n 1830 in his _Tabulae
Regiomontanae_. They not only constituted an advance in accuracy, but
afforded a vast increase of facility in application, and were at once
and everywhere adopted. Thus astronomy became a truly universal science;
uncertainties and disparities were banished, and observations made at
all times and places rendered mutually comparable.[65]

More, however, yet remained to be done. In order to verify with greater
strictness the results drawn from the Bradley and Piazzi catalogues, a
third term of comparison was wanted, and this Bessel undertook to
supply. By a course of 75,011 observations, executed during the years
1821-33, with the utmost nicety of care, the number of accurately known
stars was brought up to above 50,000, and an ample store of trustworthy
facts laid up for the use of future astronomers. In this department
Argelander, whom he attracted from finance to astronomy, and trained in
his own methods, was his assistant and successor. The great "Bonn
Durchmusterung,"[66] in which 324,198 stars visible in the northern
hemisphere are enumerated, and the corresponding "Atlas" published in
1857-63, constituting a picture of our sidereal surroundings of
heretofore unapproached completeness, may be justly said to owe their
origin to Bessel's initiative, and to form a sequel to what he
commenced.

But his activity was not solely occupied with the promotion of a
comprehensive reform in astronomy; it embraced special problems as well.
The long-baffled search for a parallax of the fixed stars was resumed
with fresh zeal as each mechanical or optical improvement held out fresh
hopes of a successful issue. Illusory results abounded. Piazza in 1805
perceived, as he supposed, considerable annual displacements in Vega,
Aldebaran, Sirius, and Procyon; the truth being that his instruments
were worn out with constant use, and could no longer be depended
upon.[67] His countryman, Calandrelli, was similarly deluded. The
celebrated controversy between the Astronomer Royal and Dr. Brinkley,
Director of the Dublin College Observatory, turned on the same subject.
Brinkley, who was in possession of a first-rate meridian-circle,
believed himself to have discovered relatively large parallaxes for four
of the brightest stars; Pond, relying on the testimony of the Greenwich
instruments, asserted their nullity. The dispute, protracted for
fourteen years, from 1810 until 1824, was brought to no definite
conclusion; but the