An 18th century diagram of a solar eclipse, showing the principles behind them. Figure I shows difference in appearance between total (B) and annular (A) eclipses. Figure II shows how the Moon (small circle, center right) prevents the light (lines) from the Sun (far left) from reaching the Earth (right), when the Moon is situated between the Earth and the Sun. Figure III shows how the position of the Moon (black circles), as viewed from different latitudes, affects the appearance of the Sun during a solar eclipse. Figure IV shows the path of the moon (small circle) in front of the Earth (large circle). This diagram is taken from Astronomy explained upon Sir Isaac Newton's Principles, published by James Ferguson (1710-1776) in 1756.