THE EXCENTRICITY OF THE EARTH'S ORBIT. 



409 



table, which is given by Sir C. Lyell in the last edition of 

 the " Principles of Geology."* 



Table showing the variations in the excentricity of the earth's 

 orbit for a million years before A.D. 1800, and some of the 

 climatal effects of such variations. 



EXPLANATION OF THE TABLE. 



COLUMN 1. Division of a million years preceding 1800 into twenty equal parts. 



COLUMN 2. Computed by Mr. James Croll, by aid of Leverrier's formula, gives 

 the excentricity of the earth's orbit, in parts of a unit equal to the mean distance, 

 or half the longer diameter of the ellipse. 



COLUMN 3. Which, together with the three following columns, has been com- 

 puted by Mr. John Carrick Moore, gives in millions of miles the difference between 

 the greatest and least distances of the earth from the sun, during the excentricities 

 given in Column 2. 



COLUMN 4. Gives the number of days by which winter, occurring in aphelion, 

 is longer than the summer in perihelion. 



COLUMN 5. Gives the mean temperature of the hottest summer month in the 

 latitude of London when the summer occurs in perihelion. 



COLUMN 6. Gives the mean temperature of the coldest winter month in the 

 latitude of London when the winter occurs in aphelion. 



* 1. c. vol. i. p. 293. 



