Examine the scene in detail. The man on the right crouched down behind the tripod is a diler or surveyor presumably looking along the tunnel the men where the men are. The man on the left is holding a safety lamp to provide him with light to work with. The man back right looks incredibly bored by the proceedings. There are more people around the scene than would be normal. Again, a major challenge for our unknown photographer. The term diler comes from a method of surveying using a dial.