great circle of a sphere, and since this circle is 

 equally divided into four parts, by the four points, 

 which I have just mentioned as determining the 

 seasons, that the four seasons should have been 

 equal in duration. Centuries, however, before 

 the Christian era, it had been discovered that 

 this was not the case, a circumstance which it 

 would be difficult to have presupposed, seeing 

 that the circumference of a circle is, by the very 

 nature of the curve, similarly situated in every 

 part, with respect to the centre. The fact is, 

 that the summer months are about eight days 

 longer than the winter ones, and an investigation 

 of these apparent phenomena ultimately led to 

 the figure of the earth's orbit, which is now well 

 known to be an ellipse a curve, which possesses 

 a variety of curious properties, and which being 

 formed by a certain intersection of a cone, has 

 been called a conic section. Thus it is that the 

 eliptic circle, being the perspective representa- 

 tion of the ellipse on the concave surface of the 

 heavens, must of course exhibit all the irregula- 

 rities of the original, and we thus see the reason 

 of the seasons being unequal in duration. In 

 considering the effects of the apparent motion of 

 the sun, it is usual to designate the nearest ap- 

 proach of the earth as perigee, and its farthest 

 distance as apogee ; and from what I have just 

 said, it is evident that the summer and winter 

 months can never be equally divided, but in the 

 particular case of the coincidence of the solar 

 perigee, with one or other of the equinoxes. 



