. Time and its measurement . :46 12:13 July :04 :47 Feb 12:14 :05 :48 12:13 12:00 Dec. :49 Mar 12:12 Aug. :05 :50 12:11 :04 :51 12:10 :03 :52 12:09 :02 tt :53 12:08 :01 :54 12 :07 :00 :55 5 12:06 Sept :59 :56 28.! 12:05 :58 :57 Apr 12-W :57 :58 12 :0:! :56 :59 7 12:02 :55 :00 12:01 :54 :01 12:00 :.53 :02 !!».. 11:5!) :.5
. Time and its measurement . :46 12:13 July :04 :47 Feb 12:14 :05 :48 12:13 12:00 Dec. :49 Mar 12:12 Aug. :05 :50 12:11 :04 :51 12:10 :03 :52 12:09 :02 tt :53 12:08 :01 :54 12 :07 :00 :55 5 12:06 Sept :59 :56 28.! 12:05 :58 :57 Apr 12-W :57 :58 12 :0:! :56 :59 7 12:02 :55 :00 12:01 :54 :01 12:00 :.53 :02 !!».. 11:5!) :.52 12:03 24. 11:.58 :51 The above table shows the variation of the sun from meanor clock time, by even minutes. the same place in its elliptical orbitand the correction of this by the leapyears causes the equation table to varyin periods of four years. The centen-nial leap years cause another variationof 400 years, etc., but these variationsare less than the error in reading a dial. 18 TIME AND ITS MEASUREMENT. zontal Sundial for-43 The reason that the table given hereis convenient for setting clocks to meantime is that a minute is as close as adial can be read, but if you wish forgreater accuracy, then the almanac,which gives the equation of time toa second for each day,.will be reason that these noon-mark dialsare better than ordinary commercialdials is that they are larger, and stillfurther, noon is the only time that anydial is accurate to sun time. This is be-cause the suns rays are refracted ina variable manner by our atmosphere,but at noon this refraction takes placeon a north and south line, and as thatis our noon-mark line the dial reads
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Keywords: ., boo, bookcentury1900, bookdecade1900, booksubjectclocksandwatches
