motion on it's axis, any given meridian will revolve from any ftar to the fame ftar again, in every abfolute turn of the earth upon it's axis, without the least perceptible difference of time being shewn by a clock which goes exactly true.

If the earth had only a diúrnal, without an annual motion, any given meridian would revolve from the fun to the fun again, in the fame quantity of time as from any ftar to the fame star again; because the fun would never change his place, with respect to the stars. But as the earth advances almost a degree eastward in it's orbit, in the time that it turns eastward round it's axis, whatever ftar paffes over the meridian on any day with the fun, will pafs over the fame meridian on the next day, when the fun is almost a degree fhort of it, that is, 3 min. 56 feconds fooner. If the year contained only 360 days, the fun's apparent place, fo far as his motion is equable, would change a degree every day, and then the fiderial days would be just four minutes shorter than the folar..

Let ABCDEFGH, fig. 3, plate IV. be the earth's orbit, in which it goes round the fun every year, according to the order of the letters, that is, from west to eaft, and turns round it's

axis the fame way, from the fun to the fun again in every twenty-four hours. Let S be the fun,

and R a fixed star, at such an immenfe diftance, that the diameter of the earth's orbit bears no fenfible proportion to that distance; N m n the earth in different points of it's orbit. Let Nm be any particular meridian of the earth, and Na given point, or place, lying under that meridian.

When the earth is at A, the fun S hides the star R, which would always be hid if the earth never moved from A, and confequently as the earth turns round it's axis, the point N would always come round to the fun and the ftar at the fame time.

But when the earth has advanced through an eighth part of it's orbit, or from A to B, it's motion round it's axis will bring the point N an eighth part of a day, or three hours, fooner to the ftar than to the fun. For the ftar will come to the meridian in the fame time as though the earth had continued in it's former fituation at A, but the point N must revolve from N to n, before it can have the fun upon it's meridian. The arc Nn being therefore the fame part of a whole circle, as the arc A B, it is plain that any ftar which comes to the meridian at noon, with the fun,

when

when the earth is at A, will come to it at nine o'clock in the forenoon, when the earth is at B.

When the earth has paffed from A to C, onefourth part of it's orbit, the point N will have the ftar upon it's meridian, or at fix in the morning, fix hours fooner than it comes round to the fun; but the point N must revolve fix hours more, before it has mid-day by the fun : for now the angle ASD is a right angle, and fo is N Dn; that is, the earth has advanced 90 degrees on it's axis, to carry the point N from the star to the fun; for the ftar always comes to the meridian when Nm is parallel to RSA; because DS is but a point in respect to R S. When the earth is at D, the ftar comes to the meridian at three in the morning, at E, the earth having gone half round it's orbit; N points to the ftar at midnight, it being then directly opposite to the fun; and, therefore, by the earth's diurnal motion, the star comes to the meridian twelve hours before the fun, and then goes on, till at A it comes to the meridian with the fun again.

Thus it is plain, that one abfolute revolution of the earth on it's axis, (which is always completed when any particular ftar comes to be

parallel

parallel to it's fituation at any time of the day before) never brings the fame meridian round from the fun, to the fun again; but that the earth requires as much more than one turn on it's axis, to finish a natural day, as it has gone forward in that time, which, at a mean state, is a 365th part of a circle.

From hence we obtain a method of knowing by the stars, whether a clock goes true or not. For if through a small hole in a window-fhutter, or in a thin plate of metal fixed to a window, we observe at what time any star disappears behind a chimney, or corner of a house, at a little distance; and if the fame ftar disappears the next night, 3 min. 56 feconds, fooner by the clock; and on the fecond, 7 minutes, 52 feconds fooner; the third night, 11 minutes, 48 feconds fooner, and fo on every night; it is an infallible fign that the machine goes true; otherwise it does not, and must be regulated accordingly. This method may be depended on to nearly half a fecond.

OF THE SEASONS OF THE YEAR.

It is our business under the prefent head to account for the phænomena of the seasons, those grateful viciffitudes on which fo much, both of

the business and happiness of man depends. As the seasons are applied in the hieroglyphic language of the bible, to mark the different ftages. of man's progress in virtue, the rife, meridian glory, decline, and confummation of the church,. or the different difpenfations of divine goodness and truth to man; we do not think the reader will be offended, if we present him with a few obfervations on this head, extracted from the works of an elegant moralist.

The natural advantages which arife from the pofition of the earth which we inhabit, with respect to the other planets, afford much employment to mathematical fpeculation; by which it has been discovered, that no other conformation. of the system could have given fuch commodious diftributions of light and heat, or imparted fertility and pleasure to fo great a part of a revolving sphere.

The moralift may with equal reafon observe, that our globe seems equally fitted for the refidence of a being, placed here only for a fhort time, whofe task is to advance himself to a higher and happier ftate of existence, by unremitted vigilance of caution, and activity of virtue. The duties of man are fuch as human nature does not

willingly