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mouth of the mine is from ios. to 12s. and 14s. per ton, according to the strength of the rock; some being far superior to others. The best yet discovered lay about four feet above the present floor of the mine. About fifty tons of rock arc raised upon an average out of this mine every day; the best of which is sent to Liverpool, and the coarsest thrown into the brine pans to strengthen the liquor of the salt springs, many of which are also found hereabouts, whose produce is boiled and crystallized upon the spot. The mine is ventila- ted by a second shaft. This, however, does not in- troduce a sufficient quantity of air to disperse quickly the sulphurous smoke of the gunpowder produced by the blasts; which hangs about the cavern for a considerable time, and is very sensibly and disagree- ably perceived. The above account, I fancy, gives a tolerably clear idea of all the salt-mines in this neighbourhood; which may vary in their dimen- sions, but little in their appearance or processes. The brine springs are from fifty to one hundred and tvventv feet deep; their liquor in general is fully sa- nitated, producing a prodigious quantity of fine salt; the process of obtaining it is by evaporation as before described, when speaking of Droit wich. The average produce of salt from the mines and pit at Northwich is said to beabout 50,000 tons annual!)
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