SPECULA OE REELECTING TELESCOPES. 
315 
A well-fitting, but not tight, tin cover, which may be removed and replaced when the 
speculum is in the tube through a slit in its side, is all the protection' the mirror 
requires ; but it is desirable that there should be a light wooden cover hinged so as to 
fall over this opening when the telescope is in use, to prevent any drop of moisture 
falling from the roof from reaching the speculum. This is all the protection I give my 
mirrors, and I have never found them tarnish. I have tried quicklime, but found it to 
be quite unnecessary, and, besides, an intolerable nuisance. 
I may add, finally, that I shall rejoice if I have succeeded in my endeavour to describe 
this' interesting process so that any person of ordinary intelligence, and not quite 
unacquainted with mechanics, may succeed in producing, without difficulty, surfaces of 
at least a very high degree of perfection. 
