Eight inches from the open end of the blow-pipe A, a glass tube B, an inch and a quarter bore, and 28 inches long, was secured in a frame. Its lower end descended into a vessel of water, as represented, and to its upper end was fixed a ferrule i, of tin plate. To this ferrule the vertical tubes of the caps were accurately fitted, so as to be slipped on and off without disturbing B. The models were made of tin plate, and the vertical tubes attached to them were all of the same dimensions, viz.: 14 inch long and 1 inch bore. The glass tube which may be supposed to represent a chimney, was designed, as the reader will have already perceived, to measure the degrees of rarefaction produced within it by the caps-the ascent of the fluid indicating the effect of the blast of wind on each. Except when otherwise noticed, the axes of the caps, or horizontal tubes, were made to coincide with that of the current. With the view of verifying the general results, and to detect any variation in the force of the blast, from slight changes in the speed of the steam-engine, the experiments with each cap were repeated, at short intervals of time, but no very obvious changes in the results here recorded were observed.

Experiment I.-The first experiment was with the tube B, as figured in the cut. It was raised till the orifice of the ferrule was in the centre of the blast; but in no part of the current was any rarefaction produced. The water was neither elevated nor depressed within the tube. Had the upper end been inclined towards A, wind would have entered and displaced the water from the bottom of the tube: and, on the other hand, had it been inclined in the opposite direction, a slight ascent of the fluid would have followed; but it was not deemed of sufficient importance to try either.

Experiment II.-The tube C was now slipped on the ferrule in the position in which it is figured. It will be perceived

It

Experiment III.-D was next tried. consisted of two tubes like C, united at right angles. When the horizontal branch was in the direction of the current, the water oscillated in the tube from 1 to 24 inches. Upon turning the cap till its axis formed an angle of 45 degrees with that of the current, the liquid column rose to 3 inches; and when the angle was 90 degrees, the water fell to 24 inches. An elevation, however, greater than was obtained when the cap ranged with the blast. The cap was next turned to its first position, and a conical tube, 6 inches long and 2 inches diameter at its wide end, added to it, as figured at E. To our surprise, no further elevation of the fluid took place. The central current of the blast being received against that part of the vertical tube opposed to it, was, probably, too strongly deflected to allow other portions of the current to sweep close around the horizontal branch. Had the cap D resembled the one marked F, there can be no doubt of the effect being increased, as the wind would then embrace, and impinge upon, a larger surface. Unfortunately we had not prepared any models of cylindrical caps at various angles, i. e., where the caps proper were inclined upwards like F. The next figure exhibits an approach to this plan, and when compared with C, which it so nearly resembles, exhibits a decided improvement.

Experiment IV.-The cap G consists of a vertical tube, with a head piece extending over three-fourths of its upper, or discharg ing, orifice. The back of the hood, which receives the blast, forms an angle of about 30 degrees with the side of the pipe to which it is attached. This cap raised the water in B from 3 to 4 inches, being double the elevation which C produced. Deviating the position of the opening, with regard to the current, diminished the effect.

Experiment V.-The conical cap H was now placed in the blast, upon which the fluid ascended in B from 2 to 3 inches. Three models of this cap were tried; they were all of the same diameter at the mouth, and the vertical tubes were attached to them at the same distance from the mouths, viz.: ths of an inch; but their lengths varied, being respectively 3, 3, and 3 inches. There were no very observable variations in the altitude of the liquid column produced by them, but the only one that raised it to 3 inches was the longest-the one last named. When the mouths were turned till the axes of the cones formed an angle of about 45 degrees with that of the blast, the water commonly fell in the tube, though not uniformly so; but what appeared singular, when the axes of the cones were at 90 degrees with the current, the water actually rose to 4 inches! On several trials this unexpected result followed.

was made from caps on sale in the city. The outer pipe, or case, was 4 inches long and 1 inch bore. The inner tube was 4ths of an inch bore, and with the eonical ajutage to catch the wind, 2 inches long. This cap raised the water 4 inches. When its axis was a little inclined to the blast, no sensible change in the elevation of the water in B followed; but when the angle with the axis of the blast was at 45 degrees, the water fell to 3 inches, and at 90 degrees the water stood only at an inch. (This, and the remainder of the figures, are in section.)

Experiment VII.-The inventor of the last cap has applied near its open end (by two or three strips) a cone, as represented at J. The object of this is to prevent currents of wind entering that end, and so driving the smoke down the chimney, instead of drawing it up. To ascertain the effect of this arrangement on the exhausting power of the cap, the model J was made in all respects the same as I, the cone excepted. On applying it to the current, the water rose in B to an elevation little more than half of that produced by I, being only 24 inches. When the cap was turned to 45 degrees, the water fell to 14 inches, and at right angles it sunk to a level with that in the vessel. This effect might in some degree have been anticipated, since the wind would, in being thrown from the sides of the tube, be apt to catch hold of the cone, and be turned into the cap. On this account, the base of the cone should not project in the least degree over the mouth. The cone, too, retards the free exit of the smoke.

Experiment VIII.-The next devices tested were such as I have applied to charge siphons, and also for producing a vacuum by currents of steam-the model marked K consisting of a horizontal and perpendicular tube of the same bore, united at right angles. The horizontal one was 24 inches long. On placing this cap on the glass tube, no rise of the water took place, but rather the reverse, for portions of wind descended and drove out the water occasionally. When the axis was inclined nearly 45 degrees to the blast, the water rose four inches. At right angles it was two inches.

A projecting piece was now placed within the cap, so as partly to cover the orifice of the perpendicular tube; (see next figure, marked L.) On trying this, the water rose 44 inches; inclining the cap raised it to 51 inches; as the projecting piece retarded the current through the tube, it was pressed down to make the passage way larger, upon which the water rose a little higher. Various conical ajutages were now tried, as figured at M, and with one 6 inches long, and 2 inches diameter at the wide end, the water rose 81 inches. No additional rise of the columa was obtained by changing the position of the cap within the current.

Experiment IX.-The same cap was now tried again, but with the projecting piece entirely removed, (see N.) The water now rose 15 inches, and oscillated from 13 to 15. A short conical tube, whose mouth flared out to 2 inches, was next inserted into the small end of the cap, with a view to draw more air through it; this caused the liquid column to ascend at once to 18 inches. A longer tube, whose mouth reached to the orifice of A, caused the water to rise entirely out of the tube-28 inches! These increased defects, it will be remembered, are caused by an interior and exterior blast-the wind sweeping over, as well as through, the cap.

Experiment X.-A cap, precisely the same as the last, except the horizontal one, being 11⁄2 inches bore, and as figured at O, raised the water to 18 inches, and kept it oscillating from 16 to 18. The short diverging mouth

piece mentioned above, was applied to the receiving end of the cap, and raised it from 22 to 24 inches!

From these experiments it would seem that a chimney cap, or ventilator, made like the last figure, is very far superior in its effects to any other yet known; and, what is of some consequence, the form is almost as simple as the simplest. A diverging tube might be attached to the end which receives the current, but the mouth of this should not greatly exceed the diameter at the junction with the vertical tube; if it did so, it would diminish the effect of the wind, in sweeping along the sides of the discharging branch. The under side of the receiving end of the cap should project beyond the upper one, in order to catch the descending currents more readily. This feature is figured at N and O.

Perhaps some readers of the Journal may find time to repeat and extend these experi

ments. There are several old chimney caps which have not been included, especially revolving ones At the first favourable opportunity, we will, if not anticipated, pursue the subject.

INSTITUTION OF CIVIL ENGINEERS.

June 28, 1842.

"Description of the mode adopted for sinking a Well, at Messrs. Truman, Hanbury, Buxton, and Co.'s Brewery." By Robert Davison, M. Inst. C. E.

The

The author commences this communication, by stating that one of the principal objects of the brewers, is to obtain a constant supply of water at a low temperature, for the purpose of cooling the worts, particularly during the summer months. quantity of water to be obtained from the land-springs has (he says) been represented as not to be depended upon; this would probably be correct, if required, as frequently proposed, for the supply of all the wants of a city, but if a well is properly sunk, there can be no doubt of obtaining a supply of 80 to 100 gallons per minute.

With regard to the quantity of water obtainable from the chalk stratum, the author believes it to be more precarious, for while instances occur occasionally, where a considerable opening is found in the chalk and a plentiful supply is obtained; the cases it is believed are as frequent where fissures are not met with and a failure ensues.

He then proceeds to give a narrative of the facts which occurred during the progress of an attempt to sink a cast-iron cylinder from the surface down to the chalk, a depth of about 200 feet, intending to admit the springs at the different levels, as might be considered most advisable.

The well was commenced in the middle of a landspring well 16 feet diameter, and in order to avoid the usual inconveniences of pumping and excavating, Mr. Clark of Tottenham performed a large part of the work with the "miser" instead of by the usual methods of well-sinking.

The landspring well was drained January 25, 1839, and the excavation of a well 11 feet diameter was commenced; this was carried down of a clear diameter of 8 feet 6 in. inside the brick steining, and when it had arrived at the depth of 115 feet 3 inches, the first cast-iron cylinder was lowered, and others were gradually added, shutting out the springs as they were passed, until April 3, when, at the depth of 135 feet, in a bed of yellow clay and pebbles, the water overpowered the excavators, and after trying many methods of continuing the excavation,

the use of the "miser" was resorted to, when the cylinders had gone down to 144 feet. On the 11th of May the oyster bed was reached, at 163 feet depth; and after some deliberation, it was resolved to continue sinking down to the chalk. For seven days the men were employed in "jumping" a heavy chisel bar to break through the hard rocky crust of this oyster bed; at length between the 25th and the 27th of May the cylinders suddenly sunk 5 feet 6 inches; the misering was continued until the depth of 189 feet ten inches was attained, and the cylinders were found to be completely fixed. A pressure of nearly 100 tons applied by powerful screws was tried without producing any effect; it was therefore determined to fill all the space between the steining and the exterior of the cylinder with concrete, although a portion of the steining was discovered to have given way; it was supposed that the cylinders would have been held up by the pressure against the steining and the earth; the pump-work was therefore fixed, and after a time the pumping commenced; on the 21st October, after no more than the usual pumping (the water generally containing sandy sediment), it was observed that the pavement around the well had given way; the machinery was stopped, and immediately there occurred a rumbling noise within the cylinders which lasted probably 4 or 5 minutes; on examination, it was found that the cylinders had sunk 4 inches, the main girders across the top were broken, and on sounding the well it was discovered that an extensive "blow" of sand had taken place, and filled the bottom of the well for nearly 28 feet; this was cleared out by misering, and after recommencing pumping for some time, on the 14th December a separation of the cylinders about 2 inches wide was discovered at about 73 feet from the surface. Mr. J. Braithwaite and Mr. J. Simpson were consulted as to the best method of proceeding; the former was of opinion that there was such a subsidence behind the cylinders, as would endanger the safety of the surrounding buildings. The latter did not take so serious a view of the matter; but he suggested the sinking of an internal cylinder, if the original one could not be forced down.

After this examination, a portion of one of the cylinders was cut away at 72 feet from the surface, where the soft part of the clay commenced, and a dome 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 four 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 withinside. 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 44447., to which must be added the expense of a 12-horse steam-engine and pumps 13517., making a total cost of 57957.

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.

3. The modes of Irrigation in use in Northern Italy; of Drainage adopted in the Lowlands of the United Kingdom, or works of a similar nature in Holland, or in other countries.

4. On any of the principal Rivers of the United Kingdom, (the Shannon,) or of Foreign Countries, (the Po, Italy,) describing their physical characteristics, and the engi neering works upon them.

5. An account of the waste or increase of the Land on any part of the coast of Great Britain, the nature of the Soil, the direction of the Tides, Currents, Rivers, Estuaries, &c., with the means adopted for retarding or preventing the waste of the land.

6. The various kinds of Limes and Cements employed in Engineering Works.

7. The best and most economical mode of raising large Stones or Rocks from the beds of Rivers or Harbours.

8. The conveyance of Fluids in Pipes, under pressure, and the circumstances which usually affect the velocity of their currents.

9. The means of rendering large supplies of Water available for the purpose of extinguishing Fires, and the best application of manual power to the working of Fire Engines.

10. The most advantageous method of employing the power of a Stream of Water, where the height of the fall is greater than can be applied to Water Wheels of the usual construction.

11. The construction of large Chimneys, as affecting their draught; with examples and drawings.

12. On the ventilation of Coal Pits or Mines in Great Britain, or in Foreign Coun tries.

13. The relative merits of Granite and Wood Pavements and Macadamized Roads, derived from actual experience.

14. The smelting and manufacture of Copper.

15. The smelting and manufacture of Iron, either with Hot or Cold Blast, in Great Britain or in Foreign Countries.

16. The comparative advantages of Iron and Wood, or of both materials combined, as employed in the construction of Steam Vessels; with drawings and descriptions.

17. The sizes of Steam Vessels of all classes, whether River or Sea-going, in comparison with their Engine Power: giving the principal dimensions of the Engines and Vessels, draught of water, tonnage, speed, consumption of fuel, &c.

18. The various mechanism for propelling Vessels, in actual or past use.

19. The description of any Meter in practical use for accurately registering the quar