I too think these photographs are from the 1890's. The two furnaces don't look as if they have been in fire for sometime. Maybe not since 1877. The site was apparently bought for the slag heaps. A slag crushing machine was brought in and the slag removed by rail (for roadbuilding?) Perhaps these photographs show that phase.

Industrial History of Dean by Cyril Hart should be available through the Library system. I must have taken it out from a Hampshire library.

Roger