Burlington free press. [volume] (Burlington, Vt.) 1827-1865, 1847-04-23

of his lordship having on one occasion visited an
establishment in London, and there
shown such a knowledge of mechanics, that
The proprietor in his ignorance of whom he was
Offered him situation of some hun
lreds per anniim--a compliment, one can fancy,
which is not likely to be paid to many other
members fthe peerage. Devoted to pursuits
involving mathematical calculations, he has
been pretty constantly engaged, since 1926. in
perfecting the means of telescope observation;
and on this interesting branch of science alone
he is understood to have spent, till the present
time, as much as 100000. Long-coninucd |
and costly as have been these labors they could |
not have realized their present successful re.
Suits unless they had been conducted with most |
impeiturbabe latience and goud-humor, togcth !
er with readiness to have recourse TO new and
hazardous expedients on all occasions of diff
Guilty and defeat. On this account the opera
tons of bis !ord.l.ip more resemble the long md
studous exercises of the old alchemists in their
laboratories, than the proceedings of a modern
man of science and letters
1t would be very long story to tell all that
Lord Rosse has done since he commenced his
labors twenty years ago. and | need therefore
refer only TO the more important steps in his OPP
erations, a slight popular sketch being alone de-
sirable in these pages. His lordship began by
attempting to make telescope, with glass LEM
SEES, of the old and usual kind. A short course
of experiments proved that little good could a
rise from this effort, and he then adopted the
principle ofthe rejecting telescope, an instru.
ment differing considerably from refractng or
lens telescope and of later invention. Sir Isaac
Newton was the first who constructed a tee-
scope ofthis kind, in 1868 and one which he
made in 1872 is still preserved as a curiosity in
the library of the Royal Society. The prnci-
pie of the rejecting telescope is exceedingly
simple At the bottom ofan open tube is lac
ed piece of polished metal of a slightly hol-
lowed or sepherical form. called "A speculum;
and on this. as on a concave mirror. the object
is reflected. The reflection may be ssen direct
ly by looking in at the upper end of the tube; but
as this would partly intercept the rays from the
object, it is customary to cause the reflection OF
the spcculum to fall on a small fiat mirror, pla-
ced ,blluely at the proper focal distance in the
tube and then look in upon that by an eye
glass at The side. The power of rejecting
speculnm depends like that of a lens, on its di-
ameer and degree Of sphericity -; or properly
speaking, its capacity for collecting the rays
which stream from any object. In employing
the exact spherical concavitv, however. there
is always slight confusion of the eye. in con-
sequence Of the centre of the spectrum giving
the image or reflection of the object 1t different
focal distance from the parts at and near the cir
cumfrence. This confusion, which is called
spherical alteration. can be avoided only by
forming the speculum with a parabolic curve
that is. a concavity slightly eliptical or oval ;
but the exceeding difficulty of producing this
figure with mathematical accuracy, may be
judged from the fact. that if two specula o
six feet in diameter the one spherical and tho
other parabolic, were pressed into contact a
the centre, the edges would no. dverge iron
each more than the thousandth part OF an men