[I] See p. 59.
[J] _See our_ Author's Lect. Optic. _Part_ II. _Sect._ II. _p._ 239.
[K] _As is done in our_ Author's Lect. Optic. _Part_ I. _Sect._ III.
_and_ IV. _and Part_ II. _Sect._ II.
[L] _See our_ Author's Lect. Optic. _Part_ II. _Sect._ II. _pag._ 269,
&c.
[M] _This is demonstrated in our_ Author's Lect. Optic. _Part_ I.
_Sect._ IV. _Prop._ 35 _and_ 36.