The cost of the new work has been estimated at £502,000 for the south jetty and £245,000 for the north jetty; making a total of £747,000, which includes £50,000 for a dredger to assist in hastening the scour. Already the new work, which has extended the old jetty about a mile (making it approximately 51⁄2 miles altogether), has had the effect of combining the several channels into one about 6,000 feet wide, and of increasing the depth to 25.5 feet. (See map of 1908, Fig. 6.) The results of the new work will be watched with interest as the construction progresses, and there seems to be little doubt that its completion will fulfil the requirements of the project.

Coos BAY (Figs. 7 and 8).

Coos Bay lies on the coast of Oregon, about 440 miles north of San Francisco. Its entrance from the ocean is between Coos Head on the south, and a long, low sand spit on the north. Southward for several miles to Cape Arago, several rocky ridges extend from the shore into the ocean in a northwesterly direction, and act as "cut-off" spurs tending to reduce the effect of storms, to interfere with littoral currents and to oppose the free sand flow. The conditions ordinarily found at the ports along this coast are thus modified in this locality in an important degree.

The north spit is approximately 6 miles long and about 1 mile in average width between the bay and the ocean, the sandy beach of which this is the free end extending northward for over 20 miles. All the currents are tidal, the mean range of the tide being 4.8 feet, although maximum ranges of 10 feet have been observed; the average mean discharge is estimated at 133,000 cubic feet per second. The discharge on the average neap tide is 96,000 cubie feet per second, while that on the maximum tides is probably over 310,000 cubic feet per second. Surface velocities of 41⁄2 miles per hour on low ebb tides have been observed at the entrance.

The entrance to this bay is obstructed by the usual encircling bar, which, in its original condition, ordinarily carried depths of about 9 feet, although occasionally better depths would prevail. It is difficult to follow the action of the sand drift at this port, but it seems probable that its direction is northward and that the building out of the north spit is caused by eddy currents. The deep-water channel apparently underwent the usual cyclic changes in the course of years, passing from the extreme north to a direction westward from Coos Head. As the southern spit prolonged itself northward the northern spit built out southward, causing an overlapping which made it necessary for vessels to pass broadside on to the sea for long distances before entering the Lay.

The original plan of improvement contemplated the construction of two jetties, one to extend westward from Coos Head and the other from the north spit, converging toward the bar, where they were to terminate at a distance apart of 1,500 feet. The length of the north jetty was to be 9,600 feet and of the south jetty 4,200 feet. The purpose of these jetties was to control the sand movement and direct the currents to a selected place on the bar, so that a depth of at least 20 feet, at lower low water would be produced and maintained. The location of the channel selected corresponded with that of the "breakout, " where the best depths were observed. The total cost was estimated at £498,000.

Construction was commenced in 1891, and the projected depth was obtained in 1894 upon the completion of the north jetty, which was undertaken first. This was apparently not the windward jetty, but in view of the local conditions it was decided to construct it first, in the belief that the moving sand would be more effectively impounded than if the south jetty were built first. The assistance of Cape Arago and the neighboring dikes was relied upon to control to some degree the northward movement of the shifting sand.

The results of the construction of this jetty have been so favorable that the proposed south jetty has never been built, the intention being to postpone this work until its necessity becomes more apparent. Since 1894, when the projected depths were first obtained, favorable conditions have continued to the present time. The cost of the jetty has been £144,000. Considerable difficulty was met with in maintaining the outer end at full height; but the quantities of rock now placed there have been sufficient, even after subsidence, to direct the currents across the bar, thus maintaining the depths required by the project.

This bay may clearly be regarded as an instance of the successful application of the jetty system, the bar depths having been more than double and successfully maintained for upwards of fifteen years at far less cost than was expected.

YAQUINA BAY (Figs. 9 and 10).

Yaquina Bay, on the coast of Oregon, has total area of about 5 square miles. It is the mouth of the Yaquina River, and is a long, narrow estuary having a number of tidal sloughs in addition to the main channel. The fresh water flow into this bay is insignificant except during freshet stages, at which times the addition to the tidal flow acts materially to assist the ebb currents in their scouring action on the bar. These freshets, however, are so infrequent and so irregular in their discharge as to make it undesirable to rely upon them for definite results.

The entrance lies between a rocky headland on the north and a sand spit on the south, and was originally blocked by the usual crescent-shaped bar, over which the depth was seldom more than 7 feet at the mean of the lower low waters. The mean range of the tide is 7 feet, and the extreme range at spring tides about 11 feet. There is a mean tidal discharge of about 32,000 cubic feet per second, and a maximum discharge at spring tides of about 100,000 cubic feet per second.

Before improvement the channel over the bar was variable. The sand drift is northward, and although not observed here with the same clearness as elsewhere, the usual cycle of change has been operative. The entrance is protected by a rocky reef running nearly north and south and lying about a mile off shore, over which the depths are from one to several fathoms. This reef has played an important part in protecting the works constructed for the improvement of the bay and is unquestionably a part of the rocky headland.

The original project for the improvement of this harbor in 1881 provided for the construction of two jetties extending westward from the entrance, one commencing on the high ground on the north side, the other extending out from the sand spit on the south; and converging to a distance apart of about 1,000 feet at their outer ends. A depth of 10 feet over the bar at the mean of the lower low waters was contemplated, or 17 feet at ordinary high tide.

The work was completed in 1895 at a total cost of £138,000; the south jetty being built to a length of 3,500 feet and the north jetty to a length of 2,800 feet. A new channel was obtained through the bar, having depths of 13 feet to 15 feet at mean lower low water and 21 feet to 22 feet at high tide. These depths are considerably in excess of what were expected, and have been maintained for many years at slight expense.

GRAY'S HARBOR (Figs. 11, 12, and 13).

Grays Harbor is a large bay in the western part of the State of Washington. It extends about 17 miles from east to west, with a greatest width from north to south of 14 miles. The greater portion of the bay consists of tide-flats bare at low water and separated by channels having ample depths and areas for anchorage and such purposes of navigation as the commerce of the bay requires. These flats are covered when the tide reaches an elevation of about 5 feet above the mean of the lower low waters. The area of the bay at high tide is about 96 square miles, whereas the low-water area is about 30 square miles, or less than one-third of the high-tide surface. Several streams enter the bay, but the amount of fresh water is small. The extreme range of the tide is over 16 feet, the mean being 8.4 feet. The tidal prism at an average tide gives a mean outflow of 748,000 cubic feet per second, and a maximum tide has a mean discharge of over 1,000,000 cubic feet per second.

The entrance to this bay from the Pacific Ocean lies between two long low sand spits, Point Brown on the north and Point Hanson on the south, the distance between being about 12,000 feet. The entrance is encircled by the usual crescent-shaped bar, and the cyclic changes common to these harbors have been operative here.

The direction of the channel swing and the extension of the south spit northward plainly indicate that the shifting channels over the bar are produced by pressure from the southward. Accordingly, the original project provided for the construction of a high-tide jetty extending out from Point Hanson westward, to impound the moving sand and protect the channel from encroachment. It was hoped that the action of this jetty in cutting off the waste flow to the southward would be ample of itself to maintain 24 feet over the bar at the mean of the lower low waters. It was commenced in 1896 and completed in 1902, though never built to its full projected length. The estimated cost was £200,000, and the actual expenditure has been slightly in excess of that sum.

The contraction secured by the construction of this jetty not having been - sufficient to produce the depths desired, a north jetty has been recently undertaken about 9,000 feet long, at an estimated cost of £120,000, to cut off the currents which waste their energy to the northward around Point Brown. The outer ends of the two jetties are to be about 6,000 feet apart. This work is now in progress.

HUMBOLDT BAY (Figs. 14, 15, and 16).

Humboldt Bay lies on the coast of California, about 200 miles north of San Francisco. It is an estuary about 14 miles in length and from 1 mile to 4 miles in width, and is separated from the ocean by two long narrow sand spits from 4 mile to 1 mile in width, one lying to the north and the other

to the south of the entrance.

The beaches and sea bottom are composed of a fine, mobile sand, which has caused great variations in channel location and depth. On the ocean side of these sand pits the beach slopes seaward with a rapid inclination, averaging from 60 feet to 65 feet per mile. This condition is favorable for improvement, but increases the exposure to storms, which in this vicinity are of great violence.

The bay embraces about 24 square miles at high tide, and at low tide its area is 13 square miles. The mean rise of the tide is 4.4 feet. The average discharge through the entrance is estimated at about 105,000 cubic feet per second, and the maximum rate of flow is estimated to be over 200,000 cubic feet per second on the average tide. This discharge is practically all tidal, as there is no fresh-water stream of any size entering this bay. The crescentshaped bar, sifting entrance, cyclic changes and other usual conditions were all in existence here.

The original plan of improvement contemplated the construction of a single south jetty, which it was expected would fix the channel in position and produce and maintain a depth of at least 20 feet at low water datum. Work on the south jetty was commenced in 1884, with the result that the width of the entrance was increased by scour beyond safe limits. Accordingly in 1890 the project was modified to provide for shore protection and for a north jetty extending out from the north spit and verging toward the south jetty to a point 2,100 feet distant therefrom. As this work proceeded the channel deepened, until in 1899, when the jetties were completed, there existed a depth of 28 feet at the mean of the lower low waters, or more than double the ruling depth before work was commenced; and in 1903 a survey showed a minimum depth of 31 feet.

The length of the south jetty, as constructed, is 8,000 feet, and of the north jetty 7,400 feet. They are rock mounds built on brush mattresses 4 feet thick; the total volume of rock being about 1,148,000 cubic yards, and of brush about 88,000 cubic yards. The mean of many observations shows that on the sea side the rock stands at an average slope of 1 vertical to 2.65 horizontal, whereas on the harbor side the slope is 1 on 2.25. The total cost of the work was £412,000.

Owing, however, to the subsidence of the outer ends of the jetties, and possibly also because they were not extended as far as they should have been in the beginning, shoaling has since taken place; the south jetty having been overlapped by the sand wave. In 1907 the depth in the channel at mean lower low water had fallen to about 22 feet.

It seems plain, upon careful examination, that the new shoaling has not been caused by pushing the old bar seaward, a result that has been feared by many engineers, but rather has arisen from the lack of sufficient storage space in the groin of the south jetty to impound the moving sand. Until this space was filled the favorable effect of the ebb tides was continuous and cumulative; but as soon as the jetty could no longer hold back the sand flow from passing around the end, the bar depths began to deteriorate and the channel to swing northward across the line of the north jetty.

It is probable that an extension of these jetties will be necessary to regain the favorable depths previously obtained. This work is now under consideration by the Government engineers.

The paper is accompanied by twenty-one maps, from which the figures forming Plate I have been selected.

Andrew Atkinson Humphreys

Andrew Atkinson Humphreys (see frontispiece) was born in Philadelphia, November 2, 1810. He entered the United States Military Academy July 1, 1827, and was graduated and commissioned a brevet second lieutenant of artillery July 1, 1831. He served in the artillery at Fort Moultrie, S. C., the Military Academy, in the Cherokee Nation, and at other points until September 30, 1836, when he resigned from the service.

Most of his work in the Army had been in connection with surveying, and upon his resignation he became a civil assistant to Major Bache on the plans for the Brandywine Shoal lighthouse and Crow Shoal breakwater in Delaware Bay. On July 7, 1838, he was reappointed into the Army with the rank of first lieutenant in the Corps of Topographical Engineers, and his first work was on the improvement of Chicago Harbor in 1839, and also on a survey of Oswego Harbor defenses and Whitehall Harbor, N. Y.. in the same year. He was an assistant in the Topographical Bureau at Washington, D. C., from 1840 to 1841, and served in the Florida War in 1842. From 1842 till 1844 he was in the Topographical Bureau at Washington, D. C. From 1844 to 1849 he was in charge of survey work in the field. He was promoted to captain, May 31, 1848. In 1849 and 1850 he was engaged on a topographic and hydrographic survey of the delta of the Mississippi River, and from 1850 to 1851 continued in general charge of the work and in the preparation of the now famous "Humphreys and Abbot's Survey of the Mississippi." The work that he done in connection with this survey and the data obtained is yet standard, and the book itself is a classic in hydraulic literature.

The years 1853 and 1854 he spent in Europe examining means for the protection of delta rivers against inundation, but on his return to this country in 1854 was placed in general charge of the exploration and surveys for railroad routes from the Mississippi River to the Pacific Ocean, and of the geographical explorations west of the Mississippi. In addition to this duty, from 1856 to April 5, 1862, he was a member of the Lighthouse Board, and in