REMOTE-READING MICROMETERS; AN APPARATUS, CONSISTING OF A TANK GAUGER'S REEL AND TAPE WITH A METAL PLUMB BOB AND A MILLIAMMETER IN THE CIRCUIT THROUGH THE PLUMB BOB AND TANK SO THAT THE MILLIAMMETER DEFLECTS WHEN THE PLUMB BOB PASSES THROUGH THE LINE OF DEMARCATION BETWEEN THE OIL AND THE WATER IN THE TANK AND USED FOR INDICATING SAID LINE; SPECIFIC GRAVITY METERS, AND VOLUME MEASURING APPARATUS-NAMELY, AN ACOUSTIC RESONATOR FOR A CAVITY TO BE MEASURED AND ELECTRICAL APPARATUS FOR MEASURING THE RESULTING RESONANT GREQUENCY WHICH IS A MEASURE OF THE CAVITY VOLUME