The Cathedral, Marston Salt Mine, Northwich, Cheshire, England, 19th century
The Cathedral, Marston Salt Mine, Northwich, Cheshire, England, showing the pillars of salt that have been left to support the ceiling of the cavern which has been left after the excavation of rock
Nitroglycerin processing plant, explosives factory, Val Bormida, near Cengio, Italy, 1888
Nitroglycerin processing plant, explosives factory, Val Bormida, near Cengio, north-west Italy, 1888. Nitroglycerin was mixed with Kieselghur (a diatomaceous earth) to produce Dynamite