9 They which are reciprocall in base and heighth are equall, 15 p xij.
These are consectaries drawne out of the [16] and [18 e. iiij]. As here you see.
10 A Cylinder is that which is comprehended of a cylindricall surface and the opposite bases.
For here two circles, parallell one to another are the bases of a Cylinder.
Therefore
11 It is made by the turning about of a right angled parallelogramme, the one side standing still. 21. d xj.