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Plate Face Down: Beside the production of etched plates, Niepce used his bitumen process for making direct positives on metal and also glass plates. After exposure he washed the bitumen-coated plate in his solvent, which laid bare the plate in those parts where little light had fallen. He now put the plate face down on top of an open box containing iodine. This element becomes gaseous at room temperature, and the fumes darkened the plate in the shadowy areas.
If the initial clash involves a fast-moving continental plate, the folds may be thrown even higher forming much larger mountain ranges. A continental plate thrust under another tends to maintain an upward pressure, rather like a submerged cork seeking to regain the surface: in time the stationary plate is levered upwards and the attached fold mountains move with the plate. The Himalayas were formed when the northern edge of the Indian continental plate collided with and slid under the Asian plate; the Asian plate was then lifted and the world's highest mountain range was created.
Plate Glass. Louis Lucas invented the system of casting plate glass in France in 1688, and for years that country's glass workers produced the world's finest plate glass. The next important step in that field was made by Max Bicheroux, a German, who developed a machine for rolling plate glass. It was perfected shortly after World War I. |
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