184 
ADDRESS DELIVERED BY THE PRESIDENT. 
[579 
the observations with the provisional theory. Fourthly, the correction of the elements 
of the provisional theory, viz. the equations for the comparison of the longitudes give 
8e, hi, hi, 8k, and a correction to the assumed mass of Neptune, which mass is thus 
brought out = Y$b?o‘ And the equations for the comparison of latitudes give 8p, 8q; 
there is thus obtained a corrected set of elements (Newcomb’s Elements IV.), being 
for the year 1850, the elements as affected with the long inequality; these are the 
elements upon which the Tables are founded. But it is theoretically interesting to 
have the absolute mean values of the elements, and the author accordingly obtains 
these (his Elements V.) together with the corrections corresponding to a varied mass 
of Neptune, (^that is, the terms in p corresponding to a mass q 97(>0J ’ remar k s 
that, admitting the mass of Neptune to be uncertain by about one-hftieth of its value, 
he remarks 
the mean longitude of the perihelion of TJranus is from this cause uncertain by more 
than two minutes, the mean longitude of the planet by nearly a minute, and the 
mean motion by nearly two seconds in a century. Fifthly, the formation of the tables, 
based on the Elements IV.; the tables calculated with these elements are intended 
to hold good for the period between the years 1000 and 2200; but by aid of the 
Elements V. they may be made applicable for a more extended period. 
In what precedes I have endeavoured to give you an account of Professor Newcomb’s 
writings: they exhibit all of them a combination, on the one hand, of mathematical 
skill and power, and on the other hand of good hard work—devoted to the furtherance 
of Astronomical Science. The Memoir on the Lunar Theory contains the successful 
development of a highly original idea, and cannot but be regarded as a great step in 
advance in the method of the variation of the elements and in theoretical dynamics 
generally; the two sets of planetary tables are works of immense labour, embodying 
results only attainable by the exercise of such labour under the guidance of profound 
mathematical skill—and which are needs in the present state of Astronomy. I trust 
that imperfectly as my task is accomplished, I shall have satisfied you that we have 
done well in the award of our medal. 
The President then, delivering the medal to the Foreign Secretary, addressed him in 
the following terms: 
Mr Huggins—I request that you will have the goodness to trausmit to Professor 
Newcomb this medal, as an expression of the opinion of the Society of the excellence 
and importance of what he has accomplished; and to assure him at the same time 
of our best wishes for his health and happiness, and for the long and successful 
continuation of his career as a worker in our science.