cut away at 72 feet from the surface, where the soft part of the clay commenced, and a doom was constructed with brick and cement all round the exterior of the cylinder, with the intention of supporting the brick steining and strata above, and also to carry off the water, and prevent its softening the clay and the concrete. On the 18th of March, 1840, an internal cylinder of 2 feet diameter was lowered, within the original cylinder, and continued sinking until it reached the chalk, into which it was driven 4 feet ; the space between the large and small cylinders was then filled in with granite paving-stones for 5 feet in depth, and then with smaller stones, broken bricks, &c. mixed with hydraulic cement, to the depth of 25 feet, thus forming an effectual barrier against any future "blow" of sand from the original bottom of the well.

After all was imagined to be secure and the pumping had recommenced, a second separation, to the extent of 4 inches, was discovered in the cylinder. The gap thus formed was first filled in completely with wooden wedges, and a cast-iron cap was afterwards bolted within side. The well was then drained, and 400 holes,inch diameter, were drilled in the cylinder, immediately beneath the oyster bed, to admit the water from that level. It was ascertained also by experiment, that the quantity of water obtained from the 2-feet bore in the chalk, was about 22 gallons per minute. The bore was then continued for a depth of 200 feet, making the total depth of the well and the bore from the surface, nearly 400 feet, when a supply of water was obtained of 33 gallons per minute. Some of the joints of the cylinders were then picked out to admit the water, and, from all the sources combined, the quantity of water obtained was about 81 gallons per minute, or 135 barrels per hour; that is, 55 barrels from the chalk-spring, and 80 barrels from the sand-spring, per hour.

The cost of the well and the bore was £4444, to which must be added the expense of a 12-horse steam-engine and pumps, £1351, making a total cost of £5795.

Appended to the paper is the report of Mr. James Simpson, which gives a very clear account of the state in which he found the well, and the remedies which he suggested for the accidents. which had occurred.

It is illustrated by two drawings, showing in detail a vertical section of the well, with all the pumps and machinery, and also the tools used in the excavation and the bore.

SESSION 1843.

January 10.

The PRESIDENT in the Chair.

THE business of the meeting was commenced by reading an abstract of Mr. Davison's Paper, (No. 539,) describing the mode adopted for sinking a well at Messrs. Truman, Hanbury, Buxton, and Co's. Brewery, which was published in the Minutes of Proceedings of the session 1842, and the following observations were made.

Mr. Braithwaite described the difference between the method employed in sinking the well for Messrs. Truman and Co., and that for Messrs. Reid and Co. In the former the bore was small, and would, therefore, only produce as much water as was procured from the veins through which it passed vertically; while the latter, by its larger diameter, permitted lateral galleries to be driven in the direction of the fissures in the chalk: thus forming feeders for the well, and, at the same time, capacious reservoirs wherein the water accumulated when the pumps were not at work.

He attributed the comparative failure at Messrs. Truman's, to errors in the mode of sinking: the length of the cylinders which had been attempted to be forced down was too great, and the lateral pressure had prevented them from reaching the chalk; so that when the pumps were set to work, an undue quantity of sand was drawn up with the water, causing a cavity behind the brick-work, which at length fell in. The water having been pumped out to a lower level than was proper, the equilibrium between the water and the sand around the cylinder had been disturbed, and the "blow" of sand had ensued.

The New River Company had been advised to sink a well of sufficient diameter to enable them to excavate lateral galleries, but they had sunk their well in the Hampstead Road, of a small diameter, as described in the paper by Mr. R. W. Mylne, published in the third volume of the Transactions of the Institution; and although fissures had fortunately been traversed, which gave an ample supply of water, many of the difficulties encountered would, he contended, have been avoided by adopting the larger diameter, and sinking the cylinders into the chalk, before the pumping was commenced.

The supply of water at Messrs. Reid's well had been sensibly

affected by the recent proceedings at the Hampstead Road well, which was now being constantly pumped in order to sink it deeper.

Mr. Davison explained, that a bore of small diameter had been adopted, because it was calculated that a supply of water, sufficient for the wants of the brewery, would have been obtained by it. The excavation to within 5 feet of the chalk was suggested by the sudden dropping of the cylinder. He believed that when (contrary to his express instructions) the level of the water was reduced, by pumping, to below a given point, the sand from beneath the oyster-bed rushed in to restore the equilibrium within the cylinder, and thus caused the difficulties which he had to contend with.

During the last year the pumps had been at work 1616 hours, in which time 300,000 barrels, or 50,000 tons of water, had been drawn from the well.

Mr. Farey believed that the casualites in well sinking, generally arose from the sources which had been mentioned. Mr. Woolf encountered them when sinking the well at Messrs. Meux' (now Messrs. Reid's) Brewery. The pumping up of sand with the water, was there carried to such an extent as to cause an accumulation of sediment 2 feet deep in the liquor back, in 14 days, and ultimately the new well broke into the old one adjoining it.

Mr. Braithwaite explained, that in the year 1814, the well at Messrs. Meux' was pumped "to clear the spring," which caused a cavity of nearly 40 feet from the sides of the well, and endangered the stability of the buildings around. Piles were therefore driven to support the upper ground, and upon them the brick steining was carried up. If the cylinders had in the first instance been carried down to the chalk, before the pumping had commenced, this accident would not have occurred.

Mr. Vignoles remarked, that the same question, as to the relative merits of boring or sinking, had been discussed at Liverpool, for wells, in the red sandstone; and in practice it had universally been found that, by the latter system, the best supply of water had been procured, particularly when side-drifts had been made.

Mr. Mylne said, that the works at the well in the Hampstead Road, which had been repeatedly stopped from accident, were now resumed as an experiment. The quantity of water obtained was more than could be drawn by a pump 12 inches diameter,

6 feet stroke, making 10 strokes per minute (= 294 gallons per minute). The spring was struck at about 234 feet below the surface of the ground, and when the engine was regularly at work, the water generally stood at within 20 feet from the bottom of the well. He coincided in the opinion of the advantage of a well of large diameter over one of small bore, as it permitted side excavations to be made in search of water. This plan had

been pursued with success at Brighton.

Mr. Taylor observed, that another of the advantages of the large diameter was, that the proceedings could be watched, and accidents could be more readily remedied. The opinion of all practical miners was, that the large diameter was cheaper, as well as better, than the small bore.

Mr. Clark promised an account and drawings of a well now sinking by him at the Royal Mint. The advantages of a large diameter were manifest to all practical men, particularly when the auger, or "miser," was used, as it enabled the operation to be continued without pumping. The cylinders, in lengths of not more than 30 feet each, followed the "miser" down regularly, and as soon as they reached the chalk, the operation was considered safe; and as the "miser" did not excavate more than was due to the area of the cylinder, the equilibrium between the water within and the sand without the cylinder, was never disturbed. In a well sunk by him at Messrs. Watney's Distillery, the cylinders were 11 feet diameter. The "miser" used was 5 feet diameter, and was turned by twelve men at a time.

Mr. Braithwaite concurred in the advantages of using the "miser." He invariably employed it, and generally with

success.

66

Mr. Farey believed that the " auger," or miser," was first used in this country by the late Mr. Vulliamy, of Pall Mall, for sinking an Artesian well, into which there was an irruption or blow of sand, the effect of which was only overcome by this in

strument.

No. 548. "An Experimental Inquiry as to the Co-efficient of Labouring force in Overshot Water-wheels, whose diameter is equal to, or exceeds the total descent due to the fall; and of Water-wheels moving in circular channels."

By Robert Mallet, M. Inst. C. E.

This paper is partly mathematical, and partly experimental.

The investigation which it details, the results of which are given in ten tables of experiments, had in view principally to obtain the definite solution of the following questions:

1st. With a given height of fall and head of water, or, in other words, a given descent and depth of water in the pentrough, will any diameter of wheel, greater than that of the fall, give an increase of labouring force (i. e., a better effect than the latter), or will a loss of labouring force result by so increasing the diameter ? 2nd. When the head of water is necessarily variable, under what conditions will an advantage be obtained by the use of the larger wheel, and what will be the maximum advantage?

3rd. Is any increase of labouring force obtained by causing the loaded arc of an overshot wheel to revolve in a closely fitting circular race, or conduit; and if so, what is the amount of advantage, and what the conditions for maximum effect?

The author briefly touches upon the accepted theory of waterwheels, the experimental researches of Smeaton, and the recent improvements in theory, due to the analytic investigations of German and French Engineers.

Smeaton, in his Paper on Water-wheels, read to the Royal Society in May, 1759,-and Dr. Robinson, in his Treatise on Waterwheels, lay down as a fixed principle, that no advantage can be obtained by making the diameter of an overshot-wheel greater than that of the total descent, minus so much as is requisite to give the water, on reaching the wheel, its proper velocity.

The author, however, contends, that while the reasoning of the latter is inconclusive, there are some circumstances which are necessarily in favour of the larger wheel, and that conditions may occur in practice, in which it is desirable to use the larger wheel, even at some sacrifice of power; and that hence it is important to ascertain its co-efficient of labouring force, as compared with that of the size assigned by Smeaton for maximum effect.

The author states, first, the general proposition, that the labouring force ("travail" of French writers, or "mechanical power" of Smeaton,) of any machine for transferring the motive power of water, "is equal to that of the whole moving power employed-minus the half of the vis via lost by the water on entering the machine, and minus the half of the vis via due to the velocity of the water on quitting it." He deduces from the theory, the following results, coinciding with the conclusions obtained by experiment.