. Scientific American Volume 85 Number 01 (July 1901) . f^ i. ffi The aggregate tonnage of American vessels Is5,164,839 tons, and the vessels having a tonnage of1,565,587 navigate the Great Lakes. The aggregatetonnage ten years ago, or In 1891, was 4,684,759. Kg. 2.—HEW PYEOMETEB. In the chamber, G, partly filled with water and inwhich plunges the tube, n n. If the vacuum Is greaterthan the water pressure, this will allow air to enterthrough the tube and the vacuum will be diminished.In practice a small quantity of air always passes luthe tube and the vacuum is kept constant. To main-tain a co
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