180 Scientific Intelligence—G eology. 
and not upon any accurate and detailed statistical accounts, such as alone 
could warrant a confident opinion. This question will, ere long, become 
a subject of serious concern, unless some measures are taken to found 
our calculations on a solid basis. It is an easy matter to assume that a 
considerable thickness of available coal extends over hundreds of square 
miles ; but the different opinions formed by men of the highest respecta- 
bility and talent, strongly prove how meagre and unsatisfactory are the 
only data on which their estimates are founded. It is not, however, the 
mere quantity of coal that is to be considered; especial regard must be 
had to its quality, depth, thickness, extent, and position, Many of the 
inferior seams can only be worked in conjunction with those which, by 
their superior quality, repay the expense of workingt hem at depths vary- 
ing from 300 to 600 yards; and it may readily be conceived that infe- 
rior coal only could not be profitably raised from pits equal in depth to three 
or four times the height of St Paul’s cathedral, unless the price of such 
inferior coal was raised to more than the present price of the best coal, 
It is the additional expense, and consequent additional difficulty, of com- 
peting with other countries, that is the vital question to be considered, It 
is not the exhaustion of mines, but the period at which they can be pro- 
fitably worked, that merits earnest and immediate attention; and it is 
with especial reference to this that the value and increasing necessity for 
mining plans is so strongly apparent. If these inferior seams are not 
worked now, in conjunction with the better seams, they will, in all pro- 
bability, be wholly lost; and, to a certainty, they must be so, if no per- 
manent registration is adopted to show what were the former circum- 
stances of each mine.—7', Sopwith, on the National Importance of pre- 
serving Mining Records. 
7. Eruption of Boiling- Water from the extinct Volcano of Solfatara. 
—From Naples, we lcarn, that the famous extinct voleano of Solfatara, 
near Puzzuoli, the last eruption of which took place in 1198, and which, 
in 1507, according to the writers of the time, threw up immense quanti- 
ties of boilins water, has, for a few days preceding the date of the com- 
munication, repeated that phenomena, the same having been preceded by 
an emission of hot sulphureous vapour. The thermal water ejected is 
thrown from the eastern portion of the crater at intervals, and in the 
form of jets, from 15 to 20 feet in height.— Atheneum, No. 892, p. 1100. 
8. Temperature of the Mediterranean.—M. Aimé has addressed to the 
Academy of Sciences of Paris some observations on the temperature of 
the Mediterranean Sea, of which the following, according to him, are the 
results :— 
1. Near the shores of the Mediterranean, the temperature at the sur- 
face of the sea is notably higher than at a distance from land during the 
day, and sometimes lower during the night. Near the shores of the 
ocean, the temperature at the surface of the sea is lower than at a dis- 
tance from land, 
2: The mean temperature of the year at the surface is nearly the same 
as that of the air. 
3. The diurnal variation of the temperature ceases to be sensible at 
16 or 18 yards, and the annual variation at 300 or 400 yards. 
4. In the morning, after a clear and calm night, the temperaturaof 
the surface is colder than that of the layers situated some yards below it. 
