ws of planetary
nebulae, Burnham's and Hussey's hair's-breadth star-splitting operations,
Keeler's measurements of nebular radial motion, Barnard's detections and
prolonged pursuit of faint comets, his discovery of Jupiter's tiny moon,
Campbell's spectroscopic determinations--all this could only have been
accomplished, even by an exceptionally able and energetic staff, with
the aid of an instrument of high power and quality. But there was
another condition which should not be overlooked.

The best telescope may be crippled by a bad situation. The larger it is,
indeed, the more helpless is it to cope with atmospheric troubles. These
are the worst plagues of all those that afflict the astronomer. No
mechanical skill avails to neutralise or alleviate them. They augment
with each increase of aperture; they grow with the magnifying powers
applied. The rays from the heavenly bodies, when they can penetrate the
cloud-veils that too often bar their path, reach us in an enfeebled,
scattered, and disturbed condition. Hence the twinkling of stars, the
"boiling" effects at the edges of sun, moon, and planets; hence
distortions of bright, effacements of feeble telescopic images; hence,
too, the paucity of the results obtained with many powerful
light-gathering machines.

No sooner had the Parsonstown telescope been built than it became
obvious that the limit of profitable augmentation of size had, under
climatic conditions at all nearly resembling those prevailing there,
been reached, if not overpassed; and Lord Rosse himself was foremost to
discern the need of pausing to look round the world for a clearer and
stiller air than was to be found within the bounds of the United
Kingdom. With this express object Mr. Lassell transported his 2-foot
Newtonian to Malta in 1852, and mounted there, in 1860, a similar
instrument of fourfold capacity, with which, in the course of about two
years, 600 new nebulae were discovered. Professor Piazzi Smyth's
experiences during a trip to the Peak of Teneriffe in 1856 in search of
astronomical opportunities[1638] gave countenance to the most sanguine
hopes of deliverance, at suitable elevated stations, from some of the
oppressive conditions of low-level star-gazing; yet for a number of
years nothing effectual was done for their realisation. Now, at last,
however, mountain observatories are not only an admitted necessity but
an accomplished fact; and Newton's long forecast of a time when
astronomers w