222 BERTHA'S VISIT TO HER 



sawed first, and afterwards "split in the usual 

 manner. Here also, we saw an immense number 

 of little writing-slates ; they are made from the 

 finest grained part of the quarry ; and their 

 smooth surface is produced by an operation very 

 like that of planing a board. 



The great blocks are carried from the quarry to 

 the mill, and the slates, when dressed and finished, 

 are also conveyed to the sea-side, by little waggons 

 on iron railways. It is wonderful what a load a 

 horse will draw in this manner when compared with 

 the utmost work he can do on the best common 

 road ; and yet a railway appears to be a very 

 simple contrivance. Two parallel lines of flat 

 iron bars are laid along the road 5 the horse walks 

 between them, and thus the wheels of the waggon 

 in rolling along the bars, neither meet with the 

 stones and obstacles which would impede their 

 motion on a road, nor do they sink into its hol- 

 lows, and soft places. The bars are scarcely 

 broader than the rim of the wheels, which would, 

 therefore, slip off, but for a little raised ledge, or, 

 as it is called a flange, along one edge of each 

 bar. When railways are intended to carry 

 heavy weights, both going and coming, they must 

 be laid perfectly level : but at these quarries, as 

 all the weight goes down to the Port for embark- 

 ation, the same horse that draws several loaded 

 waggons hooked together down hill, can re- 

 turn up hill with an equal number of empty ones. 



