This is the barograph by Barigo, makers of the world's finest, most precise meteorological instruments since 1926, and is the same one preferred by art museums for its accuracy in detecting changes in temperature and humidity, key to the preservation of priceless works of art. Meticulously hand-crafted by engineers from Germany's clock and precision instrument development region located in the Black Forest, this device uses eight aneroid capsules each made from two .0002" thick sheets of copper/beryllium alloy electron-welded together for an exact fit. Atmospheric pressure changes cause the capsules to expand or contract, and the gold plated tool steel linkages amplify the capsules' changes into movements of a stylus, which inscribes barometric pressure onto a graph affixed to a rotating cylinder. The cylinder is precisely calibrated using quartz watch movement, and provides an accurate eight-day history of pressure trends--the drum may be removed after eight days to replace the paper graph (one year's supply included). The barograph is housed in a mahogany case with glass panels. Requires one AA battery for the cylinder. (8 1/2 lbs.)