Page:1902 Encyclopædia Britannica - Volume 27 - CHI-ELD.pdf/574

 DRi-VA —DREDGING

528

and is, besides, typical of a class of draughts problems which may be described as analytical, in contradistinction to “strokes.5 Problem No. 1, by Wm. Payne. BLACK.

WHITE. White to move and win.

Solution :■ 272823-18 32-28 3-«-24-28 1-24-20 a. 12-16 same as Var.

Tirol under the mountain of Rohrwald, at a height of 1670 metres, whence, after passing across Carinthia and Styria, it penetrates into Hungary, where it forms the frontier-line between the mother country and CroatiaSlavonia. From Villach it is navigable by rafts, but by steamers only from Bares downwards, to a distance of 155 kilometres. Of its confluents only the Mura is considerable, but it receives the excess of many alpestrine ponds. The Drava flows into the Danube close under the town of Eszek; at this spot it has already a breadth of 325 metres, and a depth of 6'5 metres. Because of its tortuousness from Bares downwards it is defended by strong dams; its length is 501 kilometres, with a waterregion of 47,191 square kilometres. In the escutcheon of the Kingdom of Hungary the Drava is represented, with the Danube, the Tisza, and the Szava, as one of the largest rivers of the country.

28-32 19-24 1511 32 18-15Dredging.—The use of dredging plant and11-15 the 27-31 White 2-28-24 12-16 24 19-24 selection of special appliances to be used in different 15-19 wins. 28-32 32-28 localities and under varying circumstances requires24-27 the 31-26 1619 exercise of sound judgment on the part of the engineer. I. at 5th move. In rivers and estuaries where the bottom is composed of Var. I. light soils, and where the scour of the tide can be so guided, 8-12 15-11 19-16 28-32 24-27 18-15 by training walls or other works constructed at reasonable 23-18 White 18-23 8-12 15-18 i 16-20 12- 8 wins. 16-11 32-27 expense, as to keep the channel clear without dredging, it 12-16 15-18 18-15 23-19 12- 8 28-32 24-19 is manifest that dredging machinery, with its great cost for 8-12 11- 8 27-23 27-24 32-28 annual upkeep, should be as far as possible avoided. On 5. 24-28 same as Var. II. at 1st move. Var. II. 12-16, 15-11, 16-19, 32-27, 28-32, 27-31, 32-28, the other hand, where the bottom consists of clay, rock, or other hard material, dredging must, in the first instance 11-16, 19-23, 16-19. White wins. Var, Var. III. 24-19, 32-28, c 19-16, 28-24, 16-11, 24-20, 11-8, at any rate, be employed to deepen or widen the channel. 18-15. White wins. In other instances, as in the Mississippi, a deep channel c. 12-16, 28-32, 19-24 or 16-20, same as Var. II. at 5th or 9th has for twenty years been maintained by jetties, with moves respectively. White wins. occasional resort to dredging to preserve the required Problem No. 2. channel section and to hasten its enlargement. The bar BLACK. of the Mersey is 11 miles from the land, and the cost of training works would be so great as to render them impracticable ; but by a capital expenditure of £120,000, and an annual expense of £20,000 for three years, the depth of water over the bar at low water has been increased by dredging from 11 ft. to 27 ft., the channel being 1500 ft. wide. The effects of dredging operations upon the trade and prosperity of a port are nowhere more forcibly shown than in the case of Glasgow. In 1755 only small vessels with a draught of 3 ft. or less could reach Glasgow at high water of spring tides. Now vessels drawing 27 ft. come WHITE. up on an ordinary tide. Formerly some of the river streets White to move and win. of Glasgow were often flooded; now, consequent upon the The above position is a fine example of another class of problems, straightening, deepening, and widening of the river, flooding namely, “strokes.” It is formed from the “Paisley” opening, never occurs. In 1755 the rise of tide was only about 2 thus :— ft. 5 in. The extreme range of tide in Glasgow harbour 9-13 15-10 11-16 26-19 11-16 22-17 is now 22 ft. These remarkable results have been due 25-22' re 2- 7 24-19 9-13 25-21 4- 8 to the dredging carried on in the river Clyde. Between 8-11 17-14 6- 9 29-25 7-11 28-24 10-17 23-18 13-17 19-15 1844 and 1897 the quantity of material dredged from the 12-16 16-20 21-14 16-23 31-26 river and deposited outside its mouth was 50,721,710 cubic re. This forms the position on the diagram. The solution is as yards. The tonnage of goods imported and exported has follows:— risen from 1,023,216 tons in 1851 to 5,673,152 tons in 27-23 7-14 18- 9 14-23 26- 3 1897. Similar results have been obtained in the rivers 20-27 9- 6 5-14 21- 7 27-31 Tyne and Tees. In the Tyne dredging amounting to 14- 9 1-10 23-18 3-10 3- 7 White wins. Jacques and Campbell. 96,362,136 tons was done between 1860 and 1896, at a Recent Boohs on Draughts.—The most important recent works on cost of £1,766,639; the average rate was 4'4 pence per the game are Lees’s Guide to the Game of5 Draughts, Hill’s Manual ton, which, however, does not include interest upon the first (for beginners), Kear’s reprint of Sturges and Drummond’s works cost of the dredging plant. The registered tonnage of on the game, and Gould’s Problem Book. The Encyclopaedia of ships clearing the port has risen from 3,120,265 tons in Draughts bids fair to be a most useful compilation of the best published play on each opening. The principal magazines de- 1860 to 6,752,252 tons in 1896. At Rotterdam, Antwerp, voted to the game are the Draughts World, the North American Calais, Dunkirk, and Ostend equally satisfactory results Checker Board, both monthly publications, and the Draughts have followed the dredging operations undertaken, and Players' Quarterly Review. (j. m. M. D. ; R. J.) similar results have been obtained by the dredging works Drava or Drave, one of the right-bank affluents at the Sulina mouth of the Danube. It will be seen, thereof the Danube, 668 kilometres long. Its sources are in fore, that dredging operations form a most important de-