384 FERGUSON'S LECTURES. 



LECT. will be 15 degrees contained between any two of these 



VTlT fi T"Y 



\^/~ meridians which are nearest to one another ; for 24 times 

 15 is 360. And as the earth's motion is eastward, the 

 sun's apparent motion will be westward, at the rate of 

 15 degrees each hour. Therefore, 



Longitude. They whose geographical meridian is fifteen degrees 

 eastward from us, have noon, and every other hour, an 

 hour sooner than we have. They whose meridian is 

 fifteen degrees westward from us, have noon, and every 

 other hour, an hour later than we have ; and so on in 

 proportion, reckoning one hour for every fifteen 

 degrees. 



As the earth turns round its axis once in 24 hours, 

 and shews itself all round to the sun in that time ; so 

 it goes round the sun once a year, in a great circle call- 

 Eeliptic. ed the ecliptic, which crosses the equinoctial in two op- 

 posite points, making an angle of 32j degrees with the 

 equinoctial on each side. So that one half of the eclip- 

 tic is in the northern hemisphere, and the other in the 

 southern. It contains 360 equal parts, called degrees, 

 (as all other circles do, whether 'great or small) and as 

 the earth goes once round in every year, the sun will 

 appear to do the same, changing his place almost a de- 

 gree, at a mean rate, every 24 hours. So that whatever 

 place or degree of the ecliptic, the earth is in at any 

 time, the sun will then appear in the opposite. 



And as one half of the ecliptic is on the north side of 

 the equinoctial, and the other half on the south ; the sun 

 as seen from the earth, will be half a year on the south 

 side of the equinoctial, and half a year on the north ; 

 and twice a year in the equinoctial itself. 

 Signs and The ecliptic is divided by astronomers into 12 equal 



cgreea. p &rtg ^ ca ]] e( j s ig nS} each sign into 30 degrees, and each 

 degree into 60 minutes; but in using the globes, we sel- 

 dom want the sun's place nearer than half a degree of 

 the truth. 



