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Updated: May 2, 2025
He thought out a plan by which he could place pieces of glass in a tube, and bring the stars close to the earth. By daylight the whole plan was clear in his mind, and he hastened to the shop of the glassmakers. There, two lenses were made, one plano-convex, and the other plano-concave, and these were placed in a tube made of sheet copper.
For a telescope which has no micrometer, the Huyghenian or negative eye-piece, as it is commonly called, is the best. As made by Huyghens, it consists of two plano-convex lenses, with their plane sides next the eye, as shown in the figure. So far as we have yet described our telescope it is optically complete.
Bricks still plano-convex; stamped inscriptions begin. Stone maceheads of same type as earlier. Not many mounds of this period have been dug. Characteristics. Very high development. Bitumen still used for mortar. With the bodies are found large numbers of agate and cornelian beads, unpolished. IV. LATER BRONZE AGE: Kassite, Middle Babylonian, and Early Assyrian periods; c. 1800- 1000 B.C.
All of its transparent portions are directly concerned in this work, and the portions that are not transparent serve to protect and operate these parts and hold them in place. Of chief importance are the crystalline lens and the cornea. Both of these are lenses. The cornea with its inclosed liquid is a plano-convex lens, while the crystalline lens is double convex.
In a lighthouse on the dioptric system, the lantern is constructed with eight sides, which form an octagonal prism around the lamp in the centre. The centre of each side is occupied by a plano-convex lens, something similar to a burning-glass, having a diameter of about fifteen inches. This central lens is not sufficient to cover the entire side.
The burials are hard to distinguish from similar contracted interments of later date, except that the furniture is more abundant in early times and mat graves are unusual in later days Mounds of this age may be known by the occurrence on the surface of scraps of oxydized copper, nails, &c.; shell-fragments; undecorated light drab sherds; and the typical small plano-convex bricks. Characteristics.
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