The sun. [volume] (New York [N.Y.]) 1833-1916, 1897-08-01
THE GENESIS OF THE DIAMOND.
A Review or tho Poathumous Publication OF
Pror. Lewia'a Lectures.

There has been published recently n volume
OF small size, but Of especial interest and i'm
p%ortanoc, in regard TO tho origin of diamonds.
This lis none other than the posthumous issue of
tho full papers OF the late Prof. II. CarNill Lewis,
edited by his friond. Prof. T. @. Bonnoy OF Lon
don. cit will be remembered that Prof. Lewis
was tho first to present n clear and definite
theory Of tho origin Of tho South African dia-
monds, rs resulting from the intrusion Of
igneous rocks Into and through carbonacoous
shales, and the capitalization OF the carbon
throughout tho rock as 1t cooled, from hydro
oarbons distilled from the shale that had been
broken through. These views, now for the
most part accepted. and subsequently con-
frmed by other and very interesting parallel
discoveries, he presented In two papers read be-
fore the British Association for the Advance
ment OF Science at its meetings held in 1885,
at Birmingham, and in 1887, at Manchester.
Before he was able, however, to prepare them
for publication and carry them to tho greater
completeness that he desired, Prof. Lewis sue.
cunbed to an attack Of typhoid fever, which re-
moved one Of the most brilliant and capable OF
the rising scientists of this country. Agree
ably to his expressed wishes, his material was
intrusted to his friend and co-laborer, Prof.
George II. Williams OF Johns Hopkins Univer-
sity; but by a strange fatality, before the latter
had time to arrange and edit these papers, he,
too. fell a victim to the same disease, in 1894.
The work was then onmitte to Prof. Bonney,
and at last is given to the scientific world.
The book consists of an Introductory note by
Mrs. Lewis; a preface by Prof. Bonney the two
papers Of Prof. Lewis himself, with some later
notes and references by the editor; a brief &C.
count Of similar material from other localities,
belonging to Prof. Lewis. also by tho editor; q
closing note on some MSS. of Prof. Lewis, and
n full index. There are also two plates and a
number Of smaller illustrations, the latter from
Prof. Lewis's own drawings.
Tho first paper, "On a Diamond Bearing
Peridotite and on the History OF the Diamond"
(1SS6), is brief. dealing with the character and
occurrence Of the diamantiferous rock at Kim.
berley and outlining Prof. Lewis's theory.
The second paper, THE Matrix OF tho Dia-
mond" t1ss7), is moro extended and goes into
an exhaustive discussion and comparison of tho
various aspects, contents, and alterations OF the
rock, which he finds to be different from any
previously described. and therefore proposes
for it the name Of Eimberlite. Its main char
acter Is that of q highly basic porphyritic per-
idotite, filled with Divine crystals and grains,
more or less altered, and various other min
erals-scrpentine, tremolise, &C., with bronzite,
rutile, perovskite, :pyropo garnets, micaceour
minerals, and other forms. and at times brec-
ciated in structure, filed with fragments Of
cGrbonaceous shale brought up from below.
The shales are Of Triassic age, the "Karoo
beds of that region, and the intrusion Of the
,,riJo,ito In tho ,,-o,t .r,noo" - ,hiun,r.t r..
4. 'n' ste"t pipes y htuHe!s 'ha1
constitute the mines Is therefore proved to be
OF a later, though not exactly determined, period.
Th. ,r.s,ion has hoon - sornn,tma.
- -
"hether the aiamonds themselves may not have
been carried up from a deeper source in rock
below instead Of originating in the peridotite,
and the occurrence Of broken crystals has been
cited in support of this view. Prof. Lewis, how
ever. disposes very COMPLETELY OF this idea in
two ways: he refers to the well known fact that
each OF the great mines or pipes yields dia-
sH. H" - ~ - speN
character peculiar TO that one ana dincrent
from the others; SO that African experts and
even those who have never been there can rec.
oShile from "hieh NINE any diamond mas come.
Further, as to the broken crystals, he shows
tha, brenkap, not ;nfrcouen,Iv occurs after m.
10. ~ o.."1' a.e ~
uialhohus are removed from the rock, ana
points out that this is a result OF strain in their
formation. as indicated by microscopical and
optical examination. and that such a condition Is
o,h,r 49,, Ttmar ha a,sad 49, aIthn' -
- "u nsAe, at'NouSn
Frof. LOWS docs not speak OF Il. that many
crystals must be broken in the blasting OF the
rock. tho shovellin- and cartinp of the loos.
80 ~ - 80 Va - ~
ehed material and the various mechanical
processes employed at the mines, and that
n,nca. NJ sucb broken cry.taIs would bo .
49, "oN 20 1tp
nralei ana scattered TO various parts OF the I'M
Ilahse aumplhg ana weetherlns hoors. never
10 ne recognized as fragments OF the same one,
MICA hha-4y recovered, perhaps AT very Gluer-
EN- tines.
Inc fooK ltSolt Is O DARK green, compact ma
ierlai, resembling seTPentlht. aud containing u
large proporIlon OF Divine IN grains and crys-
ta!s. seSeraI green minerals thal are NOT con
spieuops, from the reseniolance OF Their color,
from the ground mass ,ehstatitc' chrohie-uiop-
SIDE, slnaraSiiIe, and %oastlteI; a mica. prob
ABLY Diotlte, more consp!cnonsh ana quite aound-
ahLaho frequent grams OF pyrope garnet, some,
times ~ gem quailty ai1 great beauty ana
mlscaIleu cape ruDies. VI slhauor dis
semihateo .nllneraIs arc 10 DC noted perorskltS'
quite treqIent, ana maSnetits. cHroinate. IL
mehite' anu plcot'1e' loss so, thousn common
Itare anu minute occurrences are -Apatite,
cptuote' orthlte, lrelhoiite' lourtittinc, rull!e,
spheie ana leucoAehe. As aeconposit,on prou-
netS mere are serpehtilie aio Gazette aounuanl,
anu zontee onaIEenony. ana taic' aiso e! unite;
nose win me u!lhlohus anu tne included
Iatinents OF GAroonaceouS snale. mako up the
cohtents oil ma reinarkaole rock.
ir p LeMdS u SUes mo q h .at HUoouht
OF ihe houe or occurrence Oh Ihoee numerals,
beginning Win inc mosL conspicuous species,