228 Mr. M. Dunn on the Sinking of Preston Grange Engine Pit. 



Bald and Grieve on this subject, I agree in opinion with those gentlemen, who, from 

 their professional department, are so well qualified to judge of this branch of engineering. 



Recollecting, however, of having seen a somewhat similar operation in progress near 

 Glasgow, by a Mr. Nimmo, I believe, it occurs to me, that as this must be well known to 

 Mr. Bald, it would therefore be obliging and useful to the Society of Arts, if he would 

 give some brief account of that operation, along with the Report of this Committee. 



(Signed) ROBERT STEVENSON. 



The addendum by Mr. Bald regarding the Tubbiug used by Mr. Nimmo, need not be 

 here copied, as it appears to be of a different kind, and for a different purpose. 



J. T., Sec. 



The chief object of the present speculation was the Preston Grange 

 Great Seam, varying from 7 to 9 feet in thickness, and dipping in a 

 direction nearly west from the old crop workings towards the Harbour 

 of Morrison's Haven, within 150 yards of which the present winning 

 has been effected.* 



The upper part of the colliery was won in ancient times by a day 

 level drift.t which commenced at high water of the Frith of Forth, and 

 cut the great seam 11 fathoms below the surface, at the distance of 

 500 yards. 



Not only the Great Seam, but several under seams, commanded by 

 this level, were wrought away, until the failure of the level, and a va- 

 riety of other adverse causes, induced the abandonment of the colliery, 

 in the year 1746 ; and, although the antient level still discharges about 

 200 gallons of water per minute, it is well understood that a considerable 

 altitude remains stagnant in the old workings. 



The old people projected a winning near to the present one, and sup- 

 posed the Coal to lie there at the depth of 50 fathoms, but the uncertainty 

 of that conclusion, the difficulties to be anticipated in sinking, and, above 

 all, the probability of the water from this and other adjoining wastes 

 being communicated by the fissures of the Stone and Coal, which, in 

 the opinion of most professional persons who had examined the pro- 

 perty, was extremely probable, had hitherto deterred any one from at- 

 tempting it. 



* See Plate iv. f See Plate iv. 



