"Professor Swan's Designs.—Among several ingenious arrangements and new forms of agents proposed by Professor Swan is the mode of sending rays from prisms through interstices left between other prisms placed in front, and also a form of agent which he termed the triesoptric prism, in which the rays would undergo two refractions and three reflexions. a are the front and b the triesoptric prisms. The two upper and lower prisms a are constructed of flint glass of high refractive power. It will be observed from the drawing that this ingenious arrangement is nevertheless open to objection, for cones of light of 30 degrees in front and of 65 degrees at the back are lost through the interstices." —The Encyclopedia Britannica, 1910

Swans Designs

"Professor Swan's Designs.—Among several ingenious arrangements and new forms of agents proposed…

"Suppose a, to be a distinct object, from which pencils of rays flow from every point toward the object lens b. The image of a, in consequence of the refraction of the rays by the object lens, is inverted at c, which is the focus of the eyeglass d, and through which the image is then seen, still inverted." -Comstock 1850

Refracting Telescope

"Suppose a, to be a distinct object, from which pencils of rays flow from every point toward the object…

A burner that mixes air and gas to produce a very hot flame

Electric Torch

A burner that mixes air and gas to produce a very hot flame

Blowtorch: a burner that mixes air and gas to produce a very hot flame

Flame Torch

Blowtorch: a burner that mixes air and gas to produce a very hot flame

"On ancient monuments, the torch appears to be formed of wooden staves or twigs, either bound by a rope drawn round them in a spiral form, or surrounded by circular bands at equal distances." — Anthon, 1891

Torches

"On ancient monuments, the torch appears to be formed of wooden staves or twigs, either bound by a rope…

"Condensing Twin Prism Light.—Part of the Lamiash light in the Firth of Clyde. Its action will be easily understood by the numbers shown on the diagram." —The Encyclopedia Britannica, 1910

Twin Prism

"Condensing Twin Prism Light.—Part of the Lamiash light in the Firth of Clyde. Its action will…

"Showing diagrammatically one explanation of the production of light waves by revolving electrons." —Croft 1917

Light Waves Explanation

"Showing diagrammatically one explanation of the production of light waves by revolving electrons."…

"Diagram indicating one explanation which has been advanced for light and heat waves generated by the movement of an electron around its orbit in a molecule and by the simultaneous movement of the molecule." —Croft 1917

Light Waves

"Diagram indicating one explanation which has been advanced for light and heat waves generated by the…