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shifting ; and the operation of the arrangement’ is found to be 
perfect at all altitudes. 
The construction of the tubes, the piers, the mechanism 
of the counterpoises, occupied the remainder of this year and 
the beginning of 1844. In August, a partial polish was given 
to the mirror in order to verify its focal length (which was 
found exactly fifty-four feet) ; and the observing galleries and 
the apparatus for controlling the instrument in right ascension 
were proceeded with. All these gigantic constructions (of 
whose prodigious mass some idea may be formed from the fact 
that they contain, along with their other materials, more than 
one hundred and fifty tons of iron castings), have been exe- 
cuted in Lord Rosse’s workshops, by persons taken from the 
surrounding peasantry, who, under his teaching and training, 
have become accomplished workmen, combining with high 
skill and intelligence the yet more important requisites of 
steady habits and good conduct. It may also be mentioned 
that (such was the clear and definite arrangement of the whole 
in its inventor’s mind) nothing failed from first to last ; and it 
was not necessary for him in any instance to retrace his steps. 
At the beginning of February, 1845, the work being suffi- 
ciently advanced to permit the use of the instrument without 
personal danger, Dr. R. and his friend Sir James South were 
invited to enjoy the trial of it. Its appearance is certainly 
peculiar, and presents a striking contrast to the more compli- 
eated framing of the three-feet telescope which is placed beside 
it. At first sight, one wonders how it is to be moved, for 
nothing attracts notice except the massive piers and the tube; 
but a nearer approach shews that it is the perfection of mecha- 
nical engineering. To have mounted it on the plan of the 
three-feet would have been impracticable as well as useless. 
~The speculum with its supports is seven times the weight of 
that in Herschel’s four-feet, and both on this account, and the 
well-known principle that similar machines are weaker in pro- 
portion to their bulk, such a stand must have been so heavy 
