FOREIGN CORRESPONDENCE. 
161 
on the " Orgiiuization of Trilobites," called it Fhacops caudatus, which 
generic determination modern palceontologists have followed. 
One of the chief featnres in the species is the great prominence of 
the eyes and the distinctness of the numerous lens-facets into 
whicli those special organs are divided. 
There are certain variations in the outlines and form of this, as 
well as of other species of Trilobites, which have been regarded by 
naturalists as sexual characteristics ; judging upon these grounds, 
Mr. Teunant's specimen would be probably considered a female. 
This species, Phacops caudalus, ranges in vertical strati graphical 
distribution from the Lower Llandeilo flags to the Upper Ludlow 
I'ock, and it has also a considerable geographical range. 
The species has been described at length by Burmeister, and also in 
the Decades of the Geological Survey. 
FOREIGN CORRESPONDENCE. 
By Dk. T. L. Phipson of Paris. 
On the Crystalline form of Goal — Coal and Carhiiretted Hydrogen in 
Meteoric Stones — Co(d that cuts Glass like the Diamond — Another 
word on the Artificial formation of Coal. 
I HAVE just published in France some observations " On the Crystalline 
form of Coal."* In November, 1858, I picked up in London some 
fragments of coal that wei-e perfect rhomhohedrons, giving angles of 
102° and 78°. This coal came from Sunderland. In December fol- 
lowing I found many analogous specimens near the town of Glasgow, 
in Scotland, one of which measui-es nearly a foot in evei-y direction. 
The coal-beds near Glasgow have been upheaved by trap-rock, and the 
immense pressure has given to the coal a crystalline structui-e that 
causes it to break imder the hammer in rhombohedric fragments ; 
and these, whatever be their size, give always the same angles, 102° 
and 78°. Graphite, which is known to be a variety of pure carbon, 
is found crystallized in short hexagonal prisms (laminfe), that is, in a 
form derivable from the rhombohedron. Coal and graphite belong 
therefore to the same crystalline system. This fact goes a long way 
to prove that coal must be regarded as a vai-iety of pure carbon, and 
not as a combination of carbon, hydrogen, oxygen, and azote, as some 
have asserted. For the oxygen, hydrogen, and azote that coal gives 
on analysis are derived from the substances, such as bitumen, naphtha, 
vegetable remains, 8ic. with which it is mixed. 
* BMetin de la Soc. Oj Hist. Nat. dc Strasbowrj , aTid Journal dt riiarmacoloyie 
de Briiucellcs. 
