A WEEKLY ILLUSTRATED JOURNAL OF SCIENCE. 
“To the solid ground 
Of Nature trusts the mind which buzlds for aye.” —WORDSWORTH. 
THURSDAY, MAY 4, 1899. 
S CLE MEDLEL GC WOR TRIPLES. 
XXXII.—SIMON NEWCOMB. 
EWCOMB must be considered, without contradic- 
tion, as one of the most celebrated astronomers 
of our time, both on account of the immensity of his 
work and the unity of view which marks the choice of | 
the subjects treated by him. 
All is linked together in our solar system: the study 
of the motion of each one of the celestial bodies forming 
part of it is based upon the knowledge of a great | 
number of numerical data, and there exists no funda- | 
mental element whose influence is not repercussed on 
the entire theory of these bodies. To endeavour to 
build up the theory of our whole planetary world on an 
absolutely homogeneous basis of constants was an almost | 
superhuman task. 
The evaluation of each one of these data demands, 
indeed, that one should attentively go over most of the | 
previous researches, and continue them by more thorough 
methods. All Newcomb’s work, followed up with rare 
perseverance, has constantly tended to this ideal end: | 
the ingenious method suggested by Léon Foucault. 
first to arrive at a more exact knowledge of the magni- 
tudes serving as points of reference, and then to establish 
the theory, not only of all the planets, but also of their 
satellites on a system of constants as precise as modern 
observations permit. Wishing to realise in a complete 
manner this vast programme, Newcomb has recognised 
that the published observations do not always furnish 
the necessary information for obtaining with exactness 
all the looked-for elements. Abandoning, therefore, the 
domain of pure speculation, he has given himself up to 
researches which proclaim him possessed of a talent of 
observation of the highest order. By personal studies 
he has succeeded in filling many of the gaps which 
seriously impeded the progress of theory. Thus, in 
order to determine the masses of Neptune and Uranus 
and the elements of their satellites, he madea series of ob- 
servations of great value, on which are partially founded 
the ephemerides inserted in all nautical almanacs. 
NO. 1540, VOL. 60] 
I shall simply mention here in a few words some of 
the preparatory work preceding the construction of the 
magnificent edifice of which I have indicated the plan, 
on the happy completion of which the scientific world 
is to be congratulated. Throughout its execution one 
recognises the sign of a master-mind whose conclusions 
assume a definite character and remain acquired to 
science. 
The solar parallax is one of the most essential data 
which intervene in all researches concerning the planetary 
system. Newcomb undertook to fix its value by the dis- 
cussion of all the transits of Venus observed previously 
to 1882. In a very detailed memoir, he calls astro- 
nomers’ attention to the danger to which they are 
exposed by giving an exaggerated confidence to certain 
modern methods. The systematic exclusion of the 
ancient observations cannot sufficiently be justified by 
discordances which exist between their results and those 
obtained more recently. By a minute and impartial 
discussion of all existing documents, Newcomb arrived 
at a value almost identical with the one adopted in 1896 
by the International Conference of Paris. 
Again, in order to obtain by an altogether independent 
means the value of this same constant, Newcomb under- 
took a determination of the velocity of light, based on 
These researches of a physical nature opened the way 
to an important advance in our knowledge of the 
heavens. In fact, we had all reason to hope that the 
value obtained for the velocity of light, combined with the 
constant of aberration, would allow us to determine the 
solar parallax more accurately than by the usual astro- 
nomical methods. Newcomb holds that multiplicity of 
methods is an essential condition of success ; this motive 
led him to choose Foucault’s methcd, which he applied 
with rare sagacity. The agreement between the different 
results obtained in this way by Cornu, Michelson and 
Newcomb is an admirable one, and testifies to the 
knowledge and skill of the experimenters. With the help 
of the values found for the velocity of light, it would have 
been possible to deduce the parallax, if recent observa- 
tions had not revealed the uncertainty which still hovers 
over the real value of the aberration constants. 
B 
