INTRODUCTION. XXlll. 



The Precession of the Equinox may be 

 thus explained : — The equinoctial points are always 

 westering, that is, getting back among the pre- 

 ceding signs of stars, at the rate of about fifty 

 seconds each year, which retrogade motion is called 

 the precession, or sometimes the retrocession, of 

 the equinoxes. As then the fixed stars remain 

 immoveable, and the equinoxes go backward, the 

 stars Avill seem to move more and more eastward 

 with respect to them ; whence the longitudes of 

 the stars, which are reckoned from the first point 

 of x\ries, are continually increasing. On this ac- 

 count, the interval of time between the equinox, 

 and that same equinox, in the following revolution 

 of the earth, which is called tropical year, is some 

 minutes shorter than the sidereal year, or the period 

 in which the earth revolves from one point of her 

 orbit to the same point again. 



The Weather. — This is perhaps the most 

 interesting time of the whole year ; and though at 

 the beginning the rough equinoctial gales are apt 

 to return, yet the intervals of bright weather which 

 come between the showers afford perhaps speci- 

 mens of the clearest skies which occur in our 

 climate. We liave known thunder showers with 

 very highly electrified hail happen in this season, 

 and in some instances snow ; but it has been of 

 short continuance. The latter part, however, in- 

 cluding the flowery days of early May, is the 



