English: The Arsenic Labyrinth at Botallack Mine Arsenic compounds were an unwanted pollutant in tin ore which ruined the smelting process. The solution was to heat the ore to drive off the arsenic as a vapour. In the early days of mining this badly polluted the surrounding countryside. However arsenic itself proved to be a saleable by-product so the arsenic fumes were sent through a labyrinth of tunnels where it would condense on the tunnel walls. This photo shows part of the arsenic labyrinth at Botallack mine. The maze of tunnels has partially collapsed. Half way through the labyrinth, the tunnel passes over the top of an arch to cross one of the entrances to the mine. At the end of the labyrinth the remaining fumes passed up the tall chimney shown in the photograph.