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"Camera obscura strictly signifies a darkened chamber, because the room must be darkened, in order to observe its effects. To witness the phenomena of this instrument, let a room be closed in every direction, so as to exclude the light. Then from an aperture, say of an inch in diameter, admit a single beam of light, and the images of external things, such as trees and houses, and persons walking the streets, will be seen inverted on the wall opposite to where the light is admitted, or on a screen of white paper, placed before the aperture. The reason why the image is inverted will be obvious, when it is remembered that the rays proceeding from the extremities of the object must converge in order to pass through the small aperture; and as the rays of light always proceed in straight lines, they must cross each other at the point of admission. Thus the pencil a, coming from the upperpart of the tower, and proceeding straight, will represent the image of the part at b, while the lower part c, for the same reason, will be represented at d." —Comstock, 1850

Camera Obscura

"Camera obscura strictly signifies a darkened chamber, because the room must be darkened, in order to…

"Camera obscura strictly signifies a darkened chamber, because the room must be darkened, in order to observe its effects. To witness the phenomena of this instrument, let a room be closed in every direction, so as to exclude the light. Then from an aperture, say of an inch in diameter, admit a single beam of light, and the images of external things, such as trees and houses, and persons walking the streets, will be seen inverted on the wall opposite to where the light is admitted, or on a screen of white paper, placed before the aperture. The reason why the image is inverted will be obvious, when it is remembered that the rays proceeding from the extremities of the object must converge in order to pass through the small aperture; and as the rays of light always proceed in straight lines, they must cross each other at the point of admission. Thus the pencil a, coming from the upperpart of the tower, and proceeding straight, will represent the image of the part at b, while the lower part c, for the same reason, will be represented at d." —Comstock, 1850

Camera Obscura

"Camera obscura strictly signifies a darkened chamber, because the room must be darkened, in order to…

"The compasses, next to the T square and triangles, are used more than any other instrument. A pencil and pen point are provided, either of which may be inserted into a socket in one leg of the instrument, for the drawing of circles in pencil or ink." — Hallock, 1905

Compasses

"The compasses, next to the T square and triangles, are used more than any other instrument. A pencil…

"The compasses, next to the T square and triangles, are used more than any other instrument. A pencil and pen point are provided, either of which may be inserted into a socket in one leg of the instrument, for the drawing of circles in pencil or ink." — Hallock, 1905

Compasses

"The compasses, next to the T square and triangles, are used more than any other instrument. A pencil…

"The compasses, next to the T square and triangles, are used more than any other instrument. A pencil and pen point are provided, either of which may be inserted into a socket in one leg of the instrument, for the drawing of circles in pencil or ink." — Hallock, 1905

Compasses

"The compasses, next to the T square and triangles, are used more than any other instrument. A pencil…

"The compasses, next to the T square and triangles, are used more than any other instrument. A pencil and pen point are provided, either of which may be inserted into a socket in one leg of the instrument, for the drawing of circles in pencil or ink." — Hallock, 1905

Compasses

"The compasses, next to the T square and triangles, are used more than any other instrument. A pencil…

"The compasses, next to the T square and triangles, are used more than any other instrument. A pencil and pen point are provided, either of which may be inserted into a socket in one leg of the instrument, for the drawing of circles in pencil or ink." — Hallock, 1905

Compasses

"The compasses, next to the T square and triangles, are used more than any other instrument. A pencil…

"The compasses, next to the T square and triangles, are used more than any other instrument. A pencil and pen point are provided, either of which may be inserted into a socket in one leg of the instrument, for the drawing of circles in pencil or ink." — Hallock, 1905

Compasses

"The compasses, next to the T square and triangles, are used more than any other instrument. A pencil…

A pencil sharpened in a conical point. Conical points will wear away faster than a wedge or flat point.

Conical Point of Pencil

A pencil sharpened in a conical point. Conical points will wear away faster than a wedge or flat point.

Side view of a hand drawing on a mechanical drawing board.

Hand Drawing

Side view of a hand drawing on a mechanical drawing board.

An illustration of a young girl holding a pen.

Girl Holding Pen

An illustration of a young girl holding a pen.

Hand writing with pencil.

Hand

Hand writing with pencil.

An illustration of a hand holding a pen.

Hand Holding Pen

An illustration of a hand holding a pen.

Hand holding pencil

Hand holding pencil

Hand holding pencil

All lines in a mechanical drawing are made with the aid of an instrument. Horizontal lines are drawn with the upper edge of the T-square blade as a guide.

Drawing a Horizontal Line

All lines in a mechanical drawing are made with the aid of an instrument. Horizontal lines are drawn…

"Curves other than arcs of circles are drawn with the pencil or ruling pen by means of curved or irregular-shaped rulers, called irregular curves. A series of points is first determined through which the curved line is to pass. The line is then drawn through these points by using such parts of the irregular curve as will pass through several of the points at once, the curve being shifted from time to time as required." — Hallock, 1905

Irregular Curves

"Curves other than arcs of circles are drawn with the pencil or ruling pen by means of curved or irregular-shaped…

A form of pen used for drawing lines of even thickness. It commonly consists of two blades which hold ink between them. The distance apart of the points being adjusted by a screw to conform to the desired width of the line.

Ruling Pen

A form of pen used for drawing lines of even thickness. It commonly consists of two blades which hold…

Sharpened drawing pencil for mechanical drawings.

Drawing Pencil

Sharpened drawing pencil for mechanical drawings.

An illustration of two pencils, one long and one short.

Long & Short Pencils

An illustration of two pencils, one long and one short.

"These pencils of rays not only flow from the points designated in the figure, but in the same manner from every other point on the surface of a visible object." -Comstock 1850

Pencils of Rays

"These pencils of rays not only flow from the points designated in the figure, but in the same manner…

Sharpen the the pencil by removing the wood with a penknife and rubbing the lead on sand paper. The wedge or flat point will remain sharper than the conical point.

Wedge Point of Pencil

Sharpen the the pencil by removing the wood with a penknife and rubbing the lead on sand paper. The…