About 1760, Mayer, a famous German astronomer and the director of the
observatory of Goettingen, began the publication of a magnificent map of
the Moon, drawn after lunar measurements all rigorously verified by
himself. Unfortunately his death in 1762 interrupted a work which would
have surpassed in accuracy every previous effort of the kind.
Next appears Schroeter of Erfurt (1745-1816), a fine observer (he first
discovered the Lunar _Rills_), but a poor draughtsman: his maps are
therefore of little value. Lohrman of Dresden published in 1838 an
excellent map of the Moon, 15 inches in diameter, accompanied by
descriptive text and several charts of particular portions on a larger
scale.
But this and all other maps were thrown completely into the shade by
Beer and Maedler's famous _Mappa Selenographica_, so often alluded to in
the course of this work. This map, projected orthographically--that is,
one in which all the rays proceeding from the surface to the eye are
supposed to be parallel to each other--gives a reproduction of the lunar
disc exactly as it appears. The representation of the mountains and
plains is therefore correct only in the central portion; elsewhere,
north, south, east, or west, the features, being foreshortened, are
crowded together, and cannot be compared in measurement with those in
the centre.
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