construction on the rivers of this country: In one class the beams are Mr. Thomas. placed horizontally, and transmit the strains to the walls and the opposite leaf through heel and toe posts; in the other class the supporting beams are placed vertically, connecting with horizontal girders at bottom and top. This class of gate has less metal than the other when the length is considerably greater than the height, but a heavy strain is transmitted through the top girder to the wall w ell toward its top. In the writer's opinion it is not to be preferred to the horizontal framed gate. A more serious objection to it is that when rust has weakened the uprights at the water line, as it probably will, the entire gate must be renewed. With horizontal framed gates it would only be necessary to renew the lower portion. The use of a buckle-plate skin will permit of a wider spacing of girders and effect a material saving of metal, because these plates are much stronger than flat plates of equal weight, and will require no stiffeners, even in very wide panels.

Originally, metal gates had a double skin in order to secure buoyancy and consequent reduction of weight, but it was found that the compartments leaked and were not kept pumped out, so that the additional plating was simply so much weight to be carried without any beneficial result. It has also been found that the upper compartments fill with mud and induce rust. Without doubt the single-skin gate is to be preferred in every way. One objection to all metal gates is that they are likely to rust at the water line and below, when they cannot be kept clean and painted, and the writer has considered the advisability of building the upper portion of metal and the lower of wood. The latter could be renewed at any time without disturbing the former, and with very little delay to navigation. Wooden gates are short lived. The writer knows of few gates which have lasted more than sixteen years; many are partially renewed within ten years, and a few in less. There is only one lock provided with iron gates on the tributaries of the Upper Ohio, but these seem to be perfectly good after twenty-one years' service. In his work on mitering lock gates, Major Hodges gives the average life of a metal gate at forty years, when properly cared for and repaired.

The method of operating the gates adopted by the author seems to be undesirable, although experience may prove otherwise. Mechanism somewhat similar, but, doubtless, imperfect in construction, was tried a number of years ago on a lock on the Kentucky River, and, later, was supplanted by something else. The writer was told that it was not satisfactory, but has no information on the subject. The most common method of gate operation is by a rack-bar and pinion turned by capstan bars, but it is not wholly satisfactory, partially because of the friction of the rack and pinion and partially because the bar, in order to reduce its length, is attached to the gate too far from the toe. The prim

Mr. Thomas. itive wooden spar and modern wire rope winding on a capstan, as seen on the Kanawha and elsewhere, is the simplest and most satisfactory device the writer has yet observed for hand operation. The spar and line are attached at the toe, the length of spar not being objectionable when it is an ordinary pole, and the best point from which to operate is thus secured. It is worthy of note that the new locks on the Moldau, in Bohemia, are provided with rack-bars operating under the coping, where they are out of the way during maneuvers. The same system has an example on the Fox River in this country.

The cost of wooden gates, for locks from 50 to 55 ft. wide, with about 12-ft. lift, ranges from $1 500 to $2 500 per leaf, usually being about $2 000. Steel gates will not usually cost any more, if designed with a view to economy. In adopting the balanced valve the author followed the practice which has the advantage of long and fairly satisfactory trial, and, with the modifications and arrangements which he has provided, most excellent results should follow. This valve is sometimes used with a vertical and sometimes with a horizontal axle, and seems to work equally well in either way. Other forms of valves in use are the gridiron sliding valve, in which the valve is pierced with rectangular openings, and the cylindrical valve, which consists of a cylinder, from 4 to 6 ft. in diameter and 18 to 20 ins. high, sliding vertically inside a chamber having a water-tight cover. This cylinder or ring encircles the culvert opening, and, when down, shuts off the water. When raised, which is an easy operation, as the water is pressing equally from all sides, the water goes into the culvert under the cylinder. This valve is in satisfactory use on the Muskingum River, and is being adopted for new locks on the Big Sandy and Kentucky. The writer has been considering the advisability of dispensing with the chamber over the cylinder, dropping its cover down to the top of the cylinder, and sliding the latter up on guides on the outside. This cylindrical valve has been rendered self-operating by the introduction of water through its cover, and a patent has been issued to Major W. L. Marshall, and another to Mr. Sanford L. Cluett, for devices of this character. Some of the latter have been made for trial on the Big Sandy, but are not yet in use.

General Remarks.—In preparing plans for work of the character of that under discussion it should always be remembered that repairs will be costly, tedious and detrimental to navigation, because the water will be troublesome, and it will be necessary to close the locks for a time. It is of the first importance, then, not only to make the various parts as simple as possible, but also to make them stronger than necessary. Especial attention should be given to designing all valves or other movable parts so that they can be readily removed for examination or repair. It is only necessary to go over one of the older improvements to be convinced of the necessity for such cautions. The

exposed ends of anchor bolts will rust eventually, so that renewal Mr. Thomas. will be necessary, and it will be well to provide sleeve nuts in the original construction so as not to necessitate digging the old bolts out of the masonry.

Of late years, considerable taste has been displayed in the design of lock buildings and in the care of the grounds. These places should be veritable parks, with grass, shade, flowers, and neat walks and fences; in fact, they should be object lessons to their several communities. A very little money will go a long way when all the labor is ready at hand and under pay the year round. The works themselves should be kept in the best of repair, and lock gates, irons, machinery, boats, and such property as can be improved thereby, should be thoroughly overhauled and painted every year. It is a lesson, to those engaged upon the works, which is very cheap at the price, as it causes each man to be more careful, to take more pride in his work and in himself, and thus he becomes a valuable citizen as well as a valuable employee.

D. M. ANDREWS, M. Am. Soc. C. E. (by letter).-This paper is a Mr. Andrews. valuable contribution on a subject of which there is far too little information available. There is little to criticize in the paper; the writer, however, wishes to discuss certain of the points from the viewpoint of his own experience.

The Black Warrior and Warrior are one and the same river; the name Black Warrior changing to Warrior at Tuscaloosa, as explained by the author. The Black Warrior has stable banks and bottom. The Warrior has caving banks and a shifting bottom.

The adoption of the fixed type of dam for the Black Warrior was unquestionably the best; and, for the reasons given by Mr. McCalla, particularly the small low-water discharge, the fixed type was the only type that could have been safely adopted for the Warrior. With the fixed type, however, the pools between the dams will in time fill up, and constant dredging will be required to maintain a channel of the proposed width and depth between the locks. With dams of the movable type this filling of the pools could be prevented by lowering the dams during periods of high water, and letting the river clear itself of accumulations of silt and gravel.

The writer believes that the advantages or disadvantages of locations at convex or concave shores are, except in abnormal situations, more apparent than real; however, other things being equal, a straight reach is probably the best location. The writer's experience leads him to the following conclusions:

There should be guide piers, both above and below every lock, placed an angle of about 100 with the axis of the lock. Where there is much disturbance below the dam during periods of high water, the lower pier should extend from the lower end of the river wall. Solid

Mr. Andrews. piers not less than 150 ft. in length, and longer where the volume of traffic is considerable, with drift passages at the lock wall, are preferable to pile clusters.

Rack bars for maneuvering lock gates are objectionable in rivers carrying much drift, for they have to be removed when the lock is about to be submerged, and replaced when it emerges. The maneuvering apparatus described by the author is not open to this objection, and, as the writer knows from experience, is in other respects a most admirable arrangement.

The design of the dams at Locks Nos. 1, 2 and 3, Black Warrior River, is bad, on account of the stepped lower slope. Drift passing over the dams would cause the displacement of the slope stones, and entail constant expense for repairs. A better arrangement is that in which the stones are set with the beds normal to the slope, as at Lock No. 4 of the same river. Dams of this type, viz., crib-filled dams with a lower slope of stone should have the lower slope laid without cement beds or joints, thereby allowing the free passage of leakage. The face, whether of masonry or sheet-piles, should be made watertight, or as nearly so as possible; but in rivers of considerable lowwater discharge, it is not the part of economy to go to any great expense to secure a water-tight face. As usually designed, it is only necessary to maintain the surface of the pool at the crest of such dams. The low-water discharge not needed for that purpose may pass the dam as leakage. This last statement does not apply, of course, to dams intended to develop power.

The writer has recently repaired and raised to a height of 15 ft. (the height being originally 12 ft.), a crib-filled dam, 700 ft. long, built on a foundation of gravel, mud and rotten limestone. The repairs and addition to the height were made by building a heavy stone slope from below and over the crib, or what was left of it. The stones in the slope contained from 1 to 3 cu. yds. each, and were laid dry with the beds normal and the faces flush with the slope. The face of the dam was of double-lap, 4 x 12-in. and 2 x 12-in. sheet-piling. The sheetpiling extended 5 ft. above the crest, as a protection bulkhead to the workmen below. After the slope below was finished, the piling was cut flush with the crest. The operation was repeated until the dam was finished. Quarry waste was filled in against the sheet-piling from above. No attempt was made to get a water-tight face, the low-water flow being sufficient to maintain the upper pool at the crest, with the leakage allowed. An apron at the toe, to prevent scour, was built of large stones roughly placed, and the interstices were filled with smaller stones. The work was done by hired labor, and cost, every expense included, $2.51 + per cubic yard.

As to the expediency of the improvement of our rivers, opinion is as diverse as it once was concerning the proper gauge for our railroads,

and it seems that the arguments for and against are likely to be as Mr. Andrews. vigorously presented as were those fought over in the days of the "Battle of the Gauges."

The writer can do no more than generalize, not having statistics at hand, but he ventures the assertion that, should the Erie and Welland Canals be abandoned, freight rates from the West to New York would go soaring, and New Orleans would become the chief shipping point for the export trade of the country. He is aware that pages upon pages of statistics have been printed showing that the railroads entering New York from the West can and do carry freight as cheaply as the same is transported through the canals; but those statistics being presentations of facts make no prediction of the probable effect of an abandonment of the water lines of transportation from the Great Lakes to the Eastern Coast.

The writer recently had some machinery shipped to a point on the Lower Mississippi River, a part coming from Bridgeport, Conn., and a part from Birmingham, Ala. The freight rate from Bridgeport was practically the same as that from Birmingham, because Bridgeport, though the length of haul was against her, had the advantage of continuous water transportation.

Statistics of this kind interest the people at large, and, as long as conditions remain as they are, there will be a demand for the improvement of our rivers, though argument be piled upon argument showing that railroads can be built, operated and maintained, at far less cost than the cost of improving, and maintaining the improvement of, our rivers.

R. C. MCCALLA, M. Am. Soc. C. E. (by letter).-The writer feels Mr. McCalla gratified that his paper has brought out an able and interesting discussion of a subject on which the literature is rather scanty, considering the number of important works of this character in the United States and other countries. He hopes to profit by many of the ideas and arguments advanced.

There are

Location.-The Warrior is a narrow, crooked stream. very few straight reaches and few or no places wide enough to take in the lock and abutment and a dam long enough to provide sufficient spillway for the proper discharge of flood waters. The width of the stream at low water varies from 100 to 300 ft. and averages about 200 ft., therefore the locks and abutments must be set well back into the banks. If straight reaches were available for locations, curved approaches leading back into the stream would be required at both ends of the lock. If locations were made in bends and on the concave shore, still sharper or longer curves would be required in the approaches to get back into the stream.

Wherever a lock is located, it forms a barrier to the current, and thereby causes silt deposits in the lock and approaches; also, during