At a cost of about $15 per day a grading crew with this jet will move from 500 to 1,800 cubic yards of earth in a day, the amount depending upon the character of the bank and the slope to which it is graded.

It is believed that there should be added to each hydraulic grading boat a hydraulic dredge operated by a centrifugal pump to enable the grading of the bank to be carried on below the water's edge. One of the weakest points in the revetment system is the irregular position of the subaqueous mattress due to irregularity of the bottom.

Mattress weaving and anchoring.-The mattress, 70 to 90 feet wide and 12 inches thick, is woven continuously downstream on a barge fitted up for the purpose, lying normal to the bank, the inner edge of the mattress extending about 4 feet from the water's edge up the sloped bank.

A specially designed boat, 25 by 70 feet, is used in mattress weaving. The lower gunwale of this boat is high, the upper one low, and raked to offer less resistance to the current. From the upper gunwale a calked platform, 134 by 66 feet, rises on a slope of 1 on 3, giving a working surface for the weaving. On this sloping platform are placed launching ways of 3 by 8 inch stuff, spaced from 6 to 10 feet apart. At either end of the platform outriggers are built for carrying the mattress beyond the width of the boat. At the rear end of the launching ways and on a level with their tops a brush platform, 12 by 66 feet, extends lengthwise the boat. Its lower edge is flush with the lower gunwale of the boat and it is supported 8 feet inboard by stanchions. The boat is stiffened longitudinally by a truss.

On the sloping ways of this boat the mattress is woven. When the mattress has been woven to the top of the ways, the barge is pulled downstream from under the mattress until the edge of the completed mattress rests on the lower portion of the ways; weaving is then resumed where it was left off and carried on until the top of the ways is reached again. A continuous mattress is thus secured.

Straight, freshly cut willows, not less than 12 feet in length and from three-fourths to 24 inches in diameter at the butt ends, are used in the mattress. One cord of willow brush will make about 140 square feet of mattress 1 foot thick. These willows grow on the sand bars formed by the river and are the best material for the mattress, being very pliable.

For starting the mattress a continuous bundle of willow brush 12 to 14 inches in diameter is made of a length equal to the width of the mattress and well wrapped with wire strand. Into this bundle the butts of the willows are forced at an angle of about 35 with the axis of the mattress. The mattress is woven very much as straw is plaited for various purposes, three to five willows being used in carrying the stitch. The ends of the willows projecting over the inner and outer edges of the mattress are turned in and well woven into the mattress, forming strong selvage edges. The brush for weaving is brought in wire bundles and laid crosswise, butts upstream, on the platform of the mattress boat. The bundles are then opened and the brush is passed one or more pieces at a time to the weavers.

To give additional strength to the mattress, and for the purpose of anchoring it to the bank, a system of galvanized-wire strands, running lengthwise and crosswise of the mattress, is used. Both longitudinal and transverse members are composed of two -inch strands each, made of No. 11 wires. One of these strands lies wholly underneath and the other wholly on top of the mattress. Both longitudinal and transverse

wires are spaced 10 feet apart. All the longitudinal members are paid out under tension, as the mattress is made, from reels on the mattress boat, the top strand of each longitudinal passing through a fair leader suspended some 18 feet above the brush platform.

There are also transverse members of two -inch strands each, extending one strand on top of the mattress and the other directly underneath it, from the outer selvage edge to deadmen on top of the bank back of the graded slope. They are laid out about normal to the axis of the mattress at a distance apart of 10 feet measured along this line. The transversals are run out from a reel on shore, the bottom part first, enough strand being pulled through past the outer selvage of the mattress to reach ashore when laid back on top of the mattress. Both parts of the transversals are laid just after the weavers pass the line, so that they are not woven into the body of the mattress. At all points of intersection of transversals with longitudinals the four parts of strand are brought together and fastened by stirrup bolts or clips of-inch iron, but before the fastenings are made tight both parts of the transversals are put under tension from the outer-edge selvage edge to deadmen ashore by means of blocks and tackle. The deadmen are either rough blocks of stone, containing 2 to 3 cubic feet, or pile butts 12 inches or more in diameter and 4 feet long. The deadmen or anchors are planted 8 feet back of the top of the graded slope and from 3 to 5 feet deep, according to the character of the ground. From the top of the slope to the deadmen in place the strands lie in a narrow trench dug for that purpose.

The average day's work of a weaving crew is about 100 linear feet, costing from 60 to 70 cents per linear foot.

Sinking and ballasting mattress.-Specifications for standard revetment provide that three-fourths of a cubic yard of riprap stone per linear foot of mattress shall be used in sinking it to close contact with the bottom, the distribution being such that the weight per square foot of mattress increases from the shore out. It is also specified that an additional 50 cubic yards of stone shall be placed on 50 linear feet of mattress at the head and 1 cubic yard per linear foot on all laps. The stone is thrown from a barge, which is dropped downstream over the mattress with its outer end somewhat in advance of the shore end. It seldom happens that the full complement of stone is placed in sinking, as a sudden shifting of the barge is often necessary to prevent buckling of the mattress, especially in a swift current. It is therefore usual to go over it a second time. The sinking is not carried closer than 150 to 200 feet above the mattress boat, and as much as 1,000 linear feet, or even more, mattress is sometimes made before sinking is commenced. There is danger, however, in having so much mattress afloat, as a sudden rise may occur, and, though it might not otherwise damage the work, would possibly so foul the mattress with driftwood as to seriously impair its efficiency.

The operation of spawling the inshore edge of mattress precedes the paving of the bank, and consists of filling well the interstices of the mattress from its inshore edge to the contour 3 feet below standard low water with small spawls or quarry chips and fairing up with the same material the shoulder formed by the edge of the mattress where it lies on the graded slope. This spawling serves to stop wave action through the mattress and to solidify it against ice in the event of loss of the paving or ballast. About one-tenth of a cubic yard of spawls per linear foot is required.

Paving and spawling upper bank. The upper bank from the contour 2 feet above standard high water to standard low water, and as much lower as the existing stage of river permits, is covered with a paving of riprap stone 12 inches thick at standard low water and 12 inches, 8 inches, and 6 inches thick, respectively, at the top of 1 on 2, 1 on 21, and 1 on 3 slopes. A covering 2 inches thick of spawls or fine quarry chips is put on the paving, thus completing the revetment. The paving is done from the top of the slope down, the stones being set up edgewise and placed with some care to make a compact covering, so that when completed ready for the spawls it presents an appearance of a reverse shingling. In this form it is well adapted to resist wave action and dislodgment by ice, driftwood, or other forces to which it is likely to be exposed. The spawls, thrown on at and near the top of the slope, are raked down over the pavement, filling the interstitial voids and finding lodgment in the paving surface.

As will be seen from the above, the quantity of riprap stone for paving, as well as the spawls required per linear foot of bank, will vary with the height between the standard high and low water planes, the height of bank when lower than 2 feet above standard high water, the stage at which the work is done, and to some extent with the grade of the slope, but the paving stone will average close to one-half cubic yard per linear foot, and spawl covering less than one-third cubic yard for a height of 16 feet between high and low water planes.

COST OF REVETMENT CONSTRUCTION.

Elements of work and cost in detail of 8,748 linear feet of revetment in Pelican Bend during the fiscal year ending June 30, 1900.

Classification and extent.

Cost in
item.

Total.

Grading bank (hydraulics), 8,550 linear feet, containing 60,452 cubic yards of earth:

Supplies.....

Subsistence

$391.62
500.03

Labor

1,585.98

Total cost, at $0.0409 per cubic yard

$2,477.63

Grading bank (slips and scrapers), 250 linear feet, containing 1,815 cui ic yards of earth:

29.44 207.35

236.79

Total cost, at $0.1304 per cubic yard..

Brush, 4,335.63 cords

4-inch strand, 72,144 pounds.

Cable clips,4,540..

Construction and anchorage of mattress, 8,975 linear feet, or 779,705 square feet:

9, 626.83
3,896. 72

227.00

Pine piling (dead men), 2,240 linear feet..

352.32

Subsistence

1,876. 42

Labor, weaving

4,420. 31

Grand total cost of 8,748 linear feet of revetment, at $6.10 per linear
foot

3,730.48 1, 368.84

53, 387.47

Cost of works on Missouri River.--The cost of standard pile dikes and revetments necessarily varies so widely in different situations that unit costs can not be definitely stated. The following are the principal elements which enter the question of cost: Difference in elevation of high and low water planes, height of bank, distance of work from base of supplies, plant charges, extent of work and degree of concentration of same, season of the year in which carried on, condition of flow.

For preliminary estimates, however, $10 per linear foot may be taken as the average cost of three-row dike work and of standard revetment, including all office and incidental charges.

In carrying on numerous works at widely separated localities it has been found that field charges are distributed about as follows:

For actual construction, 67 per cent.

For care, repair, and moving plant, 22 per cent. (This includes an item of but 5 per cent for light repairs. )

Administration, 9 per cent.

All other items, including surveys and travel, 2 per cent.

MISCELLANEOUS WORKS.

BBB 19.

IMPROVEMENT OF THE YELLOWSTONE NATIONAL PARK.

GENERAL:

*

[Officer in charge, Capt, Hiram M. Chittenden, Corps of Engineers.]

Main circuit or belt line.-As is well known, the object of the Government road system of the Yellowstone National Park is to give access to its natural wonders and attractions. The roads have no commercial purpose except such as may be incidental to this primary object. To a limited extent they may become thoroughfares for travel across the park both east and west and north and south.

While the entire region abounds in features of interest well worth visiting, there are six principal centers of attraction which are considered an indispensable part of every well-ordered tour. These are: Mammoth Hot Springs, the Norris Geyser Basin, the Firehole Geyser Basins, the Yellowstone Lake, the Grand Canyon of the Yellowstone, and the country near Mount Washburn and Tower Falls. The first three of these points of interest lie on a north and south line, approximately 20 miles apart. The other three lie on a similar line, 15 to 20 miles east of the first. A general circuit or belt line passes through these six centers, and at the points where the two sides approach nearest each other, namely, at Norris and the Grand Canyon, there is a crossroad connecting the two. The mileage of the belt line, including the crossroad just referred to, is about 154 miles.

Side roads.-Besides these more important points of interest there are many of less importance to which it has been considered necessary to build side roads. The principal side roads are as follows: Around

Bunsen Peak and to the Middle Gardiner Canyon, near Mammoth Hot Springs; the several side roads in the different geyser basins; the road to Sulphur Mountain in the valley of the Yellowstone River; the roads along both banks of the Grand Canyon of the Yellowstone; the road from Dunraven Pass to the summit of Mount Washburn, and the road from Baronett Bridge up the valley of the Lamar River to the northeast corner of the park. The total mileage of these side roads is about 62 miles.

Approaches. To give access to the park from the outside, and particularly to the main circuit of the road system, approaches have been provided on each side. The first of these and the most important, although the shortest, is that from the north, extending from Gardiner, Mont., to Mammoth Hot Springs. The importance of this entrance arises from the fact that it is at this point that railroads can approach nearest to any of the principal centers of interest, and also that Mammoth Hot Springs is the business and administrative headquarters of the park, and the only portion to which access can be easily had in the winter season. This approach is controlled by the Northern Pacific Railroad.

The eastern approach touches the belt line at the outlet of Yellowstone Lake, and enters the park by way of Shoshone River and through Sylvan Pass, in the Absaroka Range. From the eastern boundary of the forest reserve to the belt line the distance is a little less than 60 miles. About half of this distance is in the park proper. This approach is one of great scenic beauty, but owing to its length and the late melting of the snow in Sylvan Pass it can hardly become an important tourist route. It connects with the Burlington Railroad System.

"The southern approach touches the belt line at the west shore of the Yellowstone Lake and comes up from the valley of Jackson Hole, which, with Jackson Lake and the Teton Mountains, forms one of the most important scenic attractions in the entire Rocky Mountain region. The distance from the outlet of Jackson Lake to the belt line is about 45 miles. From the south boundary of the park to the belt line it is about 23 miles. This road connects with the Government road built under a separate appropriation as a military road between Fort Washakie and Jackson Lake, and thus gives access to the Wind River Valley. The southern approach has at present no railroad connection.

The western approach lies in the valley of the Madison River and its two tributaries, the Gibbon and Firehole rivers. It forks at the junction of these two streams and follows each to the belt line. The total distance from the west boundary of the park to the nearest center of interest, namely, the Lower Geyser Basin, is about 21 miles. This approach connects, through an outside road about 70 miles long, with the Oregon Short Line Railroad.

Mileage. The aggregate mileage of the park road system within the boundaries of the park is about 295 miles. The connecting Government roads in the forest reserve bring this mileage up to 405 miles.

It is not the policy of the Government to permit any undue extension of the road system, but to limit it to the actual necessities of reaching the more important objects of interest. So far as possible it is desired to maintain the park in its primitive condition without even the innovation of roads.

Trails. For access to those portions of the park which lie off the