wise the mortar will not be of uniform quality, some portions being richer in cement than others.

The mortar should be used in the work as it is mixed, thus securing the first set of the cement in the masonry.

If an inspector is necessary on street improvements, it is much more important to have one on sewer work, as sewers are buried beneath the surface of the earth, and defects in material and workmanship not detected before they are covered, are liable to remain undiscovered until some portion of the sewer fails, when a large expense is entailed in making repairs.

For an inspector of brick sewers, an intelligent, competent mason should be employed, as he understands "the tricks of the trade" better than one who has had no special training in that line, and can more readily detect bad workmanship.

In connecting lateral sewers with the mains, the laterals should be constructed on such a curve that the flow from the lateral will be discharged in the direction of the flow in the main, otherwise an eddy will be formed in the main sewer, which will invariably cause a deposit, and consequently an obstruction.

Construct man-holes at all changes in the alignment of the sewer, and as much oftener as may be found necessary for proper inspection and care. In the case of pipe sewers (12-inch and over), man-holes from 150 to 200 feet apart will usually be found sufficient; while for brick sewers, it will not be found necessary to place them as close together as for pipe sewers.

CARE AND MAINTENANCE.-Sewers should be kept as clean and free from deposits as possible. For this purpose, occasional flushings should be resorted to, or flush tanks, located at the head of the lateral sewers, and discharging at regular intervals.

The outlets, if discharging into running or other water, should be placed sufficiently above the normal level of the water to insure their free and unrestricted discharge. When a sewer starts below or partly below the surface, the capacity of the sewer is decreased by the area occupied by the backwater from the lake or river, and the sewage coming from above, and discharged into this slack backwater, is there deposited, and so much of the sewer occupied by this backwater then becomes an elongated cess-pool, and an active factor for the manufacture of sewer gas.

The growth of willow trees should not be permitted in the vicinity of sewers, public or private: Experience has demonstrated that the two cannot live harmoniously together. The roots from the trees, if unrestricted, will enter, and in a short time completely fill, the sewer. To illustrate: In the summer of 1885, a 12-inch pipe sewer was constructed in one of the streets of East Saginaw. The pipe was laid at a depth of about 11 feet, in a stiff yellow clay soil; on one side of the street grew three medium-sized willow trees. During the past season this sewer was removed, to make room for a large main sewer; and, upon taking

out the pipe of the old sewer, it was found that the roots from these trees had entered the pipe, and a mass of roots, somewhat resembling a piece of cocoanut matting, 75 feet in length, 2 inches thick, and 15 to 18 inches wide, was removed from the sewer.

Many other instances of a like nature have come under the observation of the writer. In some cases, the sewers have been completely filled with the roots, necessitating the removal of the sewer, and the destruction of the trees.

In conclusion, it may be well to offer a few general

REMARKS.

The quality of the improvements to be made in the streets of a young city, will depend very much upon its natural resources, and the first improvements will be made with a view of reducing the first cost to the minimum. The city with age and population, will demand something better, more durable, and of necessity more costly, than that first adopted; and in time will probably go through the whole category of roads, from a cheap gravel or planked road to that of one of block stone or asphaltum.

Michigan having such an abundance of timber suitable for pavements, naturally that material is used very extensively for the improvement of the streets of its cities. Cedar seems to be the timber now most generally adopted for the better class of wooden pavements, but owing to its lack of durability (which is also true of any wood pavement), it is really one of the most costly which can be constructed.

Many of the eastern cities, notably Washington, D. C., have practically abandoned the use of wood, and are adopting other materials.

Washington, which previous to 1879 had over thirty-four miles of wooden block pavements, costing over $4,000,000, has quite abandoned its use; and has now almost entirely replaced the old pavements with stone or asphaltum.

Sanitarists protest strongly against the use of wood for paving, as being injurious to health, and with very good reason; wood being of such an absorbent nature, readily retains the liquid filth from the street, to be given off, during warm weather, in odors offensive both to the senses and to health.

But the fact is apparent that, so long as wooden pavements can be constructed so much more cheaply than those of a more durable and less objectionable kind, just so long will wood be used, yet in the construction of the pavements and the selection of the material, care should be taken to make them as durable as possible.

Cedar, as most generally used, is stripped of its bark, cut into suitable lengths, and placed upon the foundation prepared to receive it, retaining all the sap wood, the portion quickest to decay, and the portion which most readily absorbs the filth of the street. Remove the sap, and you remove the most objectionable part of the wood.

Experience has shown that the life of a pavement, constructed of sapless cedar blocks, is longer, and that the surface wears smoother and more uniform, than when the sap is left on; for the sap wood being first to decay, hastens the destruction of the rest of the block. Then again: the blows from the wheels of passing vehicles wear away the sap more rapidly than any other part of the block, thus forming depressions in which to hold the water and wash of the street, to be absorbed by the blocks, and giving to the whole a rough, uneven surface over which to ride.

It was the intention of the writer to dwell somewhat upon matters pertaining to sewerage and other municipal works; but this paper has already exceeded the limits originally assigned to it. One word more, however, to the engineers here assembled.

Remember, our calling is not only of an executive nature, but it is more exalted than that. If we do not administer directly to the moral welfare of our fellow-men, we should at least contribute to their physical well-being. We can do this by example as well as by precept. Convince him of the unsanitary conditions of his surroundings, and indicate the remedy; show him wherein the pollution of his supply of water for domestic uses lies, and how it leads to physical debility and death. By continuous and untiring efforts in the right direction, much can be done to improve the condition of those who live in our respective communities.

A man has never attained to his most exalted position until he ceases to be selfish, and works for the improvement and elevation of others. JOHN J. GRANVILLE.

Prof. Carpenter. "I found at Memphis that their sewer system has not a good reputation at home. They have flush tanks at the beads of the small laterals. They use the Fields flush tank, which is a simple affair, consisting of a siphon arranged at the side of the vessel, the water going out with a rush. They report it as somewhat uncertain in its action. The siphon does not always act, so that the water, instead of going out with a rush, goes out at the same rate that it comes in. The city engineer reports that the use of a tilting trap, and an inside lip which reduces the size of the siphon, will cause it to act."

Mr. Appleton. "Is there a deadener to this trap? They used the tilting traps in London years ago, and the noise of them was a great nuisance."

Prof. Carpenter. "It is not needed, being below the street." Mr. Appleton.- "There is a trap in this city having a movable bottom, which I put in several years ago, that has worked well, and never failed. It is not automatic, nor intended to act as an intermittent flushing trap. We do not put in a brick basin, because cement pipe is cheaper, and just as good. It is one thing that a cement pipe is good for."

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Prof. Carpenter. "Has Mr. Granville had any experience in the use of brick for pavement?'

Mr. Granville.-"I have not. I have received reports from Ohio engineers in regard to it, and samples of the brick used. It was not a vitrified brick. The trouble with brick pavements seems to be in the proper selection of the brick, to get them of a uniform quality. Some engineers retain a percentage until the pavement has been tested by one winter's frost."

Mr. Appleton "If ground slate is mixed with clay, it makes it perfectly durable, but the trouble is in a false economy which will not pay for the best."

Col. Muenscher.

in the brick."

Mr. Appleton.

"Some cities require a good deal of blue clay

"There must be a good deal of sand in a good brick, but it must also contain other material."

Prof. Carpenter. "I saw a good many samples of brick at the brick-makers' convention. I think we have no clay in Michigan suitable for such brick. They must be very hard, dense, and not vitrified. A vitrified brick is not so strong as one which is not. In Cleveland, brick is as cheap as wood, and it can be laid down in Detroit as cheap. They have good brick in Ohio."

Mr. Watkins.

"In a sanitary point of view, is not the vitrified brick the best, being less absorbent?"

Prof. Carpenter. "I do not know as there is any difference." President Steele. "I think we had better drop this part of the discussion here. We shall have the topic up later, in the paper from Prof. Greene. Have we anything in regard to other kinds of pavement, say of wood? In Traverse City, the streets are underlaid with sand. I don't know how deep. We have a pavement there which is a compromise between a stone pavement and a gravel road. The gravel packs very hard, and is very successful. We have plenty of cedar right at hand."

A. L. Reed." What sort of foundation is best for a block pavement?"

Mr. Granville. "It is best to put boards under blocks. The first block pavement we had in East Saginaw was put down without boards, and the blocks went down unevenly. We roll the streets with a ten-ton roller, put on three inches of sand, and then cover with inch boards."

Pres. Steele. "At Grand Rapids, they have cedar blocks on a gravel bed well rammed down, and covered with nothing but gravel well rammed. They have excellent drainage That may have a decided effect on the durability of the pavement, and speaking of that, if you want a durable plank, take one that has been in the mortar bed."

Col. Muenscher. "This system was introduced into Grand Rapids sixteen years ago, when I was city engineer, and 1 believe it is the best there is. You must have a good foundation. Excavate a foot in depth, and fill it with gravel, not sand. The blocks in this foundation have stood ten years without displace

ment. Leave the boards out when you have a clay bottom. The water runs through, and will rot the boards first. Then, too, the boards are always being cut and taken up, to make connections with gas, water, and sewer pipes, and can never be put back in good condition."

Mr. Granville.· "Right here is a point for criticism. In making sewer, gas, and water connections, the earth is softened. If boards are not put in, the blocks will go down. The boards will to a certain extent prevent that. If the blocks are well filled between with fine gravel tamped in, you have almost hermetically sealed the pavement, so that no water will go through. In East Saginaw we try to reduce the evils of taking up the pavement, by requiring people to make their connections the fall of the year preceding the paving of the street. If they wish to do it after the street has been paved, they are charged $25, to pay for the permanent damage to the pavement. We thus do not have much disturbance of the pavement. We take up a 16-foot section at a time, and never allow a board to be cut."

FREIGHT YARDS AND SIDINGS.

In looking over the reports of former meetings of this Society, I find several able and exhaustive articles on the location and construction of railways. There is, however, among others, one item which has been pretty much overlooked; that is, sidings and freight yards. They are not much thought of in the location of railways, and railway companies usually think that after a road is located and the main track laid, they can dispense with the services of most of their engineers; so the work is left to the trackmen, and the engineers are off to new construction. Consequently many of them have no experience in track work, and if by chance they are called upon to do such work, they are likely to commit blunders. This is one reason trackmen often have a contempt for engineer's stakes.

The locating engineer ought to have in mind the places where side tracks are likely to be put in, and then make the grades at such places as nearly level as possible. Serious accidents accompanied by loss of life have occurred from cars being started by the wind, and running out on the main track. This can be prevented by the stop-blocks in use on some roads, provided there is no neglect to put the blocks in place.

There should be as few switches as possible in the main track. Let the yard be developed from the side tracks.

There ought to be at least some attempt at uniformity in the laying out of the freight yards of any particular road. If there is a regularly organized engineer department, and the road master's