ii Proceedings of Royal Society of Edinburgh. 
obtained which showed that an agreement between observation and 
theory might be brought about. Further, earlier data still wanting 
were supplied by the Astronomer-Eoyal, who, in February 1844, 
sent to Adams all the Greenwich observations of Uranus. 
In other quarters the irregular motion of Uranus had attracted 
attention. Our countryman. Dr Hussey, had proposed an extended 
search for an outer planet, combined with a partial survey of the 
heavens. The illustrious Bessel had devoted considerable time to 
an attempted explanation, at first on the hypothesis of an elective 
attraction on the part of Saturn. Failing health compelled him to 
hand the work over to one of his assistants, whose health in turn 
also gave way before anything was accomplished beyond a reduction 
of the older observations. The Royal Academy of Sciences of 
Gottingen, however, proposed the Theory of Uranus as their mathe- 
matical prize ; and although Adams tells us that his college duties 
prevented him from attempting the complete examination of the 
theory, which a competition for the prize would have required, yet 
this fact, together with the possession of such a valuable series of 
observations, induced him to undertake a new solution of the problem. 
With indomitable perseverance the subject was now attacked by the 
sure method of successive approximations. Hot one solution, but 
several solutions were obtained, differing little from each other. 
Gradually more and more terms of the perturbational series were 
taken into account, until at last, in September 1845, he was able 
to communicate to Professor Challis the definite values he had 
obtained for the mass, the heliocentric longitude, and the elements 
of the orbit of the assumed planet. Slightly corrected results were 
communicated to the Astronomer-Royal a month later. But 4-dams 
did not rest content. The excentricity being larger than was pro- 
bable, the whole investigation was again repeated, using a less mean 
distance. The final result was communicated to Mr Airy in the 
beginning of September 1846. 
Meanwhile, on Hovember 10th, 1845, the brilliant young French 
astronomer, Le Verrier, had presented to the French Academy a 
most thorough investigation of the orbit of Uranus as perturbed by 
Saturn and Jupiter, taking into account several minute perturbations 
neglected by Bouvard. This he followed up by a second memoir 
presented on the 1st of June 1846 (or nine months later than 
