rope carriers. He wanted the best machine that could be built to do his work, and when the new system was offered was willing to give it a fair trial, provided the machine was so built that it could be changed to the fall rope carrier system if found necessary. This is the reason why the carriage and fall blocks, also the engine mentioned, were used, and why the Lidgerwood style of tower construction was followed. This condition in the contract was a serious handicap in the installation of the new system, and all the faults that can be found with the finished machine can be attributed to the use of parts of the older system.

The system used in this machine is what is known as the Laurent system, and the vital points of same are covered by Patent No. 653,698, which was issued to Louis E. Laurent, April 2, 1898.

The point made by Mr. Baldwin in closing his discussion about the improvements that have been made in fall rope carriers is well made, as the construction of the carrier itself is stronger and better designed to give longer service than those previously used; but that has nothing to do with the point made in the paper under discussion, which was that fall rope carriers of any kind largely increase the cost of maintenance and under all of the conditions for which cableways are designed are a very objectionable feature. This excessive cost of maintenance has been a bar to the introduction of cableways in many cases where they could have been used economically, and it is expected that the machine under discussion will prove that this item of expense can be largely reduced. This machine will have to handle about 100,000 tons of material, and an exact record will be kept of the work done and it will not be as "difficult to establish a comparison" as Mr. Baldwin seems to think.

XLV.

CONCRETE FACING ON A SANDSTONE BLUFF AT ST. PAUL, MINN.

ONWARD BATES, Mem. W. S. E.

Read 7th September, 1898.

The line of the Chicago, Milwaukee & St. Paul Railway Company in the city of St. Paul, beginning at the crossing of Chestnut street, extends with an ascending grade along the face of a bluff. This bluff is of a character common to the Mississippi River bluffs in that vicinity, and is composed of soft sandstone capped with an irregularly broken ledge of friable limestone, above which lie mixed together loose sand, gravel and boulders. This sandstone disintegrates readily, and is so soft that it wears away rapidly under the influence of the weather. The detritus from the bluff has frequently to be removed or it would cover the railway tracks, and the wearing away of the sandstone leaves the limestone ledge and the boulders which lie above it in a precarious condition, threatening the safety of trains on the tracks below. From time to time it has been necessary to build masonry walls on the face of this bluff for the protection of the railway tracks. The photographs submitted with this such masonry walls.

paper show

In the summer of 1897 it was decided to protect an additional stretch of the bluff, and the writer concluded to use a concrete facing instead of cut stone masonry, for the reasons which follow.

He assumed that the stability of the sandstone would be secured if it was protected from the rain and frost, and that a facing of concrete or brickwork would furnish protection equal to that of cut stone masonry, at a saving in cost. He had a precedent for this in similar work that he had put in at Fort Snelling to support some dangerous projections of rock under similar conditions. At Fort Snelling the danger seemed imminent and the overhanging rock was supported by brick buttresses or pilasters, and the adjacent bluff was covered with brickwork to shed the water from it. The Fort Snelling work had been exposed for three years and had served its purpose without signs of deterioration to the brickwork. At St. Paul he concluded that it would not be wise to make a smooth face to the bluff, because it would cost less to support the projecting limestone with pilasters than to remove it. If the projecting stone had been removed it would have resulted in loosening the adjacent stone and the excavation would have extended beyond the railway company's right of way into valuable city property.

A description of the work will be better understood by refer ence to the illustration.

In Fig. 436, the tracks shown in the foreground are those of the Chicago, St. Paul, Minneapolis & Omaha Railway Company, which are on the level bottom land at the foot of the bluff. The double track line of the Chicago, Milwaukee & St. Paul Railway Company lies on the bench which is supported by a retaining wall of stone masonry. At the left is shown a protecting wall of cut stone masonry. In the background is shown the work under discussion at an early stage of its progress.

The loose material was removed from the face of the bluff, and the next operation was to build brick pilasters under the projecting limestone. Three of these pilasters were built, the one nearest to the left is 6 ft. 0 in. wide and 4 ft. 3 in. thick; the second one is 12 ft. 0 in. wide and 4 ft. 9 in. thick; and the third one is 6 ft. o in. wide and 4 ft. 6 in. thick. The dimensions of these pilasters give an indication of the sizes of the stone projections which they support. While the work was in progress, a heavy section of limestone, located some 200 ft. from the left, tumbled down and temporarily obstructed the railway track, but its unstable condition was known and there was nothing in the way to be injured by its fall. By reference to Fig. 437, it will be seen that projecting bricks are built into the pilasters near their inner corners, which bind the pilasters and the concrete facing together.

The foundation for pilasters and concrete facing is in the sandstone, 4 ft. below the base of rail of the railway tracks, the footing course being 2 ft. deep and 10 inches wider than the wall above it.

The supporting frames for the concrete were put on in the following manner:

Bolts were put into the sandstone at distances apart of 8 ft., horizontally and vertically. With special augers holes were bored into the sandstone from 4 ft. to 5 ft. deep, inclining downwards so that the bolts would stand perpendicular to the face. The bolts were 3/4 in. in diameter and were placed in the holes with nuts on the lower ends, the holes being then filled around the bolts with mortar, a process easy of accomplishment on account of the downward inclination of the holes. The bolts projected about 18 in. beyond the face of the sandstone with their ends terminating in cast iron nuts of cruciform section, and with the threads in the nuts long enough to engage a second section of 34 in. bolt. This second section of bolt held the uprights in place. The uprights consisted each of two planks 2x8 in section with the bolt passing between them. The planking supporting the concrete was placed against the inner edges of the uprights. This framework was built up in horizontal sections, the uprights and planking used at the bottom being afterwards used again higher up on the wall. To remove the planking it was only necessary to unscrew the nuts which held the uprights, and when