Watercolour by John Nixon, showing Lord Penrhyn's slate quarry near Bangor. The painting is signed with initials and dated 1807, but on reverse is dated 1808 and inscribed 'obverse to reduce the distant figures at the end of the quarry - they are too large'. Slate has been mined here since the 16th century and is still used as a roofing material. At the start of the 21st century this slate quarry was still the largest in the world and being used.
© Science Museum / Science & Society Picture Library