THE MOST POWERFUL TELESCOPE IN EXISTENCE. 387 
In days gone by repeated reference was made to the wonderful 
things which could be seen upon the surface of the moon with 
these two giant telescopes of Lord Eosse’s. Picturesque de- 
scriptions were given of the minute features which were visible, 
amazement was often expressed at the small objects which could 
be seen. Still more interesting accounts were given of what 
ought to be visible, — a carpet of pronounced pattern as big as 
Lincoln’s Inn Fields, the Castle at Dublin, the Courthouse at 
Cork, a house, or even a man, provided he were big enough. 
All these ought to be seen if they happened to be on the lower 
surface. Yet when we come to consider what it really is which 
is described as being seen, when we calmly examine the various 
drawings which have been made by the aid of one or the other 
of these great telescopes, then we find that they show nothing 
which cannot be distinctly seen and drawn by the smallest astro- 
nomical telescope of high excellence. An enormous blaze of 
light is gathered by the telescopes, but all this light reveals 
nothing which cannot be seen with far greater ease in a far 
smaller telescope. There are in existence a number of drawings 
of the planets, and observations of their satellites ; there are also 
observations of close double stars, or faint companions to bright 
stars, all made with one or the other of these two telescopes. 
Yet nothing has been seen which is beyond the power of a good 
astronomical telescope of comparatively moderate aperture. It 
is only in observing the dull ill-defined nebulae that Lord Eosse’s 
great telescope has any exceptional advantage, though even in 
this respect it is probably much overrated. As' an astrono- 
mical telescope either of Lord Eosse’s telescopes would be fairly 
beaten by either of the fine eighteen-inch reflectors which are 
now in existence. 
If, then, Lord Eosse’s great telescope is not the most powerful 
in existence, what answer is to be given to the question with 
which we commenced ? Which is the most powerful telescope 
in existence ? There are the great refractors of Pulkova and of 
Cambridge, U.S., each of fifteen inches in diameter and 23 feet 
in focal length. There is the still larger refractor of Chicago 
with an aperture of eighteen inches and a focal length of 23 
feet. All these instruments are of high excellence in defining 
power, the essential point where Lord Eosse’s breaks down. 
There is the reflector of Mr. Lassells, with its metal speculum of 
two feet in diameter and its tube twenty feet in length. There 
is the great Melbourne reflector, with its great metal speculum 
of forty-eight inches in diameter, the second largest telescope 
in the world, but by no means so sharp in definition as might 
be desired, so that it failed to reveal the satellites of Mars which 
were seen with an instrument of not one-sixth the diameter in 
Europe. 
c c 2 
