Hydrostatic level instrument

Claim 1

A hydrostatic level instrument, comprising: a liquid containing reservoir having a transparent side wall, said reservoir being generally elongated and having a uniform internal cross section, said side wall having a fixed graduated scale including uniformly spaced indicia increasing above and below a zero mark; a level including an elongated rod including a web and a pair of spaced flanges, one on each of the ends of said web, and being generally in the form of an "I" in cross section; said rod having at least one fixed scale including indicia directly measuring distances above a zero point at the bottom thereof; a transparent tube mounted on the web within the space between said flanges, said tube being flat and rectangular in transverse cross section with the sides thereof in contiguous relation with each other, said tube extending across the major width of said web; and a pair of movable tapes mounted for longitudinal movement, at least one of said tapes being movable over the face of said tube, each of said tapes having a scale including indicia increasing above and below a zero indicia thereon, said movable tapes being endless and mounted for movement within said flanges with the loops of the tapes passing over both sides of said web; a guide, means mounting said guide for longitudinal movement along said rod; and a flexible duct interconnecting the lower ends of said reservoir and said transparent tube.