding which
it is necessary for me to notify you, and any other reader, of two or
three matters.

The first is, that the oldest Essay of the whole, that "On the
Educational Value of the Natural History Sciences," contains a view of
the nature of the differences between living and not-living bodies out
of which I have long since grown.

Secondly, in the same paper, there is a statement concerning the method
of the mathematical sciences, which, repeated and expanded elsewhere,
brought upon me, during the meeting of the British Association at
Exeter, the artillery of our eminent friend Professor Sylvester.

No one knows better than you do, how readily I should defer to the
opinion of so great a mathematician if the question at issue were
really, as he seems to think it is, a mathematical one. But I submit,
that the dictum of a mathematical athlete upon a difficult problem which
mathematics offers to philosophy, has no more special weight, than the
verdict of that great pedestrian Captain Barclay would have had, in