SPECIAL WORKS.

Among the works of special interest, from a technical point of view, the following will be briefly described: The entrance gate at Gardiner, Mont.; the Golden Gate Viaduct; the Melan Arch Bridge over the Yellowstone at the Grand Canyon; the concrete dam, aqueduct, and fountain at Mammoth Hot Springs.

Entrance gate at Gardiner.-The importance of the northern entrance to the park is such that it was considered desirable to erect an entrance gate at that point. The Northern Pacific Railroad touches the park boundary at the same point, and the railroad company proposed, in the erection of their station, to combine it with the Government work in a manner to give an effective approach for tourists coming from that direction. The conformation of the ground lent itself admirably to this purpose. The railroad was made to terminate in a loop practially tangent to the boundary of the park, and the Government road likewise terminates in a loop tangent to the boundary at the same point. Between the two the station is located, with a long train platform on one side and a coach platform on the other. The space within the loop of the Government highway has been converted into a small park, planted with shrubbery, and ornamented with a small pond, both of which are sustained by water brought from the Gardiner River.

The station is a unique and interesting structure, built after the design of Mr. R. C. Reamer, an architect of great originality, and particularly skillful in adapting his work to natural surroundings.

The loop and park are in a depression in the hills, around the sides of which the road rises from the level of the station platform to a height of about 30 feet at the neck of the loop. Across this neck the entrance gate, in the form of a large stone arch, has been built.

The gate consists of two square stone towers, with a batter of 1 in 30, the bottom dimensions being 12 feet 8 inches square. The clear space between the towers at the ground is 19 feet 8 inches. It is closed over by an arch, the crown of which is 30 feet above the ground. This arch curtain is 5 feet thick, and is built up to the same height as the towers. The entire structure is 50 feet high, and is capped with a concrete roof, roughly shingled with the chippings from the cut stone used in the arch.

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The character of the masonry is entirely original. It consists of columnar basalt, taken from a quarry near by, in approximately hexagonal prisms. These have been used just as found, with the least sible dressing, retaining their natural weather-worn condition. The points of the prisms project beyond the plane of the face and give to the whole structure a novel appearance as a masonry work. The two base courses are roughly cut, as, of course, are the stones in both the small and the large arch rings. The cutting of this stone was a very difficult matter, owing to the extremely hard quality of the rock.

The side of the structure which faces the station is ornamented with three tablets. The largest is 3 feet 10 inches by 20 feet 8 inches, and bears the inscription, "For the benefit and enjoyment of the people”— an extract from the act creating the park. The smaller tablet on the left tower is inscribed, "Yellowstone National Park;" that on the right, "Created by act of Congress March 1, 1872." These tablets were molded entirely of concrete. The forms for the letters were manufactured by the Stillwater Manufacturing Company, of Stillwater,

Minn., and were cut out in reverse with great accuracy. They were made so as to give a depressed letter in the concrete, and with a triangular cross section, so as to be easily removed after the concrete was set. They were nailed upon a suitable frame, which was placed in position to close a recess left for the purpose in the masonry. For the larger tablet this space was 18 inches deep-that is, 18 inches from the face back into the wall.

The concrete used was in the proportions 1, 2, and 4. A mortar facing was put in at the same time, sufficiently thick to cover the letters. The concrete rested directly upon the masonry below it. As soon as the space was filled, and before the concrete had set, the course of stones above was laid upon it, so that their weight pressed into the block, making a perfect bed. The forming was held in position by means of rods previously laid in the walls.

Extending from the tower of the arch in both directions for a distance of about 30 feet are two wing walls 12 feet high, terminating in square towers about 14 feet high. From these towers walls 8 feet high extend along each branch of the loop to the park boundary.

Golden Gate Viaduct.-The Golden Gate Viaduct is a concrete structure designed to carry the road around the face of a nearly vertical cliff. The question of choice of material turned both upon the general appearance of the structure and the necessity of making quicker work than the condition of the steel market would permit if steel were used. To have built a steel structure would have required accurate surveys and close examination of the foundations, including borings, which, together with the great difficulty of securing prompt deliveries of steel, would have made it practically impossible to erect the work during the season in which it was felt it should be erected. With concrete, on the other hand, surveys of the foundation could be omitted, because it was only a question of using a little more or less concrete, according as it might be found necessary to carry the piers more or less deep into the rock. It was much easier, moreover, to get prompt cement deliveries than steel. Finally, it was believed that a series of arches built against the side of the cliff and fitted to the natural face of the rock would produce a more pleasing effect than a steel structure. For these reasons concrete was adopted.

The viaduct consists of eleven arches resting on two abutments and ten piers, the whole being on an 8 per cent grade and on a 10° curve. The radius of the outside of the parapet wall is 573 feet. The length on center line is 200 feet, and the abutment wing walls extend 12 feet farther at each end. The arches are terminated at their inner extremities by the irregular and nearly perpendicular face of the cliff, leaving a roadway averaging about 18 feet in width. The piers are spaced 18 feet center to center on the outside and converge 64 inches in 18 feet. They are 3 feet thick. The arches are 18 inches thick on the pier, 12 inches at the crown, and have 24 inches rise. Piers and arches are built of Atlas Portland cement concrete, the former in proportion of 1, 2, and 4, and the latter in proportion of 1, 2, and 3. In the crown. of each arch is embedded a piece of wire netting, 7 by 15 feet, made of No. 8 B. W. G. wire, meshes 24 by 5 inches, the long dimension of mesh and short dimension of the piece of netting being parallel to center line of bridge. The piers rest upon horizontal surfaces stepped into the solid rock, and where these footings are separated by surfaces inclined much from the vertical anchor bolts were embedded in them.