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 treats of Optics. Reasoning will be able to conclude nothing else but this, that the orb of Venus turns on its own axis with an exceedingly swift rotation, displaying one after another different parts of its surface which are more or less capable of retaining the sun's light.

But enough of my own conclusions. Let us now hear as an epilogue Galileo's conclusions built up out of all the observations which he has made with his telescope, and announced from time to time. Thus he writes once more:—

"Illustrissimo e Reverendissimo Signore mio colendissimo.

"IIoHo [sic]	ricevuto gusto, e contento particolarissimo nella lettura dell' ultima di Vostra Signoria Illustrissima e Reverendissima delli 7 stante, ed in particolare in quella parte dove ella m'accenna la favorevole inclinazione dell' Illustriss. Sig. Cons. Wackher, verso