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II. On the Precession of the Equinoxes. By the Rev . Abram 
Robertson, M. A. F. R. S. Savilian Professor of Geometry in 
the University of Oxford . 
Read December 18, 1806. 
Perhaps the solution of no other problem, in natural philo- 
sophy, has so often baffled the attempts of mathematicians as 
that of determining the precession of the equinoxes, by the 
theory of gravity. The phenomenon itself was observed about 
one hundred and fifty years before the Christian aera, but Sir 
Isaac Newton was the first who endeavoured to estimate its 
magnitude by the true principles of motion, combined with 
the attractive influence of the sun and moon on the spheroidal 
figure of the earth. It has always been allowed, by those 
competent to judge, that his investigations relating to the 
subject evince the same transcendent abilities as are displayed 
in the other parts of his immortal work, the mathematical 
Principles of natural Philosophy, but, for more than half 
a century past, it has been justly asserted that he made a 
mistake in his process, which rendered his conclusions erro- 
neous. 
Since the detection of this error, some of the most eminent 
mathematicians in Europe have attempted solutions of the 
problem. Their success has been various ; but their investi- 
gations may be arranged under three general heads. Under 
the first of these may be placed such as lead to a wrong 
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