1 degree subtends, at a distance of 1 statute mile, 90 feet.
1' subtends, at a distance of 1 statute mile, 18 inches.
1' subtends at a distance of 100 yards, 1 inch.
1" of latitude on the earth's surface is 100 feet.
30' is subtended by the diameter of either the sun or the moon.

Angles measured by their Chords.--The number of degrees contained by any
given angle, may be ascertained without a protractor or other angular
instrument, by means of a Table of Chords. So, also, may any required
angle be protracted on paper, through the same simple means. In the first
instance, draw a circle on paper with its centre at the apex of the angle
and with a radius of 1000, next measure the distance between the points
where the circle is cut by the two lines that enclose the angle. Lastly
look for that distance (which is the chord of the angle) in the annexed
table, where the corresponding number of degrees will be found, where the
corresponding number of degrees will be found. If it be desired to
protract a given angle, the same operation is to be performed in a
converse sense. I need hardly mention that the chord of an angle is the
same thing as twice the sine of half that angle; but as tables of natural
sines are not now-a-days commonly to be met with, I have thought it well
worth while to give a Table of Chords. When a traveller, who is
unprovided with regular instruments, wishes to triangulate, or when
having taken some bearings but having no protractor, he wishes to lay
them down upon his map, this little table will prove of very great
service to him. (See "Measurement of distances to inaccessible places.")

[Table of Chords to Radius of 1000].

Triangulation.--Measurement of distance to an inaccessible place.--By
similar triangles.--To show how the breadth of a river may be measured