1823.] 
has lately offered an explanation, which 
bids fair, we think, to set the matter at 
rest. The mines in which the heat has 
been great, and found to increase with 
the depth, are those in which atmospheric 
air is made to descend in great quanti- 
ties, and circulate constantly through the 
workings, before it re-ascend ; and it is 
the condensation which these successive 
portions of air undergo, in descending 
so far below their former station, which 
occasions the evolution of heat, suffi- 
cient, in time, to raise the temperature 
of the adjacent rocks, and the waters 
‘percolating through them into the work- 
ings. We trust mainly to Mr. Moyle, 
for giving to Mr. Miller’s suggestion the 
authority of experiments, sufliciently 
numerous and varied, in the down-cast 
and in the up-cast shafts of the Cornish 
deep mines, to end for ever the idle con- 
troversy alluded to. ’ 
Doctor Hare and Professor SILLIMAN 
pursue with ardour in America, their 
respective experiments on charcoal, on 
uninflammable coal or anthracite, and on 
plumbago, which promise to issue ina 
thorough knowledze of these substances, 
and of their relations to the diamond, 
and the manner of the latter’s formation. 
Plumbago, so soft as to be crushed with 
ease between the thumb and finger, bas, 
by the intense lieat of the deflagrator, 
been melted into globules, vastly harder 
than any kind of glass. 
Tee Caves.—In the mountain of Ro- 
thorn, not far from Thun, Swisserland, 
at an elevation of about 5500 feet above 
the level of the sea, the Schaflock or 
sheep’s-hole cavern is situated, In a grey 
limestone-rock, of great thickness: the 
mouth of this cavern faces the east, and 
is about fifty feet wide and twenty-five 
feet high, ofa rude semi-elliptical shape; 
‘but the dimensions within are much 
greater, and its plansomewhat resembles 
the letter z. In entering this cave on 
the 5th of September, when the sur- 
rounding air stood at 77° of Farenheit, 
M. Durour, after passing the first great 
bend, found that the water dripping from 
the roof was frozen upon the floor, in a 
sheet of solid and transparent zce ; over 
which he and his companions found 
miuch difficulty 1o walk and slide to the 
further end of the cave and back. 
Joun Hawkins Esq. a pupil former- 
ly, and a warm admirer, of the eclebra- 
ted Werner, in an interesting paper pre- 
sented to the Cornwall Geological So- 
ciety, and printed in the second volume 
of its Transactions, on the nomenclature 
of the Cornish rocks, speaking of 
Montuiy Mas. No. 388. 
Spirit of Philosophical Discovery. 
345 
grey-wacke, observes, that the confusion 
and long continued disputes in geologi- 
cal writings, as to this rock, have origi- 
nated from considering it(as M. Wemer 
taught) as a derivative one; that is, as- 
serting it to be composed of the disin- 
tegrated parts and fragments of clay slate 
and others of the primitive rocks; or, 
with Mr. Jameson considering it, as 
commencing a new geognostic, period, 
when mechanical depositions first began 
to succeed those of a erystaline charac- 
ter, exclusively; for, observes Mr. H. 
if this had been the case, nature unques- 
tionably would have Jeft.a bold line of 
distinction between strata, the origin of 
which had been so, essentially different; 
whereas no such line exists, the transi- 
tion, locally, of clay-slate into grey- 
wacke being often insensible; indicating 
“a mode of deposition, both chemical 
and mechanical, without being deriva- 
tive,” to be common to both these rocks; 
a doctrine which, as Mr. H. says, would 
exclude grey-wacke:as a distinct. rock- 
formation, and admit it only as a subor- 
dinate, or locally imbedded one. We 
hail this concession from so zealous a 
geogvost, as the beginning to renounce 
several other unfounded dogmas of the 
same school ; and bope, for the interest 
of useful Geolpaienl Science, that ere 
long the mischievously theoretic terms 
and distinctions of Primitive, Transition, 
Secondary, &c. will be banished from 
geological writings, and be succeeded 
by well-compounded names, expressive 
of the qualities of rocks or strata, ac- 
companied by the mention of their 
actual super-position, and of their sub- 
position also whenever attainable, with 
respect to other defined rocks, in each 
district. of country described: laying 
aside, for the present, all theorizing, uns 
til the habitable globe has, been more 
generally examined. The kéllas of Corn 
wall no-wise differs from the. clay-slate 
of Saxony ; its zronstone fs chiefly horn- 
blend, and its elvan mostly fire-grained 
granite, according to solemn, decisions 
of the Freyburg professor himself, 
Steel.—Amongst the many curious 
and obscure, yet bighly usefal, properties 
of Stec!, one, which has Jong been pri- 
yvately known amongst particular work- 
men, has lately been brought before the 
public, in the monthly “ ‘T'echnical Re- 
pository ;” it is this, that the capacity 
of heated steel to be hardened, on sud- 
denly cooling it, commences at a precise 
point or degree of heat, and increases 
therefrom, accordingly as the heat is in- 
creased, through a certain increasing 
’ 2Y range 
