This functional instrument consist of a silvered metal bellow with at least 12 seperate chambers. It is attached to a recoding pen via a complex linkage which allows the barometric reading to be traced on a revolving drum. The brass drum, overlaid by a chart paper, is driven by an internal, high quality clock work which turns the drum precisely once a week. The paper encircling the drum is divided by hours and days of the weeki. So calibrated, the graph records barometer pressure for any given hour of the day over a week long period. The entire mechanism is housed in its equally solid mahogany case, glazed on 3 sides and hinged on one end with double brass hook closure on the other and a very nice folding brass handle on the top.