Hartley Colliery disaster: Two hundred and four men and boys killed in a mining disaster, prompting a change in UK law which henceforth required all collieries to have at least two independent means of escape.

The Hartley Colliery disaster was a coal mining accident in Northumberland, England, that occurred on 16 January 1862 and resulted in the deaths of 204 men and children. The beam of the pit's pumping engine broke and fell down the shaft, trapping the men below. The disaster prompted a change in…