104 THE MOON. 



the centre of an ellipse but in the focus, the earth must 

 move farther in its orbit in one pari of its revolution than in 

 the other. It moves slovver also as it is farther from the 

 sun ; and our summers are found to be eight days longer 

 than the summers in south latitude ; that is, between the 

 vernal and autumnal equinoxes there are eight days more, 

 than between the autumnal and vernal. 



It is well known that the degree of heat is not greatest, 

 when the days are longest. We have the warmest weather 

 in the latter part of July, and in the first of August ; and 

 our coldest month is January. To account for this it has 

 been stated, that a body once heated does not grow cold 

 again instantaneously, but gradually ; now as long as more 

 heat comes from the sun in the day, than is lost in the night, 

 the heat of the earth and air will be daily increasing, and 

 this must evidently be the case for some weeks after the 

 longest day, both on account of the number of rays which 

 fall on a given space, and also from the perpendicular di- 

 rection of those rays. It is for the same reason, that the 

 warmest part of the day is not, when the sun is at the me- 

 ridian, but ai)out two or three o'clock in the afternoon. 



Questions. — I. When are those who live in north latitude nearest 

 the sun ? 2. What would be the conscquenfo ifflic equator coincided 

 with the eclipric ? 3. What occasions the seasons witli us ? 4.^ How 

 may the effect of obliquity in regard to the sun's rays be made evident ? 

 5. Wliat contributes much to the warmth of summer? 6. What is 

 said of north and south latitudes as respects the degree of heat ? — Ex- 



fdain. 7. Why is not the degree of heat greatest when the days are 

 ongest ? 8. Look at fig. 40, and illustrate the diversity of the seasonB. 



LESSON 47. 

 The 3Ioon. 



Quad'rature, the first and last quarter of the moon. 

 Lu'nar, relating to the moon. Luna'tion, the revolution of the 

 moon. 



The moon is a secondary planet, revolving round the 

 earth in about twenty-nine days and a half, and is carried 

 with the earth round the sun once a year. Its distance 

 from the earth is about two hundred and forty thousand 

 miles ; and it turns on its axis in the same time that it per- 



