Professor Jameson on the Black-Lead of Glenstrathfarrar, 
mined. The working is carried on by ten or twelve men, and 
is entirely at the day, the miners not having sunk more than a 
few yards from the surface. The quantity hitherto raised has 
been inconsiderable ; last year, for instance, the quantity sent to 
the London market did not exceed hve tons. This was sold 
at the rate of L. 93 per ton, thus affording a great profit to the 
proprietor, as the average expence of mining and transport did 
not exceed L. 13 a ton. 
A road is now cutting from the mine to the high road, which, 
when finislied,, will enable the proprietor to work this valuable 
repository of black-lead in a more extensive manner than is 
done at present. 
We have little doubt that graphite will be detected in Glen- 
strathfarrar, in much larger masses than those we have already 
described, and that ere long, if the mining is carried on with 
judgment and activity, this part of Scotland will afford a con- 
'siderable supply of this mineral. 
Art. XXVI.— the Temperature of Air and of Water in 
the Coal Mines of Great Britain, particidarly in those which 
are of the greatest depth^. By Robert Bald, E.R.S. E,. 
G. S. ^md M. W. S, Coinmuihcated by the Author. 
The increase of temperature in coal mines, is a fact familiar 
to every person who has had occasion to frequent them. The 
instant a dip-pit is connected with a rise-pit by a mine, a strong 
circulation of air like wind commences. If the air at the sur- 
face is at the freezing point, it descends the dip or deepest pit, 
freezes all the water upon the sides of the pit, and even forms 
icicles upon the roof of the coal within the mine ; but the same 
air, in its passage through the mines to the rise-pit, which is 
generally of less depth, has its temperature greatly increased, 
and issues from the pit mouth in the form of a dense misty 
This article is a brief abstract of a paper which was read before the Epyal 
Society of Ediaburghj on the 5th April 1810. - 
