entrance of the water into the mill-wheel, is to the sum of the apertures of egress.:

Whence it follows, by multiplying this force and this velocity, that the effect produced by the machine in a given time, is equal to the weight of all the water that the reservoir can furnish during this time, by the heighth of the level of the water in the reservoir; now this product, it is well known, is the utmost that can be obtained from the best hydraulic machines.

Finally, M. Mannoury modifies his constructions according to circumstances. He invented the substitution of a wheel with a vertical axle, instead of the one before described to be entirely immersed in the water. This wheel, which is of copper, is three feet in diameter; its circumference is furnished with forty paddles or float boards, of nearly one foot by three inches, very thin, and apart from each other about half an inch. These paddles are all inclined in the same direction on the circumference, and form a sort of circular venetian blind, in the middle of which is a space where the water is introduced from underneath by a large tube or canal. This wheel, by turning in the water in which it is immersed, meets with no sensible resistance, and answers the purpose as well as the one before described. It is imagined that the water, after having struck upon, or rather pressed only the paddles placed obliquely on the circumference, flies through the small intervals that are left between them.

The advantages of the mills invented by M. Mannoury would furnish us with subject for much interesting detail, into which we cannot enter; we shall confine ourselves to what has appeared to us to be most worthy of remark.

We have said, that he introduces the water into his wheel from underneath, which gives him the facility of

placing

placing his machinery at the side of the reservoir, and to avoid connection by toothed wheels; but this disposition has besides another considerable advantage, which is, that the column of water which enters thus into the wheel, by pressing from below on the part above, with all the weight of the reservoir, sustains a great part of the weight of the machine, and consequently greatly diminishes the friction of the pivot against the socket in which it turns; while on the contrary, when the water enters at the top, as in the old re-acting machines, which is already very heavy of itself, this flowing water con siderably augments the weight, and consequently the resistance. We are nevertheless sensible that this dispo sition cannot take place, except where the bulk of water is not very considerable.

2. It may be asked how M. Mannoury can cause the water to enter the wheel which turns, while the conduit which brings the water is immoveable. We apprehend that he can accomplish this object, by causing the pipe that brings the water to enter the collar of the wheel, so as to leave very little play between them, and also by furnishing this small interval with a leather collar; but M. Mannoury has found a more ingenious method, by furnishing the tube at bottom which is fixed, and the moveable collar of the wheel, with several cylindrical and concentrical surfaces which fit one into the other without touching. The water fills the deep and close grooves formed by the cylindrical surfaces, and is sufficient to prevent that which is forced into the wheel from escaping by the sides.

3. One of the operations most difficult to the miller, is to place and maintain his running stone upon its axis, so that it shall turn perfectly horizontal. The least shock deranges it, and then it rubs against the other stone, or Ccc 2

it

it is too tight on one side, while the other is too loose, which makes one part of the grain. too fine, and the other too coarse. M. Mannoury has found a simple and expeditious method of giving immediately to the stone its proper situation, by rendering the piece of iron which terminates the axis of this stone, a little convex at the upper part. Hence the equilibrium of the mill-stone on this axis becomes steady, so that it takes of itself the proper position, and if it happen to be a little deranged, it naturally regains its former situation.

4. The author has discovered by multiplied experiments, that the fixed stone should be perfectly flat, instead of being dressed somewhat conically as is customary.

We can suppose indeeed that when the fixed stone is dressed conically, if the running stone happens to be ever so little out of its level, the interval between the two stones becomes very irregular, and the grinding is ill performed as for the running stone, experience proves that it must retain its common form, which is that of a hollow cone, but which is hardly perceptible.

5. The learned Belidor had affirmed in his hydraulic architecture, that to succeed best in the grinding, the furniture of the running stone should be very elastic, because he thought the trembling motion of this stone served to assist in crushing the grain; but it appears certain, from the experiments of M. Mannoury, that this motion is, on the contrary, very injurious; the firmer the pivot of the axis is fixed, the better is the grinding performed; in this case, the stone becomes in some degree sonorous, and the sort of humming noise that it makes, informs the miller that it is in the most favourable position.

6. Belidor

6. Belidor had also affirmed that the heavier the running stone is, the more considerable is its effect. M. Mannoury, on the contrary, has found that light stones produce the most effect, but only until they are heated; that then they produce less effect than the heaviest stones, because the latter heat more slowly; this is expressed by the millers when they say that the mill is tired and wants rest, that is, it must have time to cool.

7. M. Mannoury made in the presence of the commissioners, a course of experiments, to ascertain the effect of the re-acting machines that he employs in his mills. These experiments offer a series of facts, verý useful to be known in practice. We have particularly remarked an ingenious expedient employed by the inventor, in order to render uniform the action of a variable power, such as the power of a man applied to a windlass, who is not always capable of employing the same degree of force and swiftness.

All these particulars are valuable, because they are the result of experiments made upon the principle of profiting by every little circumstance, without blindly following the common routine established by custom.

We think that the mills of M. Mannoury exhibit a happy application of the re-acting power of water, which for their simplicity and useful effects, merit to be often employed instead of the common mills, and that his researches are worthy of the approbation of the class.

List of Patents for Inventions, &e.

(Continued from Page 320.)

JAMES PENNY, of Low Nibthwaite, in the parish of Colton, in the county of Lancaster, Mechanic; and JoSEPH KENDALL, of Cockenstall, in the parish of Ulveston, in the said county, Turner; for an entirely new and improved principle or plan for the making of pill and other small boxes. Dated September 8, 1814.

WILLIAM LISTER, of Paddington, in the county of Middlesex, Esquire; for certain further improvements on an engine or machine for separating corn or seeds from the straw and chaff. Dated Sept. 27, 1814.

JOSEPH TAYLOR and PETER TAYLOR, of Manchester, in the county of Lancaster, Machine Makers; for having invented and brought to perfection certain improvements in a loom to be used in weaving cotton, linen, worsted, silk, or other cloth or cloths, made of any two or more of the said materials. Dated Sept. 21, 1814.

W. E. SHEFFIELD, of the Polygon, Somers'-town, în the county of Middlesex, Gentleman; for divers improvements in the working or manufacturing copper, and its compounds and other metallic substances, or any or either of the same. Dated Sept. 21, 1814.

JAMES DOBBS, of Birmingham, in the county of Warwick, Gentleman; for his improvements in the manufacturing of machines used for cutting and gathering in grain and produce arising from the earth, whereby much labour and expense are saved. Dated Sept. 21,

1814.

AMBROISE FIRMIN DIDOT, of Holborn, London, Gentleman; for an improvement in the method of mak