488 Duke ofBridgewatet^s underground inclined Plane. 



The place where the inclined plane is conftruded, is adapted in a fingular way for the 

 purpofe. There is a bed of white rock, or grit, eight yards twelve inches deep, which dips 

 one in four, lying exaftly in the direftion moft convenient for the communication between 

 the two levels ; which bed of rock is hollowed into a tunnel, driven upon the rife of the 

 metals, by blading with gunpowder, and working it down with wedges and hammers. In 

 this tunnel, formed through a rock reaching from the lower to the higher level, the in- 

 clined plane is fixed ; and, by its being in the heart of a rock, the whole workmanfliip 

 can be pinned, fecured, and compared together at the top, bottom, and fides, moft ef- 

 fedtually: — an advantage which no inclined plane above-ground can have, and which ren- 

 ders this a fingular produ£l;ion, no where perhaps to be imitated. 



The run of the inclined plane is one hundred and fifty-one yards, befides eighteen yards, 

 the length of the locks, at the north or upper end : and the fall is one in four, correfpond- 

 ing with the dip of the rock. 



Of thefe one hundred and fifty-one yards, about ninety-four yards are formed into a 

 double waggon- Way, in order to let two boats, namely, the empty and the loaded boat, 

 pafs up and down ; and are divided by a brick wall, fupporting the roof, in which are 

 openings for a perfon to efcape out of the way of the boats ; which double-waggon way 

 joins in one, about fifty-feven yards from the lower level. 



The whole width of the double waggon-way is nineteen feet ; and of the fingle waggon- 

 way, after the jun£tion, ten feet. 



Thefe waggon-ways arc fupplied with iron rails, or gullies, laid on fleepers, down the 

 whole run ; and the height of the roof, above the iron rails, is eight feet. 



At the top of the inclined plane there is a double lock, or rather two locks, fide by fide, 

 formed in the heart of the fame rock, which deliver the loaded boats from the higher level 

 down the inclined plane, and receive the empty boats from the lower. The length of that 

 part of the tunnel in which thefe are formed, is eighteen yards; the width or diameter, 

 twenty feet fix inches; and the height of the roof, at the north end and above the locks, 

 zx. d d, Plate XXI. Fig. I. twenty-one feet, to admit the break-wheel. 



The bottom, or fouth end of the inclined plane, is fix feet nine inches under the furface 

 of the water, where the loaded boat floats oft" the carriage upon the canal of the lower level. 



The depth of the locks, underwater, at the north end, is four feet fix inches; at the 

 fouth end it is eight feet. 



The wall between the locks is nine inches above the furface of the level water ; its 

 breadth is three feet. 



The diameter of the horizontal main (haft, upon which the rope works to let the loaded 

 boats down, and to draw the empty boats up, is four feet eleven inches, and its circum- 

 ference is fifteen feet five inches. The main-rope is two inches and a half in diameter, 

 and feven inches and a half in circumference. It is lapped round with a fmall cord of 

 about an inch in circumference, for the length of about one hundred and five yards, to 

 prevent its wearing, which it does chiefly when it drags upon the bottom, when at work, 



at 



