Development is the process of mining the tunnels underground to reach and follow the lode.
From the main shaft horizontal tunnels were driven outwards to meet the lodes. These tunnels were known as crosscuts. When a crosscut met a lode, a tunnel was then driven to follow the lode. These tunnels are known as ‘drives’ whilst being developed and ‘levels’ when completed. Each level was driven at intervals of approximately 100 ft (30m) apart vertically. The drives would be wide enough to allow men and machinery to pass safely. At Geevor the levels are usually 2.4 metres wide and 2.1 metres high.
Two machine men or developers worked together to drill a pattern of holes into the face of the tunnel. The holes were then charged with blasting gelatine - a powerful explosive - and fired with electric detonators. A normal round of explosives can break nearly 20 tons of rock. Blasting was carried out at the end of the working day to allow time for the poisonous gases produced from the blast to be removed from the mine by the mine’s ventilation system before the miners began work the next morning. The following day the broken rock was removed using a mechanical shovel. This was called ‘mucking out’. After the tunnel was cleared the process would begin again. Using this method, tunnels could be advanced at a rate of about 2.4 metres (8 feet) per day.
Advancing the tunnels
Compressed air and water, fed in through pipes, were needed for drilling. Tramming track and ventilation tubing, known as bagging, was also required. As the tunnels were advanced, all of this equipment was extended by the developers.
Photograph reproduced with the kind permission of the David Wills Collection held by the Geevor Archive