moon more closely than he could have done with the unaided eye. So far as can be gathered from the mysterious language in which the description of his instrument is wrapped, he made use of magnifying glasses; these do not however seem to have been constructed like a telescope—telescopes were first made about 1600. As LIBRI pointed out (Histoire des Sciences mathematiques III, 101) Fracastoro of Verona (1473-1553) succeeded in magnifying the moon's face by an arrangement of lenses (compare No. 910, note), and this gives probability to Leonardo's invention at a not much earlier date.*
I.
THE EARTH AS A PLANET.
The earth's place in the universe (857. 858).
857.
The equator, the line of the horizon, the ecliptic, the meridian:
These lines are those which in all their parts are equidistant from the centre of the globe.
858.
The earth is