Hill

weeks later. Hill was a man of few gifts and of
limited mentality, but in Yankee comedy he has
never had his equal.

ILife and Recollections of Yankee Hill (1850), ed.
by W. K. Northall, contains a biography by the editor.
Scenes from the Life of an Actor (1853) is a partially
autobiographical account. See also J. N. Ireland, Rec-
ords of the N. Y. Stage (2 vols., 1866-67); G. C. D.
Odell, Annals of the N. Y. Stage, vols. Ill and IV
(1928) ; Evening Post (N. Y.), Oct. 2, 1849.]

O.S.C.

HILL, GEORGE WILLIAM (Mar. 3, 1838-
Apr, 16,1914), mathematician, was born in New
York City, the son of John William Hill, an
artist and engraver, and Catherine (Smith) Hill
of English and Huguenot descent. His paternal
grandfather was John Hill [q.v.]. In 1846 the
family moved to a farm in West Nyack where he
attended the local school. Later he went to Rut-
gers College and had the good fortune to come
under an able teacher, Dr. Theodore Strong
[g.p.], who gave him a thorough grounding in
the fundamentals of mathematics and celestial
mechanics by making him study the classical
treatises of Euler, Lacroix, Laplace, Lagrange,
and Legendre. He took his degree in 1859 an^
during the following thirteen years he must have
spent a good deal of time mastering the later
works on the lunar and planetary theories, es-
pecially those of Delaunay and Hansen. His
own publications on those subjects began in
1872. It was this training that probably gave
the trend to all his work—the application of
mathematical analysis to the investigation of
natural phenomena, with the final step of re-
ducing the results to numerical data. In 1861 he
joined the staff of the Nautical Almanac Office
and spent a year or two in Cambridge, Mass.,
which was its headquarters at that time. Soon,
however, he obtained permission to do his work
at his home in West Nyack, and from then to
the time of his death his only absences for any
considerable period were the ten years, 1882-92,
which he spent in Washington working on the
theory and tables of Jupiter and Saturn, a trip
to Europe, and two holidays in the northwest of
Canada. He never married. His later life he
spent alone on his farm, taking his meals with
a married brother who lived nearby. He was
essentially of the type of scholar and investigator
who seems to feel no need of personal contacts
with others. While the few who knew him speak
of the plea$ure of his companionship in frequent
tramps over the country surrounding Wash-
ington, he was apparently quite happy alone,
whether at work or taking recreation. This iso-
lation seems to have had no effect on him other
than to preserve the independence of his ideas
and to emphasize a natural indifference to ex-

Hill
ternals: his intellectual outlook was always es-
sentially sane. His one mild extravagance, the
buying of books, was probably due to his desire
to remain at home. He read somewhat widely,
especially in botany, his hobby.
His ability was first decisively shown in a
memoir entitled "Researches in the Lunar Theo-
ry," which appeared (1878) in the opening num-
ber of the newly founded American Journal of
Mathematics. In this paper he calculated the
first step in a new method for treating the mo-
tion of the moon under the attractions of the
earth and sun. What proved to be equally im-
portant in the paper was the initiation of the
"periodic orbit"—an idea which has had a pro-
found effect on the later development of celestial
mechanics. In the hands of H. Poincare, G. H.
Darwin, and many others, it has greatly changed
the approach to the study of the motions of three
mutually attracting bodies. Its publication gave
new life to a subject which had seemed to be
marking time in merely securing higher nu-
merical accuracy for the various gravitational
theories of the bodies in the solar system, and
the impetus is not yet exhausted. Another useful
idea, the surface of zero velocity, is also set forth
in this paper. The second step, which was ac-
tually published the previous year in a paper, On
the Part of the Motion of the Lunar Perigee
Which is a Function of the Mean Motions of the
Sun and Moon (1877), displays Hill's analytical
skill in a marked degree. His initiation of the
infinite determinant and the devices which he
used to calculate its value to a high degree of
accuracy were nearly all new. In this paper,
also, he showed his unusual capacity to carry
out accurately a long and intricate calculation.
Shortly after the publication of these papers Hill
was persuaded by Simon Newcomb to under-
take a new theory of the motions of Jupiter and
Saturn. This theory and the formation of the
necessary tables occupied him until 1892. In
order to avoid delay in completing the work,
which was mainly a laborious and involved set
of computations, Hill used a well-known meth-
od, that of Hansen. This was perhaps unfor-
tunate, for Hill was then at the height of his
powers and if given more time he might have
produced a new method which would have been
of service in other similar problems. He was
unwilling to use routine computers, finding it
more trouble to explain what was to be done
than to do it himself. The final result is one of
the most important contributions to mathemati-
cal astronomy of the past century. Among his
later papers is a noteworthy contribution for
calculating the effects of the planets on the mo-