568 
NOTES AND REFERENCES. 
221. It is well known that Plana, developing the explanation given by Laplace 
for the secular variation of the moon’s mean motion, obtained in the expression of 
the true longitude the terms — (f m? — j* (e' 2 — E' 2 ) ndt, and that Prof. Adams in , 
his memoir “On the Secular Variation of the Moon’s Mean Motion,” Phil. Trans, t. 143 
(1853), pp. 397—406, corrected this into — (f m 2 — ^^ 1 m 4 )J (e' 2 — E' 2 ) ndt. The validity 
of the correction was a good deal discussed, and it was interesting to establish the 
result by an entirely independent method. 
END OF YOL. III. 
CAMBRIDGE : 
PRINTED BY C. J. CLAY, M.A. AND SONS. 
AT THE UNIVERSITY PRESS.