The text describes the construction and functionality of an early 'camera obscura,' shaped like a sedan chair, used as a visual aid. It elucidates how the internal table can be adjusted for easy access and illustrates the air-system preventing light penetration. Furthermore, it details components allowing parts of the device to move, enhancing operational flexibility.
DESIGN.
II.
Description of the first Camera Obscura.
4. This machine is shaped somewhat like a sedan chair; its top is rounded towards the back, and in front, it is sloped down to half of its height. See the first figure which represents the machine, with the side opposite the door removed, to better show the interior.
5. Inside, the Board A serves as a table: it turns on two iron pegs that enter the wood forming the front of the machine. This table is supported by two small chains, so it can be raised to enter more easily through the side door.
6. On each side, towards the back of the machine, there is a white iron pipe curved towards both ends, as seen in Figure 2. These pipes are placed in the casing inside, each having one end leading into the machine and the other end outside. They allow air to enter without light passing through. These could not be marked in this representation of the machine.
7. At the back of the machine, on the outside, there are four small irons c c, into which slide two wooden rulers D E, approximately three inches wide. Through the top of these two rulers, pass, toward D, two slats holding Board F, which can be moved forward and backward.