SIDEREAL OBSERVATIONS

...will give a clear effect. Furthermore, the large spots original: "maculæ"; Galileo refers to the dark plains we now call 'maria' or seas on the Moon are seen to be lower than the brighter regions; for in both the waxing and the waning Moon, there are always areas of the brighter part adjacent to these large spots that stand out along the boundary of light and shadow the 'terminator' line, as we have observed in drawing the figures. Not only are the boundaries of these spots lower, but they are also more uniform, not interrupted by wrinkles or roughness. The brighter part, however, stands out most prominently near the spots; so much so that, both before the first quadrature the first quarter phase and almost at the second, certain vast elevations rise up both above and below a particular large spot occupying the upper, northern region of the Moon, as the accompanying illustrations display.

The Moon's spots are lower than the bright areas.

The following illustration is one of Galileo's revolutionary engravings, showing the Moon not as a perfect, smooth sphere as previously believed, but as a rugged, mountainous world similar to Earth.