patiently and silently at this very profound and difficult problem for 1¾ years when he found himself able to forward to Airy, who had become Astronomer Royal after being a Cambridge Professor, some provisional elements of an imaginary planet of a size, at a distance, and in a position to meet the circumstances. It is greatly to be regretted, on more grounds than one, that Airy did nothing but pigeon-hole Adams’s papers. Had he done what might have been, and probably was, expected, that is, had he made them public, or better still had he made telescopic use of them, a long and unpleasant international controversy would have been avoided, and Adams would not have been robbed in part of the well-deserved fruits of his protracted labours. We must now turn to consider something that was happening in France. In the summer of 1845, just before Adams had finished his work, and one and a half years after he commenced it a young Frenchman, who afterwards rose to great eminence, U. J. J. Le Verrier, turned his attention to the movements of Uranus with a view of ascertaining the cause of their recognised irregularity. In November 1845 he made public the conclusion that those irregularities did not exclusively depend upon Jupiter or Saturn. He followed this up in June 1846 by a second memoir to prove that an unknown exterior planet was the cause of all the trouble, and he assigned evidence as to its position very much as Adams had done 8 months previously. Airy on receiving a copy of Le Verrier’s memoir seems so far, at last, to have been roused that he took the trouble to compare Le Verrier’s conclusions with those of Adams so long in his possession neglected. Finding that a remarkably close accord existed between the conclusions of the two men, he came to realise that both must be of value, and he wrote a fortnight later to suggest to Professor Challis the desirability of his instituting a search for the suspected planet. Challis began within two days, but was handicapped by not having in his possession any map of the stars in the neighbourhood suggested as the _locale_ of the planet. He lost no time however in making such a map, but, of course, the doing so caused an appreciable delay, and it was not until September 29, 1846, that he found an object which excited his suspicions and eventually proved to be the planet sought for. It was subsequently ascertained that the planet had been recorded as a star on August 4 and 12, and that the star of August 12 was missing from the zone observed on July 30. The discovery of the planet was therefore just missed on August 12 because the results of each evening’s work were not adequately compared with what had gone before.