ct astronomy. Part of their superiority must, indeed, be
attributed to the co-operation of John Bird, who provided Bradley in
1750 with a measuring instrument of till then unequalled excellence. For
not only was the art of observing in the eighteenth century a peculiarly
English art, but the means of observing were furnished almost
exclusively by British artists. John Dollond, the son of a Spitalfields
weaver, invented the achromatic lens in 1758, removing thereby the chief
obstacle to the development of the powers of refracting telescopes;
James Short, of Edinburgh, was without a rival in the construction of
reflectors; the sectors, quadrants, and circles of Graham, Bird,
Ramsden, and Cary were inimitable by Continental workmanship.

Thus practical and theoretical astronomy advanced on parallel lines in
England and France respectively, the improvement of their several
tools--the telescope and the quadrant on the one side, and the calculus
on the other--keeping pace. The whole future of the science seemed to be
theirs. The cessation of interest through a too speedy attainment of the
perfection towards which each spurred the other, appeared to be the only
danger it held in store for them. When all at once, a rival stood by
their side--not, indeed, menacing their progress, but threatening to
absorb their popularity.

The rise of Herschel was the one conspicuous anomaly in the astronomical
history of the eighteenth century. It proved decisive of the course of
events in the nineteenth. It was unexplained by anything that had gone
before; yet all that came after hinged upon it. It gave a new direction
to effort; it lent a fresh impulse to thought. It opened a channel for
the widespread public interest which was gathering towards astronomical
subjects to flow in.

Much of this interest was due to the occurrence of events calculated to
arrest the attention and excite the wonder of the uninitiated. The
predicted return of Halley's comet in 1759 verified, after an
unprecedented fashion, the computations of astronomers. It deprived such
bodies for ever of their portentous character; it ranked them as
denizens of the solar system. Again, the transits of Venus in 1761 and
1769 were the first occurrences of the kind since the awakening of
science to their consequence. Imposing preparations, journeys to remote
and hardly accessible regions, official expeditions, international
communications, all for the purpose of observing them to