The digitized verisons of a lot of books are interesting. As I've remarked before, the only problem seesm to be that the £$%^&*^$&'s who digitized them didn't always fold out the plates and scan them. Still, what's there is very interesting - and at least they are available. The Open Library is another front end.
Instances:
Machinery for metalliferous mines : a practical treatise for mining engineers, metallurgists and managers of mines
Davies, E. Henry (Edward Henry)
A Text Book of Ore and Stone Mining
C.Le Neve Foster
Westmorland Slates
J.J.Thomas
A Treatise on Slate and Slate Quarrying
David Christopher Davies
Cheers everyone
Grahami
The map is the territory - especially in chain scale.