SEPTEMBER 17, 1897.] 
gard to the production of this most precious of 
gems, the origin of which has beenso obscure a 
problem in mineralogy and geology. Another 
point of great scientific interest developed in the 
course of these investigations is the close simi- 
larity, both in composition and in structure, 
existing between some of these rarer igneous 
rocks of our globe and the extra-terrestrial vis- 
itants that come to us from space. 
Mr. G. F. Becker, in a recent letter, takes a 
different view of this subject and holds that I 
have misinterpreted Professor Lewis, and that 
he did not regard the diamonds as due to car- 
bonaceous matter taken up from the shales. 
He claims that ‘‘ Lewis over and over again 
says that the diamond is as much a part of the 
Kimberlite as its other component minerals.’’ 
It is true that he did use such an expression of 
‘the Kimberley rock’ (p. 44); but this is in 
summing up his argument that the diamonds 
are in their original matrix, as against the early 
notion of their having been washed into the 
‘kopjes’ from above, or the later theories of 
their having been carried up with the igneous 
rock from some deeper source below. The 
statement relates merely to ‘the matrix of the 
diamond ’—the subject of the article—not to 
the source of the carbon. Moreover, diamonds 
are not present in the Kimberlite of Syracuse, 
N. Y., or of Elliott County, Kentucky,* which 
Professor Lewis recognized as the same rock. 
He says (p. 56): ‘‘In mineral composition, in 
eruptive character, in structure, in enclosures, 
the three rocks are identical.’’ Itis plain, there- 
fore, that he did not regard diamonds as an essen- 
tial ingredient of Kimberlite. As to their source 
being carbon derived from the shales, it is true 
that Professor Lewis does not in these papers 
distinctly so assert, though he refers frequently 
and pointedly to the association of diamonds 
with the penetrated and included shales. But 
in personal conversation, at a period between the 
dates of his two papers, and before he had even 
heard of the very suggestive experiment of Sir 
Henry Roscoe, Professor Lewis expressed to 
the writer his definite belief that such was their 
origin. The knowledge of this fact may have 
* Ts there a diamond field in Kentucky ? J. S. Dil- 
ler-G. F. Kunz, Screncr, Vol. X., 1887, pp. 140- 
142. 
SCIENCE. 
455 
led me to state this view as held by Professor 
Lewis more clearly than appears on the face 
of his paper, and doubtless explains the perplex- 
ity that Mr. Becker expresses as to how he and 
I can read the article differently. 
Mr. Becker says: ‘‘I consider the diamonds 
as much a part of the Kimberlite as zircons are 
a part of granites.’”’ This may be Mr. Becker’s 
view; and he is a high authority, with whom I 
would not lightly disagree ; but it can hardly 
be claimed as the view of Professor Lewis, 
when he asserts (as above noted) the absolute 
identity of the diamond-bearing Kimberlite of 
Africa with the non-diamond-bearing rocks of 
Syracuse and Kentucky. The question is not 
whether the diamonds (in Africa) are ‘a part 
of the Kimberlite.’ Undoubtedly they are so, 
there ; but how came they to be so at that lo- 
cality and not at the others? This subject was 
fully discussed by the writer in ‘Gems and 
Precious Stones of North America,’ pp. 32-34, 
in connection with the examinations made by 
Mr. Diller and myself in 1887, as to the possi- 
ble occurrence of diamonds in Kentucky, as 
suggested by the similarity of the rock. It was 
there shown that, while the shales penetrated 
by the African Kimberlite had 37.50 per cent. 
of carbon, those traversed by the Kentucky 
Kimberlite contained but 0.68 per cent. The 
same rock breaks through a body of shale in 
two localities, the one rich in carbon, the other 
poor; the intruding rock is fitted with dia- 
monds in the former case and none appear in 
the latter. And why did Lewis search every- 
where for localities where serpentines and per- 
idotites occurred associated with coal forma- 
tions ? 
Professor Lewis observes (p. 8): ‘‘The rock 
(at Kimberley) appears in two types, one not 
bearing diamonds, the other diamantiferous, 
and the distinction between them is suggestive. 
Both oceur in the same mine and are dark, 
compact, heavy rocks, closely resembling one 
another and differing mainly in the fact that 
one is free from enclosures of foreign substance, 
while the other is full of fragments of shale and 
other impurities. It is the latter which is dia- 
mantiferous.’? On p. 46 he notes the fact that 
the fragments of shale included in the igneous 
rock have lost their carbonaceous matter; and 
