PREFACE
ix
any
rate in 1887, and, so far as I know, at the time of his death. Of the
third section nothing had been written ; the materials consisted only
of some very brief 'jottings ' and a small set of rock specimens. The
latter, however, appeared to me to have such an important bearing on
the subject of the first two sections that I have drawn up a statement
of the facts concerning them from such literature as I have found, and
have written some brief descriptions of the structures, macroscopic and
microscopic, of the specimens themselves.
In
addition to the above-named materials, Professor Lewis left numerous
notes on the occurrence of diamonds in other countries, and on various
matters bearing more or less indirectly on the subject of the two
papers. Two pocket-books also were placed in my hands, containing
memoranda of a journey through some districts in the United States
where diamonds had been, or were said to have been, discovered. From
these I compiled two other sections, weaving the materials of the
latter, after considerable condensation, into a continuous narrative.
The manuscript was set up in type, but Professor Eosen-busch, to whom
the whole of the proofs were submitted, was of opinion that they would
not augment the value of the earlier part of the book, because the
notes on localities were obviously incomplete, and the journeys were
more negative than positive in their results. Moreover, many of the
facts recorded had already, owing to the lapse of time, become
incorporated into literature readily accessible to students. I had
myself felt a like misgiving, but, for a reason which will appear
below, felt bound to alter or to cancel as little as possible. But when
fortified by such an authority on this special topic as Professor
Piosenbusch, in whose laboratory at Heidelberg much of the work
