VOL. VI.] PHILOSOPHICAL TRANSACTIOWS. 571 



makes a mark on his line, by knot or otherwise, and sets his dial down again, 

 and there likewise notes down that point on which the needle stands, at the 

 second position ; and so proceeds from turning to turning, still marking down 

 the points, and his line, till he comes to the intended place ; which performed 

 and exactly set down, he ascends, and begins at the orifice of the adit or work, 

 and repeats above ground what he did in the work ; brings his first knot, or 

 mark in his line, to such a place, as the needle will stand at the same point it did 

 under ground at the knot, and so proceeds till he come exactly over the intended 

 place in the mine. 



But to return to the water, if this conveniency of an adit may be had, then 

 our water annoys us but a little, as long as we keep on that level with the 

 adit ; for we drive not always on one and the same level : As for instance ; at 

 five fathoms we make a drift both ways, and sinking five fathoms more, we 

 make another drift at ten fathoms, and as deep as we please. Now when 

 we once pass that level on which our adit runs, and the water begins to trou- 

 ble us, we have this remedy ; either with a winder and keebles, or leathern 

 bags, pumps, or buckets to get it up to the adit level, and so we are forced to 

 do to the very top, where we have not the convenience of an adit, as in plains. 

 Some, but very few works may be dry. 



We observe, that if we have water we never want air sufficient for respiration, 

 and our candles to burn in; but yet this caution must be annexed, that in a soft 

 loose quagmire clayey country, by the falling of the deads after us, yet not in 

 such measure as totally to stop us up, although we have water, yet our air is ra- 

 ther too copious, or so much condensed, as that it becomes in a manner a damp, 

 and requires an air-shaft for vent, which damps are sometimes enlarged by work- 

 ing of the mundic with the ore. 



In case the country be not strong enough (as being over-soaked with water 

 from above) to support its own weight, we under-prop our drifts with stemples, 

 and wall plates, placed much like a carpenter's square, on the one side and 

 over head. 



The Manner and Way of Dressing Tin. 



After the ore is landed, and the greater stones broken at the top of the mine 

 by the shovelmen, it is brought on horses to the stamping or knocking mills, 

 and unloaded at the head of the pass (i. e. two or three bottom boards with two 

 side boards sloping\vise) in which the ore slides down into the coffer; but that 

 it may not tumble down all at once, there is placed a hatch nigh the lower end 

 of the pass (i.e. a thwart board to keep up the ore) beneath that comes in the 

 cock water in a trough cut in a long pole, which with the ores fall down into 



4 c 2 



