ulable
scientific value. For millions of stars can be determined by its means,
from their imprinted images, with an accuracy comparable to that
attainable by direct meridian observations.

One of the most ardent promoters of the scheme it may be expected to
realise was Admiral Mouchez, the successor of Leverrier in the direction
of the Paris Observatory. But it was not granted to him to see the
fruition of his efforts. He died suddenly June 25, 1892.[1577] Although
not an astronomer by profession, he had been singularly successful in
pushing forward the cause of the science he loved, while his genial and
open nature won for him wide personal regard. He was replaced by M.
Tisserand, whose mathematical eminence fitted him to continue the
traditions of Delaunay and Leverrier. But his career, too, was unhappily
cut short by an unforeseen death on October 20, 1896; and the more
eminent among the many qualifications of his successor, M. Maurice
Loewy, are of the practical kind.

The sublime problem of the construction of the heavens has not been
neglected amid the multiplicity of tasks imposed upon the cultivators of
astronomy by its rapid development. But data of a far higher order of
precision, and indefinitely greater in amount, than those at the
disposal of Herschel or Struve must be accumulated before any definite
conclusions on the subject are possible. The first organised effort
towards realising this desideratum was made by the German Astronomical
Society in 1865, two years after its foundation at Heidelberg. The
original programme consisted in the _exact_ determination of the places
of all Argelander's stars to the ninth magnitude (exclusive of the polar
zone), from the reobservation of which, say, in the year 1950,
astronomers of two generations hence may gather a vast store of
knowledge--directly of the apparent motions, indirectly of the mutual
relations binding together the suns and systems of space. Thirteen
observatories in Europe and America joined in the work, now virtually
terminated. Its scope was, after its inception, widened to include
southern zones as far as the Tropic of Capricorn; this having been
rendered feasible by Schoenfeld's extension (1875-1885) of Argelander's
survey. Thirty thousand additional stars thus taken in were allotted in
zones to five observatories. Another important undertaking of the same
class is the reobservation of the 47,300 stars in Lalande's _Histoire
Celeste_. Begun under