Notes
In our Author's Lectiones Opticæ, Part I. Sect. IV. Prop 29, 30, there is an elegant Method of determining these Foci; not only in spherical Surfaces, but likewise in any other curved Figure whatever: And in Prop. 32, 33, the same thing is done for any Ray lying out of the Axis.
Ibid. Prop. 34.
See our Author's Lectiones Opticæ § 10. Sect. II. § 29. and Sect. III. Prop. 25.
See our Author's Lectiones Opticæ, Part. I. Sect. 1. §5.
This is very fully treated of in our Author's Lect. Optic. Part I. Sect. II.