Dredging
the operation of removing mud, silt and other deposits from the bottom of harbors, canals, rivers, docks, etc., by mechanical means. The steam-dredging machine now in common use is said to have been first applied by Boulton and Watt for use on the Weir at Sunderland, England, in 1796. It has a succession of strong iron buckets on an endless chain running on a frame the lower end of which is vertically adjustable so as to regulate the depth at which it works. The buckets tear up the matter at the bottom, raise it, and discharge it into barges or hoppers stationed close to the dredging vessel. The OSGOOD DIPPER DREDGE dians regarded dreams as prophetic and often took them as solemn injunctions.
Among more enlightened people there may be an inducement to action from the impression of a dream; here also, the consequence is the fulfilment of the phecy. Such were the dreams of Judas Maccabæus, of Sulla, of Germanicus. It is said that the city of Carthage was rebuilt by Augustus Cæsar in consequence of the dream of his uncle Julius. Of such a nature, too, were the dreams of the Emperor Julian and of Calpurnia; and such was the dream of Cromwell that he should be the greatest man in England. In all these, and a thousand more, the mere constant thinking excited the dream. See FREUD, SIGMUND; PSYCHOANALYSIS.
DREBBEL (dreb'bel), CORNELIUS, a Dutch philosopher; born in Alkmaar, Netherlands, in 1572. He invented the Suez Canal was excavated by means of a ladder dredge with a long chute and supporting girder. The material excavated was carried in boxes on a sort of tramway and tipped out on the bank.
The excavating buckets are sometimes placed on the perimeter of a large wheel instead of on an endless chain. The so-called clamshell bucket consists of two parts hinged together which descend through the water open and return closed with its clutch of material amounting sometimes to five cubic yards.
In order to work in clay or hard sand it is provided with teeth. In some cases the current of river or tides has been utilized in dredging channels. In bottoms of mud or loose sand the steam pump or hydraulic dredger may be used.
Great improvements have been made in hydraulic dredges, and some built in recent years for use in the Mississippi DRED SCOTT CASE river have a capacity of over 1,000 cubic yards per hour.
Dredging is also the operation of dragging the bottom of the sea in order ing the bottom of the sea in order to bring up oysters, or to procure shells, plants, and other objects for scientific observation. The oyster dredge is a light iron frame with a scraper like a narrow hoe on one side, and a suspending apparatus on the other. To the frame is attached a bag made of some kind of netting to receive the oysters.
The dredges used by naturalists are mostly modifications of or somewhat similar to the oyster dredge.
DRESDEN embellished by Augustus the Strong ing the 19th century. Among the chief (1694-1736 ), and rapidly increased duredifices besides several of the churches picture-gallery and other treasures; the are the museum containing a famous Japanese Palace (Augusteum), contain- 400,000 volumes, besides a rich collection ing the royal he royal ing the royal library of from 300,000 to to of manuscripts; the Johanneum, containing the collection of porcelain and the historical museum, a valuable collection belonging to the Middle Ages. The royal of arms, armor, domestic utensils , etc., palace contains (in what is called the SHOOT ↓ LADDER BUCKET SUCTION PIPE BUCKET AND SUCTION DREDGE