410 
NATORE 
[ Feb. 17, 1870 
is 32 feet, and it is of a cigar shape ; the diameter at the 
object-end being 27 inches, and at the centre of the tube 
34 inches. The cast-iron pillar supporting the whole is 
29 feet in height from the ground to the centre of the 
declination axis, when horizontal ; and the base of it is 
5 feet 9 inches in diameter. The trough for the polar axis 
alone weighs 24 cwt., the weight of the whole instrument 
being nearly 9 tons. 
The tube is constructed of steel plates rivetted together, 
and is made in five lengths, screwed together with bolts 
and flanges. The plates of the central length are one- 
eighth of an inch thick, and those of each end one- 
sixteenth thick, so as to reduce the weight of the ends 
as much as possible, and avoid flexure. 
Inside the outer tube are five other tubes of zinc, in- 
creasing in diameter from the eye to the object-end : the 
wide end of each zinc tube overlapping the narrow end of 
the following tube, and leaving an annular space of about 
an inch in width round the end of each for the purpose of 
ventilating the tube, and preventing, as much as possible, 
all interference by currents of warm air, with the cone of 
rays. The zinc tubes are also made to act as dia- 
phragms. 
The object-glass has an aperture of 25 inches (nearly), 
and in order as much as possible to avoid flexure from 
unequal pressure on the cell, it is made to rest upon three 
fixed points in its cell, and between each of these points 
are arranged three levers and counterpoises round a 
counter-cell, which act through the cell direct on to the 
glass, so that its weight in all positions is equally distri- 
buted among the 12 points of support, with a slight excess 
upon the three fixed ones. The focal length of the lens 
is 29 feet. A Barlow lens is arranged to slide on a brass 
framework within the tube. The hand is passed through 
an opening in the side of the tube, and by means of a 
handle attached to the cell, the lens may be pushed into or 
out of the cone of rays. 
Attached to the eye-end of the tube are two finders, 
each 4 inches aperture ; they are fixed above and below 
the eye-end of the main tube, so that one may be readily 
accessible in all positions of the instrument. It is also 
supplied with a telescope having an 0. G. of 6}”.. This is 
fixed between the two finders, and is for the purpose of 
assisting in the observations of comets and other objects 
for which the large instrument is not so suitable. This 
assistant telescope is provided with a rough position 
circle and micrometer eye-pieces, and is illuminated by 
new apparatus lately described in NATURE. 
Two reading microscopes for the declination circle are 
brought down to the eye-end of the main tube ; the circle 
—38 inches in diameter—is divided on its face, and read 
by means of the microscopes and prisms. 
The slow motions in declination and R. A. are given by 
means of tangent screws, carrying grooved pulleys, over 
which pass endless cords brought to the eye-end. 
The declination clamping handle is also at the eye-end. 
The clock for driving this monster telescope is in the 
upper part of the pillar, and is of comparatively small 
proportions, the instrument being so nicely counterpoised 
that a very slight power is required to be exerted by the 
clock, through the tangent screw, on the driving wheel 
(seven feet diameter), in order to give the necessary 
equatorial motion. 
The declination axis is of peculiar construction, necessi- 
tated by the weight of the tubes and their fittings, and 
corresponding counterpoises on the other end, tending to 
cause flexure of the axis. This difficulty is entirely over- 
come by making the axis hollow, and passing a strong 
iron lever through it, having its fulcrum immediately over 
the bearing of the axis near the main tube, and acting 
upon a strong iron plate rigidly fixed as near the centre 
of the tube as possible, clear of the cone of rays. This 
lever, taking nearly the whole weight of the tubes, &c., 
off the axis, frees it from all liability to bend. 
The weight of the polar axis on its upper bearing is 
relieved by friction rollers and weighted levers ; the lower 
end of the axis is conical, and there is a corresponding 
conical surface on the lower end of the trough; between 
these two surfaces are three conical rollers carried by a 
loose or “live” ring, which adjust themselves to equalise 
the pressure. 
The hour circle on the bottom of the polar axis is 26 
inches in diameter, and is divided on the edge,* and read 
roughly from the floor by means of a small diagonal 
telescope attached to the pillar; a rough motion in R.A. 
by hand is also arranged for by a system of cog-wheels 
moved by a grooved wheel and endless cord at the lower 
end of the polar axis, so as to enable the observer to set 
the instrument roughly in R.A. by the aid of the diagonal 
telescope. 
The declination and hour circles will probably be 
illuminated by means of Geissler tubes, and the dark and 
bright field illuminations for the micrometers will be 
effected by the same means, 
Mr. Newall, after the preliminary testing of this magni- 
ficent instrument at his own residence, purposes to erect 
it in some climate favourable for astronomical obser- 
vation. It is very unfortunate that this means in other 
words that the telescope cannot remain in England. 
It is or should be among the things generally known 
that every increase in the size of an object-glass or 
mirror increases the perturbating effects of the atmosphere, 
so that the larger the telescope, the purer must be the air, 
In the absence of this latter condition, a “big” telescope is 
a “big evil,” and skilled’ observers, mindful of this, reduce 
the apertures of their instruments when the air is not 
good. 
We may regard this telescope as a clear gain to English 
science, for Mr. Newall with princely liberality has ex- 
pressed his intention of allowing observers with a special 
research on hand to have the use of the instrument during 
certain regulated hours, 
The observatory, of which we also give a sketch, is 
nearly 50 feet in diameter, and notwithstanding the 
enormous weight of the dome, like the telescope, it is 
easily moved into any required position. 
When complete it will have attached to it a transit- 
room and the observer’s dwelling. And this reminds us 
that Mr. Marth, so well known for his good work done at 
Malta with the Lassell Reflector and elsewhere will have 
charge of this noble instrument of research, 
NOTES 
THE anniversary meeting of the Geological Society takes 
place to-morrow, when Professor Huxley will deliver his address, 
which, it is expected, will be of great scientific interest. The 
Wollaston Medal of the society has this year been awarded to 
the eminent French Malacologist, M. Deshayes, professor at the 
Musée d’ Histoire Naturelle, and the proceeds of the Wollaston 
fund have been awarded to M. Marie Roualt, who, though in 
humble circumstances, has contributed largely to the advance of 
the paleontology of France. The choice of president for the 
coming year has fallen on Mr. J. Prestwich—a choice which will 
be hailed on all sides with the liveliest satisfaction. 
In reply to an address of last Session, Her Majesty has made 
known to the House of Commons that she will give directions 
for the carrying out of the arrangements necessary for observing 
the transit of Venus, which will take place in the year 1874. 
THE Rey. Charles Pritchard, of St. John’s College, Cambridge, 
has been elected to the Savilian Professorship of Astronomy, as 
successor of the late Professor Donkin, Astronomers may con- 
gratulate themselves on this appointment, as Mr. Pritchard’s 
teaching powers are of the first order, the interest he takes in 
* The hour circle is also divided on its face, and read by micrometer 
microscopes. 
= a? 
