but utterly failed to stem the rapid, and in fact could not hold her own in the current. Gauge No. 2 on June I read 40 feet above low-water. The last measurements were made From station 6+ 80 to station 14 inclusive, May 14, 1880. From station 19 +20 to station 21+ 20 inclusive, April 29, 1880. From station 25 to station 29 inclusive, April 12, 1880. From station 29+ 20 to station 31 inclusive, March 25, 1880. REPORT OF BOARD OF ENGINEERS. UNITED STATES ENGINEER OFFICE, San Francisco, Cal., August 19, 1879. GENERAL: The Board of Engineers for the Pacific coast has, in obedience to the telegraphic instructions of the Engineer Department, dated July 22, 1879, considered the points referring to the canal around the Cascades of the Columbia River, presented by Major Gillespie in his letter of August 6, a copy of which is appended, marked A. In this letter Major Gillespie recommends that operations at the locks be confined for the present to the excavation of the prism of the canal, leaving the masonry construction untouched, until the navigation of the river below the Cascades shall be improved, and that this improvement shall be at once undertaken by removing the reefs which lie in the river below the main rapids. The Board spent four or five days in the study of the maps, profiles, and ground, and in conference with Major Gillespie and his assistant, Lieutenant Powell, of the Corps, and in this way endeavored to reach a knowledge of the general situation and prospects of this important work. It will be remembered that in 1877 the Board considered the project for this work prepared by Maj. John M. Wilson, and recommended its adoption with certain modifications. Since the date of this report, which was in September, 1877, the river has reached points at low-water at the foot of the breakwater, 2 feet below the low-water assumed in the preparation of the original project. This low-water stage is said to be the lowest that the river has reached in 10 years. The department has also, since the date of the report of 1877, authorized an increase of width of chamber from 50 feet, as recommended by the Board, to 70 feet. During the last high-water stage Lieutenant Powell made observations upon the velocities of the current at different points below the lower end of the breakwater, as proposed by Major Wilson and as adopted by the Board, and found these velocities to be as high as 17.4 miles an hour. Gauges have also been established at different points along the line of the canal for a distance of 1.4 miles. These gauges have been read at different stages of the last high-water and have afforded the means of constructing a longitudinal profile of the river in its high stage, showing great variation in its slopes. The preceding statement is an outline of existing information bearing upon the subject of the canal at the Cascades, additional to that which was before the Board when it drew up its report in 1877, and in the light of these facts, we now proceed to consider the suggestions of Major Gillespie. The velocity observations already mentioned were made by Lieutenant Powell on the 16th, 17th, and 18th of June, 1879, when the river was slowly rising and still 12 feet below the high-water mark of 1876. Over a distance of 3,500 feet below the foot of the breakwater as now projected, the velocities necessarily to be encountered by a steamer endeavoring to reach the locks varied from 14.6 miles to 17.4 miles per hour. On August 4, 1879, when the Board saw the current, the river was 25 feet below the high-water mark of 1876, and was slowly falling. The velocity on this date was doubtless considerably less than it was at the date of Lieutenant Powell's observations. The Board is of the opinion, that reduced as the velocity was at the time of its visit, the current was yet too strong to be overcome by a steamer. The river has, at times since March 31, been considerably higher than it was on August 4, but never lower, so that it is reasonable to assume that during four months in the present year, beginning with April, the velocity of the current in this part of the river has not been lower than it was on August 4. In other words, navigation of the river was, for this period of time, impracticable. How much longer than four months, in the present year, the river has been and will be at this point, unnavigable, we cannot say with definiteness, but there can be no doubt that this period of compulsory disuse of the river may embrace half the year. In other terms, the locks under the present condition of affairs, although projected for high river, can be reached from below only at a low or medium stage. At a low stage of the river the current below the breakwater, although rapid, being in one place as much as 8 miles per hour, is practicable, and during this stage of water, which lasts about half the year, the break water can be reached from below and the locks used. In order, however, to make this low water navigation below the breakwater reasonable instead of barely practicable, it seems to us that the reefs which form the two main rapids below the breakwater ought to be removed. We are informed by the letter of Major Gillespie that no survey of these reefs has been made with the view of obtaining an estimate of the cost of their removal, but Major Gillespie estimates the quantity of rock to be removed approximately, from the information in his possession, to be 50,000 cubic yards, in order to give 10 feet at low stage of the river. The Board is of the opinion that such a survey and estimate ought to be made as soon as possible, to include the whole of the reefs, for the reason that there is some ground to hope that an extensive excavation of these reefs would not only improve the navigation of the river at the low stage, but also afford important relief in another and totally different respect, which we now proceed to notice. The gauges established by Lieutenant Powell, and read during the high stage of the present year indicate, as will be seen by the longitudinal profile accompanying this report, marked B, that there is an engorgement of the river in its high stage near station 54. By reference to the map prepared under direction of Maj. N. Michler, Corps of Engineers, October, 1874, a copy of which, it is supposed, is in the department, it will be seen that the first reef lies just below this station, and is probably the cause of the engorgement. If this reef be removed it must have the effect to lower the flood line along the breakwater and to lessen the height of this construction if it should be made to accommodate high-water navigation. The removal of these reefs will also have some effect in lowering the low-water level at the foot of the locks, and in this connection the Board thinks with Major Gillespie it is indispensable that the improvements of the river should precede the building of the locks. If the low-water at the foot of the locks be assumed on the data that we now have, and the locks be now built, it is quite possible and even probable that, when the reefs below are removed, and the low-water level at the foot of the canal lowered, the locks will fail to serve fully the purposes for which they have been projected. We summarize these opinions as follows: 1st. That the medium and high-water navigation of the portion of the river just below the canal is, under present conditions, impracticable. 2d. That the low-water navigation of this portion of the river is, under present conditions, practicable, but not convenient, and not such as ought to exist in the approaches to a canal of the magnitude and importance which this must always be as the outlet of an extensive agricultural country. 3d. That the low-water navigation can be improved and ought to be improved by the excavation of the reefs which contract the low-water section. 4th. That the excavation of these reefs will, according to the extent of their removal, tend to lower the level of low-water at the foot of the breakwater, and also to equalize the high-water slopes and velocities. 5th. That, inasmuch as the reference of the sills, the aggregate lift of the locks, and the height of the breakwater are dependent upon the regimen of the river, as it will be established by the removal of the reefs, it is a logical sequence that the construction of the masonry of the locks and of the artificial channel ought not to be commenced until the reefs are removed. The Board awaits the survey and estimates for the removal of these reefs and the results of the study of the cross-sections of the river at different points and at different stages before expressing an opinion as to the extent of excavation that ought to be undertaken. In the mean time, and during the time occupied by the removal of the reefs, the systematic observations of heights of water and velocities will be a valuable element in any further consideration of the subject. The Board sees its way with tolerable clearness through the processes which have been indicated to the successful accomplishment of lowwater navigation which may be expected to obtain for 6 months in the year. This result is not, however, without its difficulties and its serious contingencies, and one of the great advantages of the course proposed by Major Gillespie and approved by the Board is, that time will be gained for careful observation and study of what can be done and of what must not be attempted. Some of the points which we think require study and involve difficulty will be mentioned in what follows. Having reached the conclusion that actual construction ought to await the improvement of the navigation of the river proper, it seems hardly necessary, at the present time, for the Board to express an opinion as to the practicability or advisability of providing for high-water navigation. We are convinced, with the information before us, that high-water navigation will require the constructions spoken of as possibilities in our report of September 24, 1877, namely, that the breakwater will have to be extended to Bradford's Island, the channel behind the island excavated, and additional lockage provided at the foot. We believe that the cost of these works has never been carefully estimated, and we recommend that this be done at some time in the future, and before the high-water system shall be again considered. This high-water system involves one difficulty which is peculiar to itself, and another which it shares with the low-water navigation, both of which appear to the Board to be serious. We merely indicate them for the purpose of commending the study of them. The first is found in the following circumstances: About 2,000 feet below the lower end of the breakwater as now projected, the river, at its low stage, is only 400 feet in width. The base of the breakwater, added to the 70 or 80 feet of channel inside of it, will take up about one-third of the cross section of the river, where it is already too small. Whether or not it may be necessary to make some compensation for this contraction by cutting away the northern shore, and what may be expected to be the effect of the contraction in low or high stages, are questions of difficulty and importance. The second difficulty is due to the sliding of the hills on the southern shore. The effect of this on the proper position of the breakwater is direct. Indeed, this final position will result from a balancing and a compromise of evils. On one side there is a sliding mountain, which threatens at any moment to fill the canal, and which ought not really to be touched in excavation. On the other side is a river channel too narrow to be encroached upon. Yet the channel must be narrowed or the mountain cut. One or both of these courses must, of necessity, be followed. The circumstances of this work as they now appear, impress the Board with a sense of difficulty and expensiveness of construction, even for low-water navigation, and much more for a high-water system. Under existing circumstances, with the information before the Board, we are of the opinion that operations ought to be directed to securing, for the present, merely the low-water navigation, including the mediumstage navigation if this shall appear practicable during the excavation of the reefs. The additional information that will be obtained from observations of river phenomena during the interval, and a careful estimate of cost, will, in due time, justify an expression of opinion whether or no the high-water system is practicable or advisable. The Board has considered the proposition made by Lieutenant Powell in his letter of July 28, 1879, transmitted by Major Gillespie, and attached to his communication marked A. Having, however, reached the conclusion that the lock construction ought to be deferred until the low-water level at the foot of the locks, as affected by the improvement of the river below the breakwater is established, the Board does not think it necessary to express at present an opinion whether or not the plan of a single lift wall, as proposed by Lieutenant Powell, is preferable to a separation of the lifts. This question may properly be deferred until the aggregate lift is ascertained, and the epoch of resumption of lock construction approaches. The suggestion that the effect of cutting the hill upon the location of the breakwater be ascertained in advance has already been alluded to, and is approved. If at any time in the course of operations that we have recommended it shall appear to the engineer in charge practicable to make a test of Lieutenant Powell's proposition to supply water from the river at the head of the break water, to the channel inside of the breakwater, the Board would be glad to see it done. The trial will, we think, be inexpensive, and if the result proves unsatisfactory little will be lost, and something will be gained in increased channel room at the foot of the locks. It has, however, been suggested to the Board that possibly the removal of the reefs may so reduce and equalize the current at the foot of the main rapids and below that boats may be able to reach the locks in low-water without the shelter of the breakwater. This result would be very gratifying, and so long as there may be hope of attaining this object, it would not be judicious to undertake the construction of the breakwater, or to make a test of Lieutenant Powell's scheme. Respectfully submitted. C. SEAFORTH STEWART, Lieutenant-Colonel, Corps of Engineers. The CHIEF OF ENGINEERS, U. S. A. Major of Engineers. A. LETTER OF MAJOR G. L. GILLESPIE, CORPS OF ENGINEERS. UNITED STATES ENGINEER OFFICE, Portland, Oreg., August 6, 1879. COLONEL: I have the honor to present for the consideration of the Board the following recommendations relative to the construction of the canal around the Cascades of the Columbia River, Oregon. In order that commerce may reap at the earliest practicable moment the benefits arising from the improvement, I would recommend that the construction be limited for the present to the obtaining of low-water navigation around the Cascades. In the prosecution of this plan it is deemed preferable to improve first the river from the foot of the main rapids to the lower landing of the Oregon Steam Navigation Company, a distance of 6 miles, by removing the principal reefs, which dam the |