cession of operations of this kind the well is sunk and the steining carried to the required depth. On the other hand, if the steining is added from above, the curbs are supported by iron rods, fitted with screws and nuts from cross timbers over the mouth of the well, and as the excavation is carried on below, brickwork is piled on above, and the weight of the steining will carry it down as the excavation proceeds, until the friction of the sides overpowers the gravitating force or weight of the steining, when it becomes, as it is technically called, earth-bound ; then a set off must be made in the well, and the same operation repeated as often as the steining becomes earth-bound, or recourse must be had to the first method of under-pinning. Brick steining is executed either in bricks laid dry, or in cement; when the work is laid dry, a ring or two of brickwork in cement is often introduced at intervals varying from 5 ft. to 12 ft. apart to strengthen the work and facilitate the construction of the well. The bricks are laid flat, breaking joint; and to keep out moderate land springs, clay, puddle, or concrete, is often introduced at the back of the steining; for most purposes concrete is the best, as, in addition to its impervious character, it adds greatly to the strength of the steining.

The same measures are used in sinking iron cylinders as are adopted in sinking brick steining. Generally the cylinders are made of cast iron, either cast entire or built up of several shutters; the cylinders have internal flanges by which they are secured together, and which add very much to their strength; they are usually fastened together by bolts, and the joints are caulked with iron cement. Cylinders of this description, when they become earth-bound, can be driven so that they may be sunk to considerable depths without much trouble. The castiron pipes used in lining the bore-holes are put together with collars sunk into a recess at the ends of the pipes, or cylinders, and to which they are secured by countersunk screws, so that both the external and internal face of the cylinder is flush, and offers no impediment either to their being sunk or to the flow of water. When the supply is taken from sand it is usual to perforate the pipes, but this is not necessary in most strata; indeed, in the bore-holes in chalk and sandstone, or other strata that will stand without artificial support, it is not usual to line or stein except in cases where it is desirable to shut out some particular water.

BORING WELLS.

The art of boring wells is evidently more modern than the practice of sinking, yet it is of so remote a date that the precise period of its introduction is unknown. Wells that have been

bored are common in China, Syria, and Egypt; and many of them are supposed to have been executed 4000 years ago. In France, the earliest authenticated well is at Lillers, supposed to have been executed in 1126. In boring wells two systems have been adopted: one is called the Chinese system, and consists in having the boring tool attached to a rope; the other is the ordinary method, in which the boring tools are attached to a rod of iron or wood. Although these are the two primary ways adopted in boring, there are many modifications of them in practice combining one or other method; indeed, every engineer or contractor may have his own particular mode, or the circumstances connected with each work may demand the introduction of particular measures. (Plate 3, Figs. 2, 3.)

The method designated the Chinese is the simplest that is practised, as all the boring tools are attached direct to the rope worked vertically up and down, the torsion of the rope giving sufficient rotary motion to the tool to enable it to strike a fresh spot at every descent. The facility with which the tools can be raised by the rope in this system seems at first to commend itself; but in practice, when sinking deep wells, it is open to serious objections, as, owing to the flexibility of the rope, the tool cannot be properly guided, and the bore-hole is likely to become crooked, which would in time interfere with the working of the tool; and in cases where the bore is to be lined with pipes, would render difficult, if not prevent, their insertion.

The ordinary plan adopted in boring is to attach the tools to a rod, consisting of a number of lengths jointed together; a vertical and circular motion is given to the rods. In deep wells much time is necessarily lost in raising and lowering a long length of rod, either to change the tool or bring up the débris. Various attempts have been made to economise the time thus spent; as, for example, it has been proposed to make the tools slide upon the square boring rods, and by attaching them by chains or ropes to a windlass, when they require raising, it could be speedily done, as in the Chinese system; because it would not be necessary to unjoint the rods, as required when using the ordinary tool. Another method, patented by Beart in 1844, was to make the rod of the boring tube hollow, and into this tube to introduce water, which, ascending outside the boring tool, was to produce a sufficient current to carry the materials, loosed by the boring tool, to the surface. A very great objection to this method (even supposing it to be practicable) is the necessity of having a large volume of water, which generally in boring cannot be easily procured until the spring is tapped.

In boring deep wells the weight of the rod and the force of the momentum in falling are very likely to break the tools used,

or the rods themselves, when special provision must be made to prevent it. This has been attempted in various ways. Thus, wooden rods hooped with iron have been substituted for the iron bar-tubular iron rods have been used, having the same weight per foot as the ordinary bar, but having a greater area; when working in water they lose a portion of their weight, equal to the volume of water they displace. Both wooden and tubular rods will answer very well when the depth is not great, but when the depth is great they are not sufficient to meet the exigencies of the case. When a sliding joint is used (Plate 3, Fig. 4)-this joint was introduced by Euyenhausen, in Germany, M. Kind, in France, and in the system known as Kind's system in this country-any portion of the entire weight of the rods can be brought into action, as all those rods above the slide joint are counterbalanced by a weight suspended to a lever. In Kind's system the rods are often put in motion by a steam-engine, in the following way :-The rods are attached to one end of a lever resting on a fulcrum, the other end of the lever is attached to the piston-rod of an upright steam-engine; the valves of the cylinder are worked by a man; the rods are lifted by steam pressure and fall by their own weight.

The tools used in boring (Plate 3, Figs. 5 to 12, inclusive) differ according to the description of strata they are required to penetrate. Thus, when the strata is hard and compact, chisels of various descriptions are used to loosen the materials, which are either raised with an auger or shell pump, or miser. When the materials are of a soft nature, augers of various kinds are used. It very often happens that in deep borings it is almost impossible to escape breaking the tools used; when special instruments have to be used to raise them. (Plate 3, Figs. 13, 14, 15.)

TOWNS SUPPLIED FROM WELLS.

The art of well-sinking in a great measure may be said to be empirical, and it by no means follows that because water is procured in some places from wells and borings in sufficient abundance to supply a town, that water can be procured anywhere by sinking or boring, as it requires a combination of circumstances not generally met with to render the work successful; and as all theory when applied under unknown circumstance may lead to error, a collection of examples of wells in use at various places where water is raised for public purposes will be highly useful in guiding us in estimating the quantities of water likely to be procured under given circumstances.

Birkenhead, Cheshire, is supplied with water from two wells,

395 ft. deep, partly sunk and partly bored in the new red sandstone formation. From experiments made upon one of these wells, when the water level was 120 ft. from the surface, the well yielded 1,807,461 gallons in twenty-four hours; by lowering the head another 4 ft., the well yielded 2,000,000 gallons in twenty

four hours.

Braintree, Essex, is supplied with 45,000 gallons of water per day, from a well sunk and bored in the chalk. The well is 9 ft. diameter, and 55 ft. deep, with a bore-hole at the bottom 340 ft. in depth, making the total depth of the well 395 ft. In this well the water level has been observed to rise with every rise of the tide, which is probably due to the hydrostatic head created by the tide impeding the free flow into the sea of some under current, which is consequently dammed back, owing to the increased resistance offered to its escape.

Brighton, Sussex, is supplied with 1,080,000 gallons of water daily from wells sunk into the chalk.

Bury St. Edmunds, Suffolk, is partly supplied from two wells sunk in the chalk to a depth of 86 ft., and connected by headings. There is about 130 ft. of heading, 6 ft. x 6.5 ft., in connexion with the two wells. Very accurate observations have been made upon the level of the water in these wells by Mr. John Croft, in the year 1860, and continued to the present time, and are tabulated in Plate 4. Observations made by the same gentleman on a hundred private wells sunk into the superficial strata of the town show that the water level in all is very nearly the same, and varies in any case but a few inches. The wells upon which these observations have been made were sunk by the local authorities, not with a view of supplying the inhabitants with water, but for the purpose of procuring a supply of water for watering the roads, and other public purposes; but since the original construction of the wells a portion of the town has been supplied. The quantity of water yielded by these wells fluctuates greatly, and is dependent upon the season of the year. Thus upon one occasion, after a trial continued over seventy consecutive hours, the well yielded water at the rate of 150,000 gallons every twenty-four hours; but the ordinary quantity supplied is about 60,000 gallons per day.

Coventry, Warwickshire, is supplied with 750,000 gallons of water per day from two bore-holes made in the bottom of the reservoir, 100 ft. diameter; the bore-holes are respectively 6 in. and 8 in. diameter, and 200 ft. and 300 ft. deep. The supply is procured from the red sandstone; and, from observations made, it has been found that the two yield water at the rate of 700 gallons per minute.

Croydon, Surrey, is supplied from two wells sunk into the

upper chalk, one being 75 ft., and the other 150 ft. deep. The latter well was sunk by Mr. Thomas Docwra, under the author's direction; and although sunk but 56 ft. from the old well, it has been proved, by careful experiments, that there is very little communication between the main body of the water in the two wells. Thus, when water at the rate of 1,000,000 gallons per day was being raised from each well, the relative water level in the two wells was not the same, but was 7 ft. lower in the new well than in the old. By stopping the pumping operations in the new well, and continuing them in the old, the water level in the new well rose 5 ft. above the water level in the old well, proving the two wells to be independent of each other. The quantity of water yielded by the old well during the last dry summer was at the rate of 1,500,000 gallons per day, and was only limited to this quantity on account of an insufficiency of steam power to raise more.

Dorchester is supplied with 180,000 gallons of water per day, from a well 120 ft. deep sunk into the upper chalk; the well is furnished with four headings, having a total storing capacity of 70,000 gallons.

Eastbourne, Sussex, is supplied with 200,000 gallons of water per day, from two wells partly sunk and partly bored 125 ft. into the upper greensand; the wells are provided with a heading capable of containing 10,000 gallons; the bore-holes are 7 in. diameter, and 60 ft. deep.

Enfield, Middlesex, is supplied with 90,000 gallons of water per day, from a well sunk and bored 215 ft. into the lower chalk; the bore-hole is 12 in. diameter, and 201 ft. deep.

Fareham, Hampshire, is supplied with 200,000 gallons of water per day, from two wells 12 ft. and 9 ft. diameter respectively, which have an adit or heading in connexion therewith capable of containing 30,000 gallons.

Kingston-on-Hull, East Yorkshire, was formerly supplied with river water, but during the present year (1864) the town has been supplied with water raised from a well sunk at Springhead, and forced by steam power to the old works at Stone Ferry, a distance of nearly five miles, from which place it is again pumped and distributed to the town. The well is sunk and bored in the chalk to a depth of 281 ft. 6 in., of which 210 ft. is an 18 in. bore. The well itself is 14 ft. diameter, and steined partly with iron cylinders and partly with brickwork. At the present time the well is yielding 3,500,000 gallons for the supply of the town; the water available is estimated by Mr. Thomas Dale, the engineer for the works, as not less than 4,000,000 gallons in twenty-four hours. Owing to the large influx of water, and the position of the pumps, special measures have been taken by the engineer to