ciation, has made some experiments in the comparatively shallow salt mines of Cheshire which evince an augmentation of 1° in 70 feet from the surface.
But the greatest strength of observation, independent of mineral veins, has been concentrated in the coal districts. Mr. Bald, Mr. Buddie, and other observers, have long since collected much information in the collieries of the Tyne and Wear; of which, however, we can make only partial use, because the experiments were mostly made on the air, which, for many reasons besides miners' lights and chemical actions, is unlikely to yield accurate ratios, such as are now attainable.
The following are some of Mr. Bald's results, published in the Edinburgh Royal Transactions. The scale is Fahrenheit's.
Whitehaven.—Spring at surface 49°
480 feet 60
Ratio from surface, 1 for 44 feet.
Workington.—Spring at surface 48°
504 feet 60
Ratio from surface, 1° for 42 feet.
Percy Main Colliery, Northumberland.—Mean
temperature at surface 49°[1]
900 feet depth 70
Ratio from surface, 1 for 43 feet.
Jarrow colliery.—Surface assumed 49.5°
Water at 882 feet 68.0
Ratio from surface, 1 for 48 feet.
Killingworth colliery.—Surface assumed 48°
Water at 1200 feet depth 74
Ratio from surface, 1° for 46 feet.
The near accordance of these results is remarkable. The ratios are all in error by a small quantity, because HO allowance is made for the depth of variable heat.
- ↑ It is really under 48°.—Author.
