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Proceedings of the Royal Society 
during the final years of his official career and life itself, — all good 
men were aware that his indefatigable, most original, and innate, 
unapproachable genius was again toilsomely engaged on the grand, 
self-imposed task of his life ; and was even then rapidly and mag- 
nificently preparing as full mathematical theories and accurate 
practically-computing numerical tables of the larger, outer planets 
of the Solar System, as he had already done for the smaller, 
inner members thereof. His analytical methods too were the 
most comprehensive that had ever been attempted ; and were 
specially distinguished by their capacity to take in and utilise all 
good observations ever made in practical astronomy on the bodies 
concerned, through all time, whether ancient or modern. The 
work was immense, and it killed him in the end, though not before 
he had satisfactorily finished it, even to the last page. 
He had even the peculiar satisfaction before his death of seeing 
his most difficult researches, almost in mathematical darkness, as to 
the mass of the planet Mars— up to that time supposed by all the 
world to be “ moonless Mars” — suddenly lighted up and confirmed 
by the splendid and most unexpected American discovery of this 
last summer, with their latest erected and largest equatorial telescope 
at Washington, of two moons circulating around that planet, and 
at rates of motion which admirably bore out his, Le Yerrier’s, 
intellectually concluded number for its mass and consequent power 
of gravitational attraction. But so truly immense, as well as 
idtra difficult, was the whole planetary research, that not only 
(as has been well said elsewhere) would it have been considered 
mpossible for one man to have achieved the whole, if Le Yerrier 
had not performed it in our own times, — but, only one man has 
been found fully able even to describe the w’ork to others ; and that 
one man is, — who 1 
Le Yerrier’s early, unconscious, but unexceptionable, and equally 
successful rival, in his greatest astronomical calculation, prediction, 
and discovery, with regard to the once unknown planet, which 
we all now so glibly call Neptune, — viz., the then young J. C. 
Adams, of St John’s College, Cambridge. 
Professor Adams has indeed not only described, in a late Presi- 
dential address to the Koyal Astronomical Society of London, Le 
Yerrier’s life long problems of the planetary orbits, — with an 
