142 On the Precession of the Equinoxes. 
the ecliptic angle caused principally by the moon’s attraction, 
Now Lask if the diminution of the angle to produce the nu a- 
tation of the poles will not necessarily prod p ionof 
the equinoxe ? Further, he says, it cannot arise from a dim- 
inution of the ecliptic angle, for that would produce a sen- 
sible effect upon the seasons, It would diminish the angle 
ut a few seconds, and consequently would have about as 
much effect upon the seasons, at any given place, as a person 
would experience by moving N. or S. 5 miles. Dr. Brad- 
ley, Vince and some others have calculated what the dim- 
inution of the angle should be, and find that the calcula- 
tions agree with fact. 
What is meant by saying, that the precession of the equi- 
noxes “must arise’—* from a change in the direction of 
the line of the nodes,” I am nat able to tell. 
Since calculations have been made relative to the power 
of the attraction of the sun and moon upon the equatorial 
ring, and since the calculated effects of the same corres- 
pond so precisely with facts, I must say that I am not able 
to see the validity of the writers objections to the old 
theory. . 
I think there are some insuperable objections to the new 
theory, two of which 1 will mention. 
1. The diameter of the ‘“‘ orbis mundorum,” must be of 
very great length. The system must perform a revolution 
in 25920 years. If the orbit be circular the system must 
move uniformly, and consequently the annual precession of 
the equinoxes must be uniform. But if the “ orbis mun- 
dorum” be an ellipse, then the system either moves with ap 
accelerated or retarded velocity. Now the precession of the 
equinoxes is in fact quite irregular. How then I ask cap 
this irregular precession be produced by the regular mo- 
tion of the system about a distant centre. : 
2. The attraction of the “ distant centre” must be im- 
mensely great, and probably would affect the motion of the 
earth in the ecliptic nearly as much as the sun affects the 
motion of the moon revolving about the earth. While the 
earth is passing from that part of the ecliptic the most re- 
mote from the * distant centre” to the part nearest, its MO 
tion would be accelerated, and in passing through the oth- 
er half of the ecliptic retarded. ‘To find accurately then 
the apparent place of the sun in the ecliptic for any give" 
? 
