18 



The following table shows the average temperature ami arcrage fall of rain in 

 the different States during the month of July for the years named. Av> reports 

 for this year loerc received from two of the States. 



TEMPERATURE OF JULY. 



As a whole, the earth receives less heat from the sun in July than in any 

 other month of the year. Our planet does not revolve around the sun in a cir- 

 cular, but in an elliptical or elongated orbit, and therefore is nearer the central 

 luminary at one season of the year than another. At the present time — that is, 

 near the middle of the 19th century — the earth is nearest the sun on the 1st of 

 January, and furthest from it on the fourth of July ; or, in other words, the 

 whole earth receives the greatest amount of heat from the sun on New Year's 

 day, and the least on the anniversary of our national independence. 



This condition of affairs is not permanent, but is constantly, though very 

 slowly, changing. In about ten thousand years the earth will be nearest the 

 sun in July, and furthest from it in January. This will very much hicrease 

 the intensity of the heat of the northern summer and the cold of the northern 

 winter. The cause above mentioned is, however, too slow in its operations to 

 have produced any very appreciable effect during our historic period, although 

 in the long geological ages it probably assisted in producing the changes of 

 climate, which are proved from the remains of plants and animals to have taken 

 place on different parts of the earth's surface. 



What we have said relates to the heat received from the sun by the Avhole 

 earth, and not to the heat of any place in different seasons of the year. Tin- 



