df the Terrestrial Globe. . 221 



The sun is not always equally distant from the earth. At 

 this time its least distance is observed in the first days of Janu- 

 ary, and the greatest, six months after, or in the first days of July. 

 But, on the other hand, a time will come when the minimum 

 will occur in July, and the maximum in January. Here then, 

 this interesting question presents itself, — Should a summer, 

 such as those we now have, in which the maximum corresponds 

 to the solar distance, differ sensibly, from a summer with which 

 the minimum of this distance should coincide ? 



At first sight every one probably would answer in the affirma- 

 tive ; for, between the maximum and the minimum of the sun's 

 distance from the earth, there is a remarkable difference, a 

 difference in round numbers of a thirtieth of the whole. LtQXy 

 however, the consideration of the velocities be introduced into 

 the problem, elements which cannot fairly be neglected, and 

 the result will be on the side opposite to that we originally 

 imagined. 



The part of the orbit where the sun is found nearest the 

 earth, is, at the same time, the point where the luminary moves 

 most rapidly along. The demi-orbit, or in other words, the 

 180° comprehended betwixt the two equinoxes of spring-time 

 and autumn, will then be traversed in the least possible time, 

 when, in moving from the one of the extremities of this arc to 

 the other, the sun shall pass, near the middle of this course of 

 six months, at the point of the smallest distance. To resume — 

 the hypothesis we have just adopted, would give, on account of 

 the lesser distance, a spring-time and summer hotter than they 

 are in our days; but on account of the greater rapidity, the 

 sum of the two seasons would be shorter by about seven days. 

 Thus then, all things considered, the compensation is mathema- 

 tically exact. After this it is superfluous to add, that the point 

 of the sun*s orbit corresponding to the earth's least distance, 

 changes very gradually ; and that since the most distant pe- 

 riods, the luminary has always passed by this point, cither at 

 the end of autumn or beginning of winter. 



We have thus seen that the changes which take place in the 

 position of the solar orbit, have no power in modifying the 

 climates of our globe. We may now inquire, if it be the same 

 concerning the variations which this orbit experiences in xisjbrm. 



VOL. XVI. NO. XXXII. APRIL 1834. ^ 



