mented with in New York. The results were not satisfactory; the muddy water collected in puddles in the hollows of the pavement, and the amount of mud and silt carried into the sewers threatened to soon choke them up.

This method is specially applicable to impervious pavements, such as asphalt and stone blocks and brick with water-proof joints. Wood pavements when they become covered with sticky mud are more easily cleansed by washing. In washing asphalt the sludge formed should be removed by the use of rubber squilgees; their use will also hasten the drying of the surface.

911. Street Sprinkling.-Streets are sprinkled with water for the purpose of laying the dust and cooling the air.

Two methods of applying the water are practised: (1) by hose attached to the fire-hydrants, and (2) by specially constructed carts.

The carts are preferable to the hose method; with the latter there is less regular distribution of the water, and in some localities there may be pressure enough to cause injury to the pavements. Again, the hydrants are generally located so far apart that long lengths of hose are required, and the constant rubbing soon wears them out. To obviate this metal pipe is employed in Paris; the pipes are usually in lengths of 6 feet, mounted on two-wheeled trucks, and connected by flexible joints.

Carts cause less interruption to traffic, require less time and fewer men; moreover, when there is a scarcity of water they may be filled from wells or rivers.

912. Systems. Three systems are practised for carrying out the work of sprinkling: (1) by the municipality, with its own equipment and men; (2) by contract, the contractor furnishing the labor and equipment; (3) by contract for the labor, the city furnishing the carts. The first system is generally the most satisfactory.

913. Quantity of Water required.-The quantity of water required will vary greatly, depending upon the character of the pavement and the temperature. The average number of gallons used in the United States per 100 square yards is 250; in Paris about 120 gallons per square yard; in London about 150 gallons.

914. Frequency of Sprinkling.-The frequency of sprinkling will depend upon local circumstances. In Berlin all the streets are sprinkled twice a day from April 1st to October 1st, and the principal thoroughfares and squares are sprinkled three and four

times per day in this period. For this work the contractor receives on an average $1.68 per day for each wagon. About 150 sprinklingcarts are used, each holding about 950 gallons. The street-car companies share the expense of sprinkling the streets occupied by their tracks.

In American cities the frequency of sprinkling the streets varies with the locality and the 'seasons of the year. The general practice appears to be about as follows:

Paved streets are sprinkled twice a day during the months of March, April, and November, three times a day during May and October, and four times a day during June, July, August, and September.

Unpaved, macadamized, and gravelled, streets are sprinkled twice a day during the months of March, April, May, October, and November, and three times a day during June, July, August, and September.

It is not usual to sprinkle the streets on Sunday, but in some few localities boulevards and driveways used on that day are sprinkled once or twice.

915. Cost of Sprinkling. The cost of sprinkling is variable, depending upon the time occupied in travelling to and from the points. where the water is obtained and where it is used. The range appears to be from 4 mills to 7 cents per 1000 square yards sprinkled.

916. Sea-water and deliquescent salts (as the chloride of calcium) have been used for street sprinkling. The surface is kept moist, but at the expense of the moisture in the air, and it is said that horses, hoofs are injured by the chemicals.

CHAPTER XX.

TREES.

917. OPINIONS differ as to the desirability of trees on roads and streets. Some claim that they do more harm than good; that they impede the circulation of the air, and that, as far the shade they afford, people who do not like sunshine have only to keep on the shady side of the way; that they deprive the road-surface of the drying action of the sun and air, and that in wet weather the constant dropping of water from their branches keeps the road in a muddy state. Others claim that trees, especially in streets, temper the heat and serve as a protection against dust, that the evaporation from their leaves tends to keep the surrounding air cool and moist; that the perpetual vibration of their foliage and swaying of their branches, whilst admitting a sufficient amount of light, serve to protect the eyes from the noonday glare; that they act as disinfectants by drawing up and absorbing the organic matters contained in the filth from which the streets of a town are never free and which, infiltrating the ground, are a frequent cause of fevers and infection; and it is asserted that on soil roads some varieties of trees both drain the road and help to hold its earthen surface together by their root-fibres.

"Those who have observed woodland roads closely know they are dry except when below the general grade of the land or actually swamped with water. At any point of temperature a tree, even in winter and without any leaves upon it, is evaporating moisture from its twigs, branches, and trunk. It must freeze very deep to prevent all root-action, and whatever moisture roadside trees may draw from the roadbed will, by so much, prevent the tendency to muddiness in any loam road well filled with tree-roots."

"Beside the draining and drying effect of tree-roots, the fibres

given to the soil by some kinds of trees (well known to ploughmen in all countries) have a most salutary effect in holding the earth together. If the soil be rich, the whole substance of the raised and rounded roadbed may be completely filled with horizontal stitches, as the housewife darns and runs the heels of stockings, thus trebling their ability to resist friction. Roots in the surface-soil are better than brush to hold up travel when they are alive and pumping water out of the ground. If we are looking for economy, nothing can be cheaper than the way a maple, elm, cottonwood, or white pine will fill the surface of an earth road with fibre. The chestnut, hickory, ash, black walnut, and beach may all be thought of in this connection, but only the close student of nature and the variety of trees adapted to different soils and situations will succeed in this branch of road-making. Yet the nation has many thousand miles of muddy highway where no other improvement seems possible."

"There is a use for the overhanging branches of trees in winter. They shade the road and permit it to freeze or remain solid when, but for the shadow, the road would be softening in the sun. The branches work in this way to prevent and protect the road from being cut in pieces. The traveller and his weary team, swamped in thawed earthen roads, are glad to reach the frozen track on the north side of a bit of woodland. And the man who would cut away roadside shades so as to let all our earth roads thaw out and settle together is very much mistaken."

Trees also serve to make the border of the road discernible at night as well as after snowdrifts, thereby warning the travellers against embankments and other dangers along the sides of the road.

918. In France, as far back as the middle of the sixteenth century, trees were planted along the royal roads. This practice has been more or less continuously followed.

During several periods it was stopped by those in authority, they being of the opinion that trees were more of a damage than a benefit. But now trees are planted along all roads having a width greater than 10 metres (32.8 feet). They are placed at distances. varying from 5 to 10 metres (16.4 to 32.8 feet), in single rows upon the narrow roads, and in double rows upon the wider.

919. "The roads of Belgium are flanked on either side by two and sometimes four rows of shade-trees, which add much to the beauty of the country through which they run."

920. Financial Value of Trees.-Take two streets in all respects alike, except that one has trees well selected, set at suitable distances apart and well cared for, the other with no trees or with trees carelessly set and neglected, as frequently happens. A person wishing to purchase a residence will undoubtedly select the street having the fine trees, although he may have to pay more than many times the cost of the trees. Thus from a financial standpoint trees pay.

921. In Saxony a considerable revenue is derived from fruittrees planted on the roadsides. The trees are cared for by the roadmen in so far as professional knowledge is not required; they remove insects, clear the tree-frames of rubbish, and water them.

In sections where fruit-trees cannot be cultivated on account of climatic causes, or where they would be liable to wanton damage and plundering of the fruit, forest-trees are planted.

The state-road fruit-trees are leased to the highest bidders, and the money received is covered into the state treasury. The lessees of the fruit-trees are held to a strict account for any damage done the trees. Ladders must be used to gather the fruit, and any battering of the trees with clubs or poles to get the fruit down is prohibited and is punishable by fine.

922. Selection of Trees.-Trees should be selected with reference to the climate, locality, quality of soil, extent of space, and circumstances of surroundings in general.

Large-growing varieties should be selected for places of great extent, smaller varieties for places of less extent. A low compact tree is not suitable for street planting.

The qualities necessary in a good street tree are that it must be hardy, must not be affected by a long-continued drought, heat must not wither it nor make it look rusty; it must be able to withstand dust, smoke, soot, foul air, and the insidious attacks of insects, and be able to recover from any malicious or accidental injury it may receive.

The tree must be of rapid growth and develop a straight, clean stem with shady foliage. It must be graceful either in full leaf or when bare, as in winter; its roots must not require too much. room, and they must be able to withstand the effects of pollution or rough treatment.