In the 1880's, Katahdin Iron Works centered on a stone furnace enclosed within buildings that handled each step of iron making. Raw iron ore was prepared in the Ore Kiln, dumped into the furnace through the Top Houses, and superheated by burning wood charcoal produced in brick kilns. Mixing the ore with limestone caused a chemical reaction that produced molten iron, which flowed from the bottom of the furnace into the Casting Shed. There, men formed sand molds and channels on the floor, and the liquid iron filled them to make pig iron bars that were cooled and sent to market by train. By the 1880's, a steam locomotive could pick up the bars outside the casting shed and carry them to Bangor for shipment by ship to purchasers. A large Storage Barn held equipment and replacement parts needed to keep the operation running, and on return trips the train could bring passengers and supplies, including shingles and a new batteau boat. The batteau was the basic means of transportation for men working on the lakes and rivers of northern Maine, especially in the lumbering industry.