Geographisches Zeitmessinstrument

1,084,875. Clocks. KILBURG GEOCHRON CORPORATION. April 23, 1965 [April 27, 1964], No. 17185/65 Heading G3T. A geographical clock as described in Specification 1, 050, 178 which uses a map of the globe, includes means moving constantly and continuously to delineate and visibly distinguish the areas experiencing day and night, along with means to cause rectilinear movement of the map relative to the delineating means to visibly represent the changing position of day resulting from earth rotation. The curved line 21 shows the areas at the winter solstice in the northern hemisphere. This changes to the straight lines 22 for the vernal equinox and thence to the reverse curve 24 for the summer solstice. Two flexible blades (26), Figs. 2-20 (not shown) are caused by a driving system to oscillate about central pivots and also to flex so as to form the gradually changing line of delineation. An arrangement of pivoted light filters 33, 34, 36 connected with the driving system, forms the night area, illuminated from behind so as to be in shadow without being obscured for reading purposes. To take account of the ecliptic which creates apparent time as distinguished from mean time, the driving system includes means for oscillating the delineation as required in the direction of the equator. To this end the reeds and filters are mounted on a movable plate 68, Fig. 7 (not shown) oscillated by a cam (45). The sun at zenith is indicated by a crossshaped member 85a which shows behind the translucent map. This member is movable automatically by the drive mechanism, Fig. 2 (not shown). An adjustable latitude scale 100 is provided, along with a scale 102 whereby the equation of time and the sun meridian passage may be read by comparison of the position of the sun mark and the mean hour 12. In a modification, Figs. 18-19 (not shown) this latter scale is adjustable longitudinally to give a direct reading. The hour angle of the sun either apparent or mean and either with reference to Greenwich or any other location, is read from an hour angle scale (110). Manual adjusting means (118, 119) Fig. 2 (not shown) is arranged to over-ride the automatic drive system, so that the device may be turned to any point in time for reading and restored to present time to resume automatic operation. An automatic indicator (78) showing the seasons and zodiacal signs is provided. The date to left and right of the international date line is indicated on a tape showing at window 75.