Belgium:--

Metres. Ft.
Saint Henriette, Cie des Produits, Flenu, Belgium 1150 3773
Viviers Gilly " 1143 3750
Marcinelle, No. 11, Charleroi " 1075 3527
Marchienne, No. 2 " " 1065 3494
Agrappe, Mons " 1060 3478
Pendleton dip workings Lancashire 1059 3474
Sacre Madame, Charleroi Belgium 1055 3461
Ashton Moss dip workings Lancashire 1024 3360
Ronchamp, No. 11 pit France 1015 3330
Viernoy, Anderlues Belgium 1006 3301
Astley Pit, Dukinfield, dip workings Cheshire 960 3150
Saint Andre, Poirier, Charleroi Belgium 950 3117

The greatest depth attained in the Westphalian coal is at East
Recklinghausen, where there are two shafts 841 metres (2759 ft.) deep.

The subject of the limiting depth of working has been very fully studied
in Belgium by Professor Simon Stassart of Mons ("Les Conditions
d'exploitation a grande profondeur en Belgique," _Bulletin de la Societe
de l'Industrie minerale_, 3 ser., vol. xiv.), who finds that no special
difficulty has been met with in workings above 1100 metres deep from
increased temperature or atmospheric pressure. The extreme temperatures
in the working faces at 1150 metres were 79 deg. and 86 deg. F., and the
maximum in the end of a drift, 100 deg.; and these were quite bearable
on account of the energetic ventilation maintained, and the dryness of
the air. The yield per man on the working faces was 4.5 tons, and for
the whole of the working force underground, 0.846 tons, which is not
less than that realized in shallower mines. From the experience of such
workings it is considered that 1500 metres would be a possible workable
depth, the rock temperature being 132 deg., and those of the intake and
return galleries, 92 deg. and 108 deg. respectively. Under such
conditions work would be practically impossible except with very
energetic ventilation and dry air. It would be scarcely possible to
circulate more than 120,000 to 130,000 cub. ft. per minute under such
conditions, and the number of working places would thus be restricted,
and consequently the output reduced to about 500 tons per shift of 10
hours, which could be raised