[ Illustration: decorative ]
APPENDIX TO Hints on Silvered Glass Reflecting Telescopes.
The object of this pamphlet is to give some new and additional
advice not contained in my “Hints on Silvered Glass Reflecting
Telescopes,” on silvering and adjusting them; and, as the results of
continued and recent experience, it is hoped they may be useful, and
may prove an acceptable appendix to my little book of Hints.
The first thing to do after fastening the mirror to the wooden
support, is to suspend it in the dish in which it is to be silvered,
and so to adjust it that there shall be one inch between the bottom
of the mirror and the bottom of the dish; then pour in water to come
a quarter of an inch up the sides of the glass—the quantity thus
found is to be measured, and will be the exact amount of the bath
when all the solutions are mixed; this will prevent any hitch at an
important moment, and the glass can be immersed without delay or
disturbance.
Next proceed to wash the surface with nitric acid, taking care that
the acid does not run down the sides, as it is not so easily removed
from the fine ground sides as it is from the polished surface. After
gently but thoroughly rubbing the surface, add a little water, and
again go over; then wash all off, and take a large piece of cotton
wool and well sponge the surface and sides with plenty of water, and
suspend in a dish or plate with water in it.