58 Mr. Robertson on the Precession 
conclusion, in consequence of a mistake committed in some 
part of the proceedings. The second head may be allotted to 
those in which the conclusions may be admitted as just, but 
rendered so by the counteraction of opposite errors. Such 
may be ranked under the third head as are conducted without 
error fatal to the conclusion, and in which the result is as 
near the truth as the subject seems to admit. 
The authors of those investigations, of each of the three 
descriptions, are entitled to much praise. Their productions 
afford the most unquestionable proofs of great talents, great 
zeal, and great perseverance, exerted in the cultivation of 
science. The mistakes committed in those of the two first 
descriptions, and the obscurity and perplexity with which 
those of the third may be charged, are, in my opinion, to be 
attributed to the same cause, the uncultivated state of that 
particular department of the doctrine of motion, which con- 
stitutes the appropriate foundation for the solution of the 
problem. The department to which I allude is that of com- 
pound rotatory motion. 
In consequence of this persuasion I have, in the first nine 
of the following articles, endeavoured to investigate the pri- 
mary properties of compound rotatory motion from clear and 
unexceptionable principles. The disturbing solar force on 
the spheroidal figure of the earth is then calculated, and the 
angular velocity which it produces is afterwards compared 
with that of the diurnal revolution, by means of the properties 
of rotatory motion previously demonstrated. The quantity 
of annual precession is then calculated in the usual way, and 
also that of nutation, as far as they are produced by the 
disturbing force of the sun. 
