On a High Sensitive Water Tube Tiltmeter and its Application to the Earth Tides.

Abstract

In this paper, a water tube tiltmeter is newly designed to observe the earth tides by the method of mechanical magnification. The magnifying device is shown in Fig. 1. The mechanism of the device is similar to that of the vertical extensometer of sagging wire and bifilar suspension type: i. e. the vertical motion of the float (7) is transformed into the horizontal motion of two light alminum bars (4) of 2 gr. weight. This motion is transformed into the deflection of the reflecting mirror (6) by the bifilar suspension (5) of phosphor bronze strips. The sensitivity of the device is, with optical distance of 2.5 m., about 0.08/2 of water level change per mm. on the record. This is sensitive enough to observe the earth tides, using water tube of 10 m. long. In Fig. 3 is shown an example of a tiltgram observed at Osakayama Observatory. The records are tentatively analyzed.