OCTOBER 29, 1897. ] 
time, disintegrate. There are also diamonds 
of all colors and qualities which are found in 
the mines in a broken state. These are not 
cases of fracture in mining, whether by the use 
of explosives or otherwise. The fragments are 
embedded in the matrix and the crytals have 
been broken before final consolidation of the 
lava took place. They seem precisely analo- 
gous to the broken phenocrysts of hornblende 
or feldspar not infrequently found in lavas and 
such as Lewis found in kimberlite ; it is asserted 
that in a solitary case two complementary por- 
tions of a single diamond have been found, one 
of them coming from a depth of two hundred 
feet greater than the other.* 
Mr. Kunz inclines to ascribe the fracturing 
of diamonds to the brecciation of the lava. If 
this were the correct explanation one would 
expect to find the diamond fragments only at 
the surfaces of rock fragments, and to hear of 
complementary portions of-diamond crystals 
found near together. 
still embedded fragments which I had an 
opportunity of inspecting did not bear out the 
theory of brecciation fracture, and I have noted 
above the only instance I could learn of in 
which complementary fragments have been dis- 
covered. It seems to me more probable that 
the diamonds and other fractured phenocrysts 
in massive lavas have been broken at the 
moment of explosive ejection from the volcanic 
melting-hearth. 
Iam not in a position to discuss Sir Henry 
Roscoe’s discovery of a soluble hydrocarbon in 
the blue, for I donot know whether the massive 
lava free from shale, in the deeper workings, 
does or does not contain it. If it does, the 
origin of this substance would probably be most 
easily explained as similar to that of the 
erystallized carbon, and as due to some such 
process as that to which Mr. Mendeleeff ascribes 
the formation of the Baku petroleum, the 
decomposition of carboniferous, terrestrial, 
metallic iron. 
In closing this criticism it is appropriate to 
quote the opinion of Mr. Gardner F. Williams,+ 
*. J. Loomis, Eclipse party in South Africa, 
1896, p. 121. 
+ Second annual report of the De Beers consolidated 
mines for the year ending March 31, 1890. In this 
SCIENCE. 
The few specimens of - 
667 
a mining engineer who for many years has 
managed the De Beers consolidated mines with 
conspicuousability. ‘‘ The proofs are most con- 
clusive that the diamonds were not formed in 
situ, but have come up from below with the blue 
ground.”’ 
GEORGE F. BECKER. 
WASHINGTON, D. C., October, 1897. 
NOTE ON ‘ THE EASTERNMOST VOLCANOES OF 
THE UNITED STATES.’ 
In a letter published in ScrencE (Vol. VI., 
No. 146, pp. 594-595, October 15, 1897) Mr. 
Robert T. Hill tries to correct the map showing 
the distribution of voleanoes in the United 
States, plate 5, published in ‘ Professor I. C. 
Russell’s magnificent volume on the Volcanoes 
of North America.’ Hesays the ‘‘ conclusions on 
the part of Professor Russell are erroneous and. 
mar his otherwise excellent work, for some of 
the most beautiful and perfect voleanice craters 
in the United States occur in New Mexico.’’ 
Consequently Mr. Hill gives a sketch of the New 
Mexican region, giving ‘supplementary data 
concerning the distribution of voleanie phe- 
nomena.’ Among the omissions of the true 
craters of New Mexico, which have escaped Mr. 
Russell’s notice, the groups of volcanic cones 
and craters with flows of lava, called the Cer- 
rito, lying between Galisteo and the Rio Grande 
are quoted in the letter, but erroneously marked 
in the accompanying sketch as forming a line 
of three black discs or craters at the western 
report Mr. Williams quotes Stelzner as having deter- 
mined the ‘snakedike’ as pikrite porphyry and the 
blue ground as essentially the samerock. The mela- 
phyre sheet underlying the bituminous shale Stelzner 
considered as olivine diabase. Mr. Williams prob- 
ably took these determinations from letters, for I can 
find no publication by Stelzner on the subject until 
1893 (Isis Society, Dresden). In this paper Stelzner 
adopted Lewis’ term ‘kimberlite’ for the blue ground. 
He assented to Knop’s view, that the kimberlite 
magma was itself carboniferous or hydrocarboniferous 
and that the diamond crystallized out as a primitive 
rock constituent. He mentioned, as of special bearing 
on this subject, a specimen presented by Mr. Williams 
to the Freiberg Museum, a fragment of diamond which 
is intergrown with pyrope and is thus presumably 
from the same habitat as this essential element of the 
kimberlite. 
