West. East.
As shown in the first cut, the shadows of the moon are of a conical form, and, if the total eclipse existed but an instant, its projection upon the earth would be of a circular form.
But, since the earth revolves upon its axis, different parts are brought into the shadows; and this chart, to represent all that portion of the earth where any eclipse will be visible, has an oblong form.
Also, since the sun appears to rise in one portion of the earth at the same instant when in another portion of the earth it appears to set, this projection exhibits those parts of the earth where the eclipse commences at the instant of sunrise and sunset.
The next engraving is an enlarged representation of a part of the preceding; embracing a large portion of the United States, where a partial eclipse will be visible.
As exhibited in both charts, the southern line of simple contact of the disks of the sun and moon, passes through Florida.
To express the extent of a partial eclipse of either sun or moon, the diameters of each are divided into twelve equal parts, called digits; and the extent of an eclipse at any place upon the earth is said to be a certain number of these digits.