The irregularity of spacing has thus the effect of a convex lens, which accelerates the marginal relatively to the central rays.
Convex spectacles were invented towards the end of the 13th century.
When kept in non-metallic vessels they take the shape of a convex meniscus.
The convex side rests upon the duchy of Coburg and is in part bounded by Bavaria, while the concave side, turned towards the north, contains portions of four other Thuringian states and Prussia between its horns, which are 46 m.
Most of the permeability-temperature curves were more or less convex towards the axis of temperature, and in all the experiments except those with annealed iron and steel wire, the permeability was greatest at the lowest temperature.