will refer our readers to several English authorities for views on this subject. Gisborne says:

Mr.

"We were astonished to find, at the conclusion of Mr. Parkes' Newcastle Leeture, this sentence: It may be advisable for me to say, that in clays, and other clean-cutting and firm-bottomed soils, I do not find the collars to be indispensably necessary; although I always prefer their use.' This is a bare faced treachery to pipes an abandonment of the strongest point in their case-the assured continuity of the conduit. Every one may see how very small a disturbance at their point of junction would dissociate two pipes of one inch diameter. One finds a soft place in the bottom of the drain, and dips his nose into it one inch deep, and cocks up his other end. By this simple operation the continuity of the conduit is twice broken. An inch of lateral motion produces the same effect. Pipes of a larger diameter than two inches are generally laid without collars; this is a practice on which we do not look with much complacency; it is the compromise between cost and security, to which the affairs of men are so often compelled. No doubt a conduit from three to six inches in diameter is much less subject to a breach in its continuity than one which is smaller; but when no collars are used, the pipes should be laid with extreme care, and the bed which is prepared for them at the bottom of the drain should be worked to their size and shape with great accuracy.

"To one advantage which is derived from the use of collars we have not yet adverted-the increased facility with which free water existing in the soil can find entrance into the conduit. The collar for a 1 inch pipe has a circumference of three inches. The whole space between the collar and the pipe on each side of the collar is open, and affords no resistance to the entrance of the water; while at the same time the superincumbent arch of the collar protects the junction of two pipes from the intrusion of particles of soil. We confess to some original misgivings that a pipe resting only on an inch at each end, and lying hollow, might prove weak, and liable to fracture by weight pressing on it from above; but the fear was illusory. Small particles of soil trickle down the sides of every drain, and the first flow of water will deposit them in the vacant space between the two collars. The bottom, if at all soft, will also swell up into any vacancy. Practically, if you re-open a drain well laid with pipes and collars, you will find them reposing in a beautiful nidus, which, when they are carefully removed, looks exactly as if it had been molded for them."

Mr. Denton says:

"The use of collars is by no means general, although those who have used them speak highly of their advantages. Except in sandy soils, and in those tha

are subject to sudden alteration of character, in some of the deposits of red sandstones, and in the clayey subsoils of the Bagshot sand district, for instance, collars are not found to be essential to good drainage. In the north of England they are used but seldom, and, in my opinion, much less than they ought to be; but this opinion, it is right to state, is opposed, in numerous instances of successful drainage, by men of extensive practice; and as every cause of increased outlay is to be avoided, the value of collars, as general appliances, remains an open question. In all the more porous subsoils, in which collars have been used, the more successful drainers increase the size of the pipes in the minor drains to a minimum size of two inches bore."

CHAPTER II.

SIZE OF TILE, ETC.

The size of tile to be employed in underdraining depends upon, 1, the amount of fall; 2, the length of the drain; 3, the distance between the drains; 4, the depth of the drains.

It is very evident that the greater the amount of fall, the smaller the conduit may be; and the converse of this proposition is equally true, viz: that the less. the amount of fall, the larger the pipe must be. Actual experiment has demonstrated that if a drain of 100 feet in length, having eight feet fall, is laid with pipe having a caliber or capacity of 14 inches, will in twenty-four hours drain the same quantity of water that 2 inch pipes, having a fall of 2 feet 3 inches, will drain in the same period, or a 3 inch pipe having a fall of only 6 inches, or a 4 inch pipe having a fall of less than 3 inches. Hence the size of the tile is determined by the amount of fall.

Again, it may be necessary to discharge 50,000 gallons of water in 24 hours, where only 2 feet fall in 100 feet in length can be had; a 3 inch tile with 1 foot fall will effect this, but if 2 inch tile were employed, it would require a fall of 4 feet 6 inches. Hence the length of the drain, or what is the same thing in effect, the amount of water to be discharged, governs the size of the pipe.

If 50,000 gallons are discharged by each of the two drains, A and B (Fig. 30), 100 feet apart, it is evident that if a third drain, C, were placed between them so as to make the distance between the drains 50 feet, then each drain would discharge 33,333 gallons. But if two more drains, D and E, are placed between A and C, and C and B, then the distance between the drains will be 25 feet, and the amount discharged by each drain will be 20,000 gallons only.

If, then, the drains are made 25 feet apart, 2 inch tile, with a fall of 9 inches in 100 feet, will drain off as much water as A, B and C would with the same sized tile, having a fall of 2 feet, or 3 inch tile, having a fall of 5 inches. Or if the two drains, A and B, only are employed, then if laid with 2 inch tile, they must have a fall of 4 feet 6 inches; with 3 inch tile a fall of about 1 foot; or a fall of 5 inches if 4 inch tile are employed. Hence the distance between the drains determines the size of the pipes.

From these propositions it is very evident that the depth of the drains exerts a controlling influence on the size of the pipes.

Suppose the drain 7, 5, in Fig. 31, were placed no deeper than the point indicated 8, it is very evident that in such case it would have less than half the amount of water to drain that it has at 7.

As the entire efficiency of drains depends upon a correct understanding and compliance with the principles involved in the four propositions stated at the commencement of this chapter, we shall dwell at some length upon them.

Stone drains require more fall than tile drains, on account of the friction, or the retardation water meets in passing through angular crevices. Friction must not be omitted in our calculations of fall and capacity. Where water can flow in

a straight direction in a smooth and regular channel, much more water can be discharged in a given time than where the angles and curves occur in the direc

tion; and where the surface is smooth, the flow is more rapid than where it must pass through a channel full of rough points or inequalities.

In some recent English experiments "it was found that with pipes of the same diameter, exactitude of form was of more importance than smoothness of surface; that glass pipes, which had a wavy surface, discharged less water, at the same inclinations, than Staffordshire stone-ware clay pipes, which were of perfectly exact construction. By passing pipes of the same clay-the common red clayunder a second pressure, obtained by a machine at an extra expense of about 18 pence per 1000, while the pipe was half dry, very superior exactitude of form was obtained, and by means of this exactitude, and with nearly the same diameters, an increased discharge of water of one-fourth was effected within the same time. "On a large scale, it was found that when equal quantities of water were running direct, at a rate of ninety seconds, with a turn at right angles, the discharge was effected in one hundred and forty seconds; while, with a turn or junction with a gentle curve, the discharge was effected in one hundred seconds."

CALIBER AND MINIMUM FALL OF DRAN PIPE TILE.

Vincent, an English writer, has adopted Eytelwein's formula,

=

in the computation of the minimum fall and caliber of the pipe tile. In this formula, c velocity of current per second, d = diameter, or caliber of pipe, and h the fall in 1 foot, as data from which to determine the velocity of the water in a pipe of a given diameter, and given fall. He determined from this formula, by an inverse process, the requisite caliber of the pipe tile d, for a given distance or length of drain-assuming six inches per second to be the minimum velocity of water discharged from an acre. The calculations in question were, however, based on hypothetic values only; because the co-efficient, 50, occurring in the formula, refers, originally, to metal tubes or pipes; and there was no data at hand for that of clay or earthenware pipes. Owing to the great importance of having the pipe tile of proper caliber, John, Waege, and v. Möllendorf,* made a series of experiments.

For this purpose they laid a number of drain tile in a trough making a slight angle with the horizon, and secured the joints by moist clay. Water was then let into the pipe from a reservoir, and the time occupied in flowing through the

* These experiments are quoted in detail in Zeitschrift fur Deutsche Drainirung, 1855, pp. 79 and 106; also in Dingler's Polytechnische Journal, 138, 257.

pipes in seconds and the quantity discharged in cubic feet was very carefully observed and recorded.

The data obtained from repeated observations, with given lengths of pipe and various degrees of inclination or fall, and various capacities or diameters of pipe— and notwithstanding that the extremes of twenty-two experiments varied about 40 per cent. sufficient data was obtained to change the co-efficient 50, and to make the following as nearer the truth, viz:

If we adopt Vincent's data, and assume that the velocity of water, in pipe tile, amounts to 6 inches per second, as a minimum, in order to secure the pipes from being filled by detritus, or particles of earth entering them and being deposited by gravity overcoming velocity, then the following will be the minimum fall (by Vincent's formula) for drains of 120 feet in length:

For drains with tile of 1 inch caliber, 2.33 inches fall (4.8)

The figures in parentheses are those adopted by Vincent. It must be remembered, however, that these figures are applicable only to such drains as are as good and as carefully laid pipes as those in the experiment.

In calculating the capacity of drain pipe tile, two other contingencies must be taken into account, namely: the quantity of water to be discharged, and the distance between the drains. Upon the supposition that well-arranged drains must discharge the rainfall of a month in fourteen days (assuming 4 inches as the maximum), Vincent has fixed the amount discharged per second, from an acre, at 0.00625 cubic feet.

In the course of several articles in Zeitschrift fur Deutsche Drainirung, John has compared the replies of several writers to the question, "What is the capacity of pipe tile of a given caliber ?" Schönermark, the practical draining engineer of the Duchy of Brunswick, has communicated some calculations upon

* Agronomische Zeitung, 1855, page 360.