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Show Mini)' Kinds uf Ihtyn In Our. A mean solar day is the average or mean of all the apparent solar d:iys in a year. .Mean solar time is that shown by a well regulated clock or watch, while apparent solar time is that shown by a well constructed siui dial. The difference differ-ence between the two at any time is the equation of time, and may amount to sixteen minutes ami twenty-one second:;. sec-ond:;. The astronomical day begins at noon and the civil day at the. preceding midnight. The sidereal and mean solar so-lar days are both invariable, but one day of the latter is eiia! to one day three minutes and jij.fiof. seconds of the former. |