ClipArt ETC
"The most simple refracting telescope consists of a tube, containing two convex lenses, the one having a long, and the other a short, focal distance." -Comstock 1850

Refracting Telescope

"The most simple refracting telescope consists of a tube, containing two convex lenses, the one having…

"Suppose the object o to be at such a distance, that the rays of light from it pass in parallel lines, p, p, to the great reflector, r, r. this reflector being concave, the rays are converged by reflection, and cross each other at a, b which the image is inverted. The rays then pass to the small mirror, b, which being also concave, they are thrown back in nearly parallel lines, and having passed the aperture in the centre of the great mirror, fall on the plano-convex lens e." -Comstock 1850

Refracting Telescope

"Suppose the object o to be at such a distance, that the rays of light from it pass in parallel lines,…

"Diagrams illustrating two stages in the development of the vertebrate eye. A, showing the relation of the ectoderm, the brain vesicle, and the optic vesicle. The right side of the figure shows a later stage than the left. B, later stage, showing the lens, eye-ball and retina in position. b.v., brain vesicle formed by the invagination oof the ectoderm (ect.); l, lens; mes., mesodermal tissue; o.n., optic nerve; o.s., optic stalk; o.v., optic vesicle, a portion of the brain vesicle; r, retinal layer; v.h., interior of eye-ball which comes to contain the vitreous humor." — Galloway

Vertebrate Eye

"Diagrams illustrating two stages in the development of the vertebrate eye. A, showing the relation…