LEAP YEAR. 



the contemporary annalists, dates varying not only in different 

 countries according to their different usages, but even in the same 

 country in different ages, have been changed into those dates 

 which they would have had if the Julian chronology had prevailed 

 then. 



It is evident that without this simplification and assimilation, 

 historical dates would present a mass of confusion, which would be 

 inextricable to all ordinary readers. 



92. It has been already stated that the interval of 365| days, 

 assumed in the Julian reformation as the length of a year, is not 

 its true length, but differs from it by a very small fraction of a 

 day. As we have now to explain the part which this very 

 minute fraction has played in chronology, it will be necessary to 

 convey to the reader a more clear and distinct notion of the 

 meaning of the word year, than that which is included in the 

 general statement that a year is the period after which the seasons 

 are reproduced ; for it may fairly be asked what determines the 

 limits of the seasons ? how are the exact moments of time at 

 which they severally begin or end defined ? For it must be observed 

 that our enquiries now involving not whole numbers of days, but 

 small fractions of a day, it is not enough to know that this or that 

 season begins or ends on this or that day; we must know the 

 hour, minute, second, nay even the fraction of a second, which 

 marks the epoch we desire to determine. 



It is customary then to define the course of the seasons by the 

 moment at which spring begins. It has been agreed to take for 

 this the moment at which the centre of the sun's disc has such a 

 position in the heavens, that if it were stationary there, day and 

 night would be exactly equal, that the sun would be in short 

 exactly twelve hours visible, and twelve hours invisible : twelve 

 hours above, and twelve hours below the horizon. 



It may be said that this definition is needlessly verbose and 

 complex, inasmuch as it would be more simple and intelligible to 

 say at once that spring begins on the day of the equinox. 

 ' Undoubtedly such a summary statement would be much 

 shorter and more simple, and provided that it be clearly under- 

 stood, and that it be sufficiently definite, it can be subject to no 

 objection. But what is meant by the " day of the equinox?" 

 We shall, of course, be answered that it is that day on which the 

 sun is twelve hours above, and twelve hours below the horizon. 



Yery well ! let us go to the almanac, and search for such a 

 day. We take the almanac of 1854, and find that on 19th 

 March the sun was twelve hours and one minute above, and 

 eleven hours and fifty-nine minutes below the horizon. On the 

 20th it was twelve hours and six minutes above, and eleven hours 



165 



