25a °F 
[April 1, 
PROCEEDINGS OF LEARNED SOCIETIES. 
Eis 
ROYAL SOCIETY OF LONDON. 
. CHEMISTRY. 
NE of the mcft inftruftive and im- 
portant parts of geology, fays Mr. 
Hatchet in his ‘* Obfervations on the 
Change of fome of the proximate Principles 
of Vegetables into Bitursen,” is the ftudy of 
the! pontaneous alterations by which bodies, 
formerly appertaining to the organized 
kimgdoms of nature, have, aiter the lofs 
of the vital principle, become gradualiy 
eonverted into toflil tubftances. In fome 
cafes, this converiicn is fo complete as to 
deftroy all traces of previous organic ar- 
rang-ment; but in others the original 
texture and form have been more or lefs 
preferved, though the fubftances themfelves 
are decidediy mineral. Some of thefe ex- 
traneous foflils retain part of their original 
principles, whilft others can only be re- 
‘garded as cafts or impreffions. Mr. Hatchet 
tele&ts from the animal kingdom, as ex- 
amples, among’ others, the ftoffil ivory, 
which retains its cariilage; the bones in 
the Gibraltar rock, contiting of little more 
than the earthy part or phof{phate of lime. 
The vegetable kingdom has likewife pro- 
duced many ftriking inftances ; and ani- 
mal petrfactions are commonly of a cal. 
careous nature, but vegetable petrifac- 
tions are generally filiceous. 
Mr. Hatch-t’s main object, in this paper, 
is. to adiuce fome proots, that the bitumi- 
nous fubftances are detived from the orga- 
nized kingdoms of nature, and efpecially 
from yegetable bodies. The chemical 
charactets of the pure or unmixed bitumens, 
fuch as naptha, mineral tar, &c. are, in cer- 
tain refpects, fo different from thofe refins 
and other infpiflated juices of recent vege- 
tables, that, had the former never occur- 
red-but in a feparate and unmixed ftate, no 
pofitive inference could have been drawn 
from their properties, in proof of their 
vegetable origin. 
Inftances are produced to thew that foffil 
amimal fubftances torm a feries, com- 
mencing with fuch es are fcarcely different 
from thofe which are recent, and termi- 
nating in productions which have totally 
lo% all traces of organization. 
Similar inftances are afforded by the ve- 
getable kingdom: the three examples 
cited in this paper are, 1. The fubmarine 
foreft at Sutton, on the ceaft of Lincoln- 
fhire, the timber of which has not fuffered 
any very apparent change in its vegetable 
characters: 2. The firata of bituminous 
wood, called Bovey coal, found at Bovey, * 
in Devon; which exhibits a feries of gra- 
dations, from the moft perfeét ligneous 
texture, to a fubftance nearly approaching 
the charaéters of pit-coal, and, on that, 
account, diftinguifhed by the name of 
flone-coal: 3. The varieties of pit-ccal, 
fo abundant in many parts of this country, 
in which almoft every appearance of vege- 
table has been dettroyed. 
Thefe examples appear to form the ex- 
tremities and centre of the feries, but as 
the procefs of carbonization, and formation 
of bitumen, has not taken place in the firlt 
inftance, and as thefe effects have proceed. 
ed to the ultimate degree in the laft, it 
feems moft proper to feck for information, 
and for pofitive evidence, in the fecond 
example, which appears to be the mean 
point, exhibiting effects of natural opera- 
tions, by which bitumen and coal, have 
been imperfectly and partially formed, 
without the ablolute objiteration of the 
original vegetable chara¢iers. 
A confiderable part of this paperis taken 
up in defcribing a remarkable /chiffus © 
found by Sir Jofeph Banks, in the courfe 
of a tour through Iceland, near one of the 
great {pouting {prings. The fingularity 
of this fubftance is, that a great part of it 
confilts of leaves of alder interpofed be. 
tween the different /amelle, in an appa- 
rently half. charred fate, retaining diftinaly 
the form of leaves, and the arrangement of 
the fibres. 
In analyfing 250 grains cf this {chiftus 
the products were as tollow : 
Grains 
Water are ee 
Oily bitumen . . - 7-50 
Mixedioas. «.:pi:) saya 
Charcoal «| ay. ijehi oe Agee 
Silica ote \ dy a 
Oxide of ironscce oy oe 6.00 
Alumina yoo ay siege 
247.00 
But the water and vegetable matter 
being extraneous, the real compofition of 
the {chiftus is filica, alumina, and oxide of 
iron, and therefore it belongs to the family 
of argillaceous fchiftus ; but the propor- 
tion of filica is more confiderable than has 
been found in thofe hitherto fubjeéted to 
cheniical analyfis. Frem this Mr. Hatchet 
was led to examine and analyfe the Bovey — 
coal, found in ftrata, compofed of wood, 
or trunks of trees, which have completely 
loft 
