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¶ The 23. Theoreme. The 25. Proposition. If two numbers be in the same proportion the one to the other, that a cube number is to a cube number, and if the first be a cube number, the second al∣so shall be a cube number.
SVppose that two numbers A and B be in the same proportiō the one to the other, that the cube nūber C is vnto the cube number D. And let A be a cube number. Then I say that B also is a cube nūber. For forasmuch as C, D, are cube nūbers, therfore C,* 1.1 D are like solide numbers, wherfore (by the 19. of the eight) betwene
A Corollary added by Flussates.
* 1.2Betwene a square number and a number that is not a square number, falleth not the proportion of one square number to an other. For if the first be a square number, the second also should be a square number which is contrary to the supposition. Likewis•• betwene a cube number, and a number that is no cube number falleth not the propor∣tion of one cube number to an other. For if the first be a cube number, the second also should be a cube number, which is contrary to the supposition, & therfore impossible.