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reclamation of land

(Encyclopedia)reclamation of land, practice of converting land deemed unproductive into arable land by such methods as irrigation, drainage, flood control, altering the texture and mineral and organic content of so...

depth charge

(Encyclopedia)depth charge, explosive device used against submarines and other underwater targets, either rolled into the water from rails on the stern of a ship or propelled from depth charge throwers. The charge ...

aquaponics

(Encyclopedia)aquaponics, the growing of plants and the raising of fish by combining aquaculture with the techniques of hydroponics, usually on a small scale. Water containing fish waste matter is used as the nutri...

McNary Dam

(Encyclopedia)McNary Dam, 7,265 ft (2,214 m) long and 183 ft (56 m) high, on the Columbia River between Oregon and Washington, near Umatilla, Oreg.; built 1947–56 by the U.S. Corps of Engineers. Located at the he...

Minnehaha Falls

(Encyclopedia)Minnehaha Falls mĭnˌēhäˈhä [key] [laughing water], 53 ft (16.1 m) high, SE Minn., in Minnehaha Creek, which flows from Lake Minnetonka (23 sq mi/60 sq km) SE to the Mississippi River. The surrou...

Archimedes' screw

(Encyclopedia)Archimedes' screw, a simple mechanical device believed to have been invented by Archimedes in the 3d cent. b.c. It consists of a cylinder inside of which a continuous screw, extending the length of th...

Savery, Thomas

(Encyclopedia)Savery, Thomas, c.1650–1715, English engineer. He became a military engineer, rising to the rank of captain by 1702. He spent his free time performing experiments in mechanics, inventing such device...

cupric sulfate

(Encyclopedia)cupric sulfate ko͞oˈprĭk sŭlˈfāt, kyo͞oˈ– [key] or copper (II) sulfate, chemical compound, CuSO4, taking the form of white rhombohedral crystals or amorphous powder. It decomposes at 650℃ ...

hydroponics

(Encyclopedia)hydroponics, growing of plants without soil in water to which nutrients have been added. Hydroponics has been used for over a century as a research technique, but not until 1929 were experiments condu...

Amu Darya

(Encyclopedia)Amu Darya or Amudarya both: ämo͞oˈ däryäˈ, äˈmo͞o därˈyə [key], river, c.1,600 mi (2,580 km) long, formed by the junction of the Vakhsh and Pandj rivers, which rise in the Pamir Mts. of ce...