The text discusses the use and construction of a portable camera obscura. It highlights the importance of using polished mirrors and the challenges of mirror placement due to humidity. The description includes details on building a box with a curtain and placing lenses for viewing, ensuring minimal light intrusion.
METHOD FOR LEARNING
When possible, the concave mirror is introduced into
the construction of the machine. 2°. When more than
two flat mirrors are used, the rays after a triple reflec-
tion become too weak to well represent the objects;
and it is even necessary when using two mirrors that
they are extremely polished. 3°. The mirrors should not be
inserted into the machine because in such a
confined space, the humidity from respiration would obscure them:
XI.
Another More Portable Darkroom than the Previous Ones.
37. Make a wooden box, one and a half feet wide, two feet
and a few inches long, and about a foot and ten inches high,
or even two feet.
Construct the back BC slanted. The front should
only be closed with a curtain of good black fabric,
capable of preventing light from penetrating the box.
To conveniently attach this curtain, add on the
front of the box a plank cut into a semi-circle,
with a radius of one foot, and whose diameter
will be attached by hinges to the board that forms the
top, and adjust the curtain all around the semi-
circle, as depicted in the figure.
At the top of the box, slightly at the rear,
create an opening into which a telescope tube DE is to be inserted,
equipped at the top D with a convex lens
on both sides, which forms part of a large sphere,
just like the glasses suited for the elderly.
On each side of this opening D, on top
of the box, two brackets should be fixed to hold a small