Journal - Franklin Institute of the State of Pennsylvania (1826)
Franklin Institute, Philadelphia, Franklin Institute (Philadelphia, Pa.) · [Philadelphia : Franklin Institute] · leaf 100
hrough the hole onceeach month, the plug being replaced after each winding.The clock, therefore, has a double protection against dust,that is, the dust-proof clock room and the dust-proof case. As is common with astronomical clocks, the dial hasthree circles, the minute circle above the center, the… … Fig. 3.—Astronomical clock. 90 Johnson [J. F. I.. left, marked B, is called an auxiliary clock. It is mountedin exactly the same way as the astronomical clock, but is ofmuch cheaper mechanism and is used only in emergencieswhen it would be necessary to oil or otherwise adjust theastronomical clock.…
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