ual times. Thesand glass, Fig. 9,])oetically calledthe hour glass,belongs to thewater-clock classa n d the sa n dflows from onebulb into theother, but it givesno subdivisions ofits period, so ifyou are using onerunning an hourit does not giveyou the half hour.The sand glass is still in use by… … Fig. 9—Modern SandGlass or Hour Glass
Time · Clocks and watches
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