Miscellaneous Intelligence. 435 
it be desired to observe through all azimuths and altitudes, the whole 
arrangement, including the telescope, can be made to revolve horizon- 
tally. Doubtless an equatorial mounting could be contrived, but I doubt 
if it could be made convenient. 
The large ring webld maanirally be composed of segments, which 
could be cast in speculum metal, and polished by a revolving straight 
e 
glass, cut into shape while plane, and bent, when heated, to the re-, 
quired curvature by a mould. Then a final polishing, and a pure silver. 
It is, pe erhaps, superfluous to dwell longer on this arrangement. I 
would say, in conclusion, that if an extension of telescopic power much 
felted reflection, exceeding in intensity anything ever rea ized. 
In transit or other meridian instruments, it is now necessary for 
the hote telescope to turn in its axis, and for the observer to follow 
its rotation with much discomfort and torture of timb. ‘There is a very 
simple mode of Rd daslite with all this, which occurred to Prof. Bache 
and myself, het rae ntly and nearly "LO REE It has not yet 
been tried, and I know not when it will 
Let the telescope be supported in any manner, with its axis horizon- 
tal and perpendicular to the meridian. Mount at its object-glass end a 
perfectly plane mirror, making an angle of 45° with the line of colli- 
mation, and ae for this a rotation measured on a meridian limb. 
is 
= 
3 
ic} 
= 
=) 
172) 
8 
oO 
2) 
eS 
- 
=" 
oO 
oO 
eee 
& 
o 
im] 
: 
= 
a) 
=| 
99 
nm 
nn 
@ 
pom 
ee 
5 
wg 
oO 
=. 
@ 
= ¢ 
—~ 
h 
with no other hotel ita that of the mirror rotation. This mirror may 
be made a permanent appendage to the object- -glass, or may be mount- 
ed quite itself. The main difficulty would be in the first adjustment, 
and the setting up would then probably be easier than that of the ex- 
isting fesse: 
eans of arranging this so as to get the ae ae of glass, 
ce 
can be formed hte eflect 93 per cent. of the incident light at 45°, 
rd 
The el S eneee art is surely so perfect in the Coast Survey 
Laboratory, that silver mirrors can be deposited ona speculum metal 
matrix, leaving only a final polish to be given. It is not rash to assume 
ttempt. 
h whole, the introduction of this reflector, and the 
consequent ’ revolutionizing of the transit, will prove desirable in prac- 
tice, remains to be seen. 
= 
= 
ES 
