Iron. 
the expence at which it could be procured by a different 
mode of operation. It therefore becomes necessary to 
make perforations by means of horizontal galleries, extend- 
ed under the soil, so as to fall in with the declivity of the 
strata : these catch the inclining stone for a stretch of 
100 to 240 yards, according to the existent circumstan- 
ces of the mine, 
* / 
These galleries are in Scotland called the barrow roads. 
Whenever the miner has arrived at the extremity of his 
working, he turns round and commences an excavation 
on his right and left hand, proportioned to the rise and dip 
of the stone, to the extent of several yards on each ; the 
accompanying shist and rubbish are packed into the va- 
cuity behind him : should there remain any superfluity 
unpacked, it is wheeled to the mouth of the gallery along 
with the iron-stone. In this manner the miner returns* 
and brings along with him the whole iron-stone contained 
in 100 to 240 yards in length, and in 20 to 30 yards in 
width. The height of the gallery is commonly so small, 
that the miner is obliged to perform his work upon his 
side \ the wheelers are likewise obliged to push the bar- 
row on all fours. This species of working is called under 
cover $ and the attainment of a band of good iron-stone* 
though only four inches thick, will sufficiently defray the 
ex pence of the operation. It is here also obvious, that 
this operation can only be carried a certain length in the 
same gallery, till such time as the expence of wheeling out 
the stone must exceed the value of that share of labour 
generally appropriated to it* A more economical method 
is therefore indispensibly requisite. This is effected by 
sinking a pit 160 to 200 yards farther on the same line of 
level. When the iron-stone is found, the miner sets off" 
another gallery, or barrow road, towards his former work- 
ing, and continues till he meets the termination of his old 
waste: as formerly, he now begins his retreat, and carrier 
