Page:The American Cyclopædia (1879) Volume VI.djvu/117

 DIKE DILKE 109 and every provision is made of materials that may be required for immediate repairs. Du- ring the winter months watchmen patrol the dikes by day and night, and give alarm when- ever the tide threatens to overflow. The peo- ple then hasten to the point, and with mats of straw and rushes and large sheets of sail cloth buried in the sand they raise a temporary bul- wark, to be more securely built before the ap- proach of the next tide. Dikes constructed as barriers for reservoirs are built on several well established plans. The loose materials exca- vated for the channel or basin are piled up in a firm bank and consolidated by rolling with heavy rollers. Sometimes they are rendered more secure by building within them along their central line a puddle bank of selected clayey earth, mixed with sufficient sand to give it tenacity, so as not to crack in drying. This should be carried down to a solid founda- tion, and may be advantageously bedded upon a layer of concrete. It is built up a little later than the bank on each side of it, and both are rolled on the addition of every layer of six inches with a heavily ribbed roller of cast iron. The use of any material of the nature of quick- sand is to be carefully avoided in any part of the embankment. Next the water it is well to face the work with a layer of broken stone that will pass through a two-inch ring, and over this should be laid a sloping wall of flat stone at an inclination of 1 base to 1 vertical, or from that to one of 3 base to 1 vertical. The broken stone within is a guard against the embankment being penetrated by any small water animals. The dike around the great reservoir of 106 acres in the Central park, New York, is made on the plan given above, which is approved by the engineers of France and England. It is 16 ft. 8 in. wide at top, with an inner and outer slope of 1 base to 1 verti- cal. The puddle bank of clay in the middle, which reaches to within a few feet of the top, is 16 ft. thick. The depth of water around the margin is 34 ft. At the surface of the water the thickness of the embankment is 24 ft. 9 in., and at 30 ft. below it is 114 ft. 9 in. The French engineers give the preference to this mode of construction over that of a wall of masonry alone or of an embankment within a wall. Stonework by settling is liable to injury that can be repaired only at great cost, espe- cially if the structure be concealed within an embankment. Where room is an object, as in the streets of a city, the outer sides of the dike are conveniently held up by steep walls of stone, which add neither to the strength nor to the impermeability of the work. II. In geolo- gy, a wall of trap or other igneous rock, which traverses other rocks, and appears to have been produced by the flowing of melted matter into a deep rent or fissure. Dikes are distinguished from veins by the greater uniformity of their contents, by the parallelism of their sides, by their not ramifying into smaller veins, and by their usually larger dimensions. The name was given them from their frequently project- ing above the surface like a wall, owing to the degradation of the softer rock around them, dike being in the north of England and in Scot- land a provincial name for wall. They are from a few inches to more than a mile in thick- ness. In volcanic eruptions they are seen in process of formation, as deep rents open and are filled with liquid lava. In the English coal mines trap dikes are occasionally met with, forming walls across the line of the coal beds, cutting them off, and causing them at times to be thrown out of place. In the United States they occur likewise in the gold mines of North Carolina. In the Connecticut valley, in fissures of sandstone, as well as in New Jersey, the trap dike contains copper ore, indicating that the copper veins in these rocks have a com- mon origin with the dikes, and also with the barytes which forms the gangue or matrix of the vein. Prof. Dana remarks that the trias- sic formations along the Atlantic appear to be a repetition of the processes which occurred in the Huronian and Potsdam periods in the Lake Superior region. The trap rocks of Lake Superior are often remarkable for the grandeur of their basaltic walls and columns. DILKE. I. Charles Wentworth, an English journalist, born Dec. 8, 1789, died Aug. 10, 1864. He graduated at Cambridge, and early found employment in the navy pay office, where he remained 20 years. In 1830 he be- came editor and proprietor of the "Athe- nsoum," which speedily rose to a high rank in English periodical literature. In 1846, having intrusted the editorship of the "Athenaeum" to Mr. Thomas Kibble Hervey, Mr. Dilke under- took that of the "Daily News," from which he retired in 1849. A valuable collection of " Old English Plays," in 6 vols., was edited by him in 1814. II. Sir Charles Wentworth, son of the preceding, born in London, Feb. 18, 1810, died in St. Petersburg, May 10, 1869. He was educated at Westminster school and Cambridge, and from his interest in art was one of the earliest and most active promoters of the crystal palace exhibition of 1851. He declined the knighthood offered him for his services on this occasion, and also refused any pecuniary reward. He was a commissioner to the New York crystal palace exhibition in 1853, and one of the five royal commissioners of the second London exhibition in 1862, in which year he was created a baronet. He was active in the society of antiquaries and the royal geographical society. He sat in parlia- ment for Wallingford from July, 1865, to No- vember, 1868. HI. Sir Charles Wentworth, an English author and politician, son of the pre- ceding, born in Chelsea, Sept. 4, 1843. He was educated at Cambridge, where he grad- uated in 1866, and was called to the bar. He travelled in Canada and the United States, crossing to the Pacific coast, and sailing thence for Australia and the other British colonies in the South sea. The result of these travels he