ij8 THE IMPROVEMENT OF RIVERS. 



same causes of failure, and as a result there is now no traffic on the river except that of 

 timber. The lock in question was 27 feet wide in the chamber, and of a length suffi- 

 cient to contain one barge. ' 



The widths of chamber used on rivers in this country are usually 27 feet, 36 feet, 

 and 52 or 55 feet, and on the Ohio, no feet. These widths are based on the size of a 

 standard coal barge, which at present is 25 to 26 feet wide, and 125 to 135 feet long. 

 A lock of the first size should not be built, unless under very special circumstances, 

 since it is too small to accommodate steamboat traffic, and if another size would be 

 too large for the river the project should be abandoned. It is much better wher- 

 ever practicable to build to the width 0/55 feet, with a good depth of water on the sills, 

 even if existing locks on the same river are smaller. It should be remembered that 

 the extra width merely involves some additional excavation, and a little extra expense 

 for miter walls and gates, while if the chamber is built too small, it must either be 

 enlarged later at serious expense, with delays to navigation, or it will not properly fulfill 

 the purposes for which it was designed. 



A few old locks have been enlarged in this country; but where new ones have 

 been built, even on streams having small locks, larger ones have frequently been put 

 in. In France many locks have been torn down and rebuilt with greater capacity. 



The practice of building the chambers with entrances narrower than the basin 

 has not obtained in America, although it is often to be met with in Europe. 

 Thus on certain of the new locks on the Moldau the entrances are 36 feet wide and the 

 basins 65$ feet wide. This saves material in the gates and cross-walls, and also avoids 

 much excavation of the approaches, but it delays the handling of the traffic, as the 

 boats, if in tows, have to be moved sideways in the chamber. 



Large locks, on the other hand, while they have advantages', have the inconve- 

 nience of wasting water and consuming time in filling and emptying the chamber where 

 only a small lockage is to be made. Generally this waste of water is of little conse- 

 quence, but there are times on some rivers where the supply of water is insufficient 

 and must be saved as far as practicable. An intermediate pair of gates is sometimes 

 introduced, and this not only obviates the objections named above, but has also the 

 additional advantage of allowing the continuous use of the lock during repairs to the 

 other gates. Another method, is to build a small lock adjoining the large one, of a 

 size to accommodate single boats and the smaller tows. The locks at Bougival, finished 

 in 1883, and at Suresnes, near Paris, are of this type. Where a fixed dam is to be con- 

 structed adjoining the lock, the smaller rivers are not usually sufficiently wide to 

 admit a double lock, but in wide streams and where movable dams are to be built this 

 plan has many advantages. 



Lift. In determining the lift of a lock and dam, that is, the vertical distance 

 to the crest of the proposed dam from the crest of the next one below, due regard 

 must be had to the riparian property and to any adjacent water-power mills or indus- 

 tries. The heights of bridges crossing the stream may sometimes have to be consid- 



