of places have remained the same from the 

 earliest time of observation. Indeed, we can 

 see no cause why there should, or even 

 could, be any variation in this particular 

 motion of the earth. The influences of the 

 other celestial bodies, in as far as they tell 

 upon the earth at all, tell upon the whole of 

 it as one entire mass, of which the whole of 

 the parts are alike affected, in the ratios of 

 the squares of their distances from the dis- 

 turbing sun, moon, or planet ; and, therefore, 

 the distant bodies in the heavens no more 

 disturb the rotation of the earth on its axis, 

 than they disturb the going of a watch, the 

 progress of a coach or ship, or the evolutions 

 of a person in a dance. 



We are, therefore, to consider this natural 

 day, or twenty-four hours, as the original 

 and invariable standard of time. It is the 

 only standard which we know to be quite 

 invariable, and even it is not of uniform 

 length at all seasons of the year, as told by 

 the sun or any other of the celestial bodies. 

 There are four times in the year when the 

 hour by the sun and by a perfectly true 

 clock momentarily correspond ; and these 

 are the two equinoxes in spring and autumn, 

 and the two solstices in summer and winter. 

 At all other times of the year, the clock and 

 the sun vary in consequence of the earth's 

 motion in declination, so that in the first and 

 third quarters the clock is behind the sun- 

 dial, and in the second and fourth it is before. 

 The difference of these is a matter of easy 

 calculation to any one acquainted with as- 

 tronomy. It is called the equation of time. 



From the motion of the earth round the 

 sun in the course of the year, the sun appears 

 to have a motion eastward among the stars, 

 so as to get completely round the heavens, 

 as from star to star, in the course of the *y ear. 

 This makes the year, counted by the stars, 

 contain a day more than the year counted 

 by the sun ; the first being called the sidereal 

 year, and the second the tropical. It is by 

 the tropical year that we count time ; and at 

 present the tropical year contains three hun- 

 dred and sixty-rive days, five hours, forty- 

 eight minutes, and forty -nine seconds. This 

 odd time is less than a quarter of a day, by 

 eleven minutes and eleven seconds ; and thus 

 it will not count exactly in days or any part 

 of a day. It is, however, very nearly a 

 quarter of a day; and, thus, in our estimate 

 of the year, so as to get it expressed in an 

 exact number of days, we take no notice of 

 this fraction for three years, but reckon the 

 year for these as consisting exactly of three 

 hundred and sixty-five days ; and in order to 

 make the seasons in our calculation keep to 

 the season in the estimate, we allow the 

 fraction to accumulate, and reckon every 

 fourth year a day more, or three hundred 

 and sixty-six days, by which means we get 



an odd day, or a twenty-ninth day of Feb- 

 ruary every fourth year ; nor are we at any 

 loss to find out the year in which this is the 

 case, for whenever the date, or number of 

 the year, can be divided by four without any 

 remainder, it will be leap year ; thus, 1848 

 was a leap year, 1852 is a leap year, 1856 

 will be a leap year, and so on. 



This allowance is too much, however, and 

 the difference amounts to rather less than a 

 day in a hundred years, or very nearly to 

 seven days in nine hundred years. The 

 calendar, reckoning three hundred and sixty- 

 five days every year, and three hundred and 

 sixty-six every fourth year, was established 

 by Julius Csesar ; but as it made the year 

 by account the odd minutes and seconds 

 longer than the true year, the seasons got 

 in advance of their estimated times accord- 

 ing to the calendar. This was rectified in 

 1582 by Pope Gregory XIII., who directed 

 that the fifteenth day of October that year 

 should immediately follow the fourth day, 

 thus leaving out eleven days. It was not 

 till 1752 that the alteration was established 

 by authority in England ; and this was called 

 the alteration from "old style" to "new 

 style," the fourteenth of September coming 

 immediately after the second in that year, 

 instead of the third. Another important 

 arrangement was made at the same time. 

 Before then, it had been customary to reckon 

 the twenty-fifth day of March as the first day 

 of the year ; but at that time it was changed 

 to the first of January. In consequence of 

 this change of the beginning of the year, we 

 sometimes meet with dates which are marked 

 double, the period between January and 

 March having the number of both years at- 

 tached to it, as belonging to the old year by 

 the one estimate, and the new year by the 

 other. The Russians continue to count 

 time by the old style ; and as there has been 

 another day allowed for since our alteration, 

 the difference between Russia and the rest 

 of Europe is now twelve days ; so that an 

 English letter might arrive in Russia before 

 the day on which it appeared to be written ; 

 and a letter brought from Russia to this 

 country would be twelve days older than 

 the time of bringing. 



The day in four years, or the quarter of a 

 day every year, is more than eleven minutes 

 too much ; and, if we were not to make al- 

 lowance for this, the error which was cor- 

 rected by J?ope Gregory would accumulate 

 and have to be corrected again. We con- 

 trive, however, to get nearly rid of it by 

 leaving out the odd clay in those centuries 

 the dates of which are divisible by four 

 hundred, and which would contain three 

 hundred and sixty-six days by the common 

 estimate. This is so near the truth, that it 

 does not amount to an entire day in three 



