Year: 1868




The London Guardian, speaking Of the
great telescope of the late Lord Rosse,
tells how it was made


Lord Roses speculum is six feet in
diameter, and its local distance, that is to
say, the distance Of the point at which
the reflected image is formcd--is fifty
three feet. This necessitates a wooden
tube Of rather more than that length, and
at least seven feet in diameter. Let the
reader figure the difficulty Of suspending
such tube heavily weighted at one ex.
tremity with four tons of metal cast into
the shape Of mirror, provided at the
upper end with the movable galleries for
the observers, and the whole capable Of
smooth though limited motion, and he
will have sorae notion of the larger part
of the problem which Lord Rose had to
solve. For by far the most difficult part
was the casting and polishing Of the mir
ror itself. These four tons Of tin and
copper, mingled in definite proportions,
had to be cast into the shape Of an exact
paraboloid, and the whole surface raised
afterwards to faultless polish. Three
huge iron crucibles in the three separate
furnaces held these vast masses of fusing
metal, which, after three hours exposure
to the heat, were lifted out by huge
cranes and poured into the carefully pre-
pared mould.


The spectacle of that casting must
have been sight fit only TO be described
in the Song Of the Bell 1t took place
at night. 'Abovc'-we quote from Mr.
Yields description in his Vacations in
Ireland'-the sky crowded with stars,
seemed to look down conspicuously upon
the work below the furnaces poured out
huge columns of nearly mono chromatic
yellow flames; and the ignited crucibles,
during their passage through the air,
were fountains of red light, producing
on the towers Of the castle such accidents
of color and shade as might almost trans
port to the realms Of enchantment. And
when the crucibles discharged their seeth-
ing coatcnts, for several minutes the met
al rolled in heavy waves like those of
melting quicksilver, and broke IN a surf
of fire on the sides of the mould


"This, however, was only the first pre-
cess. For sixteen weeks the moulded
metal was left in the annealing oven, and
when il was Withdrawn il had still to IN
dergo the delicate and hazardous opera
ton of grinding and polishing. These
were successfully effected by q small
steam engine, initiating with the utmost
nicely the light touch of the human hand
the only instrument which had hitherto
been thought capable of this work. Not
even yet, however, had the speculum
passed all its dangers. The construction
OF which was to support it was problem
of no small difficulty. The slightest
strain or Texture Asuficicnt 10 distort
the image of star. 1t was necessary to
support the speculum by pressure which
should tell with exact equality on every
portion of its surface. 4 most ingenious
contrivauce of a system of triangles, car
rying at their angles eighty-one brass
bells. capable of revolving freely, supplies
this want. On these balls the speculum
reposes with an absolute uniformity Of
pressure, through the changes Of direction
communicated to it By universal joint by
which the whole vast apparatus is con-
nected with its foundation in the earth.
| This is brief sketch of the many
difficulties which had to be overcome and
the many problems which had to be solved
in the construction of this telescope. We
have enumerated them in order that due
need of fame may be assigned to the
genius, perseverance, industry and mum.
fceuce which triumphed over all. AL
this was done By Lord Rosse himself
The powerful and delicate machinery re.
quircd for all these nice and difficult op.
erations was conceived aud matured in his
brain. The workmen who executed il
were trained by his care and worked un
der his own eye. The whole vast expense
was betrayed by his own resources"