[E] This is very fully treated of in our Author's Lect. Optic. Part I. Sect. II.
[F] See our Author's Lect. Optic. Part I. Sect. II. § 29.
[G] This is demonstrated in our Author's Lect. Optic. Part I. Sect. IV. Prop. 37.
[H] How to do this, is shewn in our Author's Lect. Optic. Part I. Sect. IV. Prop. 31.