The word means "light drawing." It is a mode of fixing on certain
substances the lights and shades of any object by means of a lens
inserted in a camera obscura. This process was first called
Daguerreotype from the name of the inventor, Daguerre. A plate of
copper thinly coated with silver is exposed to the vapor of iodine,
then placed in a camera obscura, where an image of the object to be
presented through a lens is cast upon it. Ambrotype is the same
application to glass. There are now different variations of method in
the use of the same agents. Now photography consists in taking the
images on what is called a negative--that is, a glass coated with a
silvered collodion (gun-cotton dissolved in alcohol and ether) film.
From this plate another image is taken on silvered paper, which we
call the positive image. There are also other chemicals used instead
of silver.


What is a Camera Obscura?

A small box or dark room into which the light is admitted through a
lens.


What is a Stereoscope?

It is an instrument exhibiting the effects and advantages of seeing
with two eyes. The instrument is so constructed that from a flat
picture we may see the solid body in its reality in nature.


What is a Kaleidoscope?