^6 Of the Under-ground inclined Tlan6 



width is feven feet four inches. It ttiov^s upon four folic! 

 caft- iron rollers, which run upon caft-iron plates ; on one 

 iide of each of which there are iron crefts, which (land two 

 inches higher than the plates, arid prevent the carriage from 

 running off the road. 



The weight of neat coal, contained in the loaded boat, is 

 about twelve tons : the boat weighs about four tons ; and 

 the carriage, or cradle, in which the boat is placed, when 

 conveyed down the inclined plane, is about five tons : — in all 

 about twenty-one tons. 



At this inchned plane, thirty loaded boats are now let 

 down, with eafe, in about eight hours; that is to fay, four 

 boats are let down in a little more than an hour. The boats 

 ufed in thcfe collieries are of different fizcs and dimenfions ; 

 fome will carry feven, forrie eight and a half, fome twelve 

 tons. 



The weight of neat coal, independently of the weight of the 

 carriage and boat's, which is let down the inclined plane, in 

 twelve-ton Ijoats, in eight hours, will confequently be three 

 hundred and fixty tons. The weight of the carriage, fuppofe 

 five tons, let down in the fame time, will .be one hundred and 

 fifty tons ; and the weight of the boat, fuppofe four tons, thirty 

 times down, in eight hours, w^ill be one hundred and twenty 

 tons :— in a]l fix hundred ^ri4 thirty tons dovvn in eight 

 hours. 



The weight of the carriage thirty times up, and thirty 

 boats up, in eight hours, will be 

 Carriage, at 5 tons, 30 times up = 150 tons 

 Boat, at 4 tons, 30 times up = 120 tons 



In all 270 tons up in eight 

 hours. 

 So that there will be 630 tons down 

 %*]0 tons up 



In all 900 tons moved at the inclined plane, 

 in 8 hours, exolufive of an indeter- 

 minate quantity of materials occa- 

 fionally brought up for the ufe of 

 tlie higher level collieries. 



