He further discovered that oil of cassia had a different power of refraction from water, and the white of an egg still a different power.

He discovered also that the first lens of the eye, the aqueous humor, is very like water; that the crystalline lens is a firm jelly, and that the vitreous humor is about the consistency of the white of an egg.

The combination of these three lenses, of different powers of refraction, secures the correction of their separate errors.
He could not make telescope lenses of jelly, nor water; therefore, he could not make a perfect achromatic telescope, but he learned the lesson of mutual compensations of difficulties which the Maker of the eye teaches the reflecting anatomist, and procuring flint and crown glass of different degrees of refraction, he arranged them in the achromatic lens so as nearly to remedy the defect.
I think that you will at once admit that Dolland's attempt to remedy the evils of confused sight in the telescope indicated a desire to obtain a precise and correct view of the objects; and that his success in constructing an instrument, nearly perfect, for the use of astronomers, gave evidence that he himself had a clear idea of that perfect and accurate vision which he thus attempted to bestow on them.

Shall we then imagine any inaccuracy in the sight of Him, who not only desired, but executed and bestowed on us, an instrument so perfectly adapted to the imperfections of this lower world, and whose very imperfections are the materials from which he produces clear and perfect vision?
No! in God's eye there are no chromatic refractions of passions, or prejudice, or party feeling, or self-love.

He sees no reflected or refracted light.