Of constructing Blowing-Machines, with Falls of Water of great

height.

Where the height of the fall is great, the quantity of water is usually small; and in all the ways of application that have hitherto been contrived, the height will by no means make amends for the deficiency in quantity.

In the common construction of these machines, where the upper pipe, or funnel, is no more than three, four, or five feet high; though the fall should be such as to admit of the lower pipe being thirty or forty feet or more, it does not appear that any material advantages could result from such a height. For, as the air is admitted into the water only at the top of this long pipe, it cannot, I think, be supposed that the quantity admitted will be the greater for the length of the passage under the place of its admission. Water indeed has been found by Marriotte to run faster through an upright long pipe than through a short one: a quantity of water which was forty-five seconds in running through a pipe three feet long, was discharged in thirty-seven seconds, or near a sixth part less time, through a pipe of the same bore, and a double length; so that, as more water passes successively through a long pipe than through a short one, in equal times, more air also must be carried down by it. But in the case which we are here considering, no benefit can be expected on this principle; for as the supply of water is supposed to be limited, the bore of the pipe must necessarily be made less, in proportion to the increase which its length may produce in the velocity. If the lower pipe is of such a height that the watery column it contains may sufficiently resist the force of the air in the air-vessel, it should seem that any further addition to its height could be of no manner of use. We have seen, in the foregoing part of this essay, that it would be more adviseable in such cases to shorten the lower pipe, and to lengthen the upper one: by this means the water, acquiring greater velocity at the place of its discharge from the upper pipe into the lower, is enabled to divide or spread more, and thus to receive more air into its interstices. The advantage thus obtained does not, however, increase in so great a proportion as the height does. From an experiment above related, it appears, that by increasing the height four-fold, the effect was not increased three-fold; and this even in small heights, where the effect is much more influenced by a variation in height than it is in great ones.

The observations already mentioned, point out the means of availing ourselves more advantageously of high falls, so as to produce always, with certainty, from a fall of a double or treble height, a double or treble effect, if the quantity of water be the same; or an equal effect, with one-half, or one-third, the quantity of water.

Experiments have convinced me that a fall of fourteen feet is more than sufficient for compressing the air to such a degree as to be able to sustain the gauge to the height of four feet; or to raise, on an opening of a square inch, a weight of about a pound and three-quarters avoirdupois, or above two pounds troy; a compressure which is

apprehended to be as great as there will in general be occasion for. Where we have plenty of water with such a fall, we can drive in air, with this force, in any quantity: for if one machine, with a certain portion of the stream, produces a continued blast of this strength, through a pipe of a certain bore, as an inch, or three-quarters of an inch, it is evident that the quantity of air may be doubled, trebled, &c. at pleasure, without diminishing the compressure or force of the blast, by adding another and another machine, till all the stream is employed. It is plain, in like manner, that the same advantage may be received from high falls, by placing one machine over another; that after the water has performed its office in falling through one machine, it is still capable of exerting the same action in another and another machine, so long as equal spaces remain for it to fall through; so that the total effect must be the same as if a quantity of water, sufficient for working all the machines, came at first in one

stream.

A natural fall of water of twentyeight feet, formed into two artificial ones of eighteen feet each, is represented in Fig. 1. This double machine may be presumed to have twice the effect of a single one, in virtue of this division; besides the advantage of the more free admission of air, and the spreading of the stream through a pipe of a much larger bore, by which it is enabled to carry down in its interstices a much greater quantity of air. The two vertical lines in the upper reservoir represent a cylindrical grating of iron wire, to keep back weeds, &c. The division of the air-vessel, and the course of the water from the upper machine to the lower, are apparent from the figure.

Fig. 1.

In the lower machine, whose air-vessel is sunk to a considerable depth in a pit made in the ground, the water is forced up in the pit, on the outside of the vessel, four feet higher than the surface of the water within the vessel, or of the stone on which the water dashes, called by the workmen the dash-board. The air-vessel of the upper machine having an additional part at one side, which performs the same office as the pit, the water is in like manner forced up to the same height in this outer part; which outer part serving as a reservoir for the machine under it, the water begins to act in this lower machine four feet higher up than the dash-board of the first. Whatever number of machines the fall will admit of, VOL. VI.-No. 5.-NOVEMBER, 1828.

42

the case is the same in them all: though in each of them the water falls eighteen feet, yet as it is pressed up again four feet for the succeeding machine, one machine takes up but fourteen of the real fall.

Fig. 2.

The outer vessel, and its communication with the air-vessel, may be conveniently formed by an upright partition in the air-vessel itself not reaching quite to the bottom. The outer division may be open at top, and need not be so high as the close air-vessel; it is fully sufficient if it reaches a little more than four feet above the level of the dash-board, the water which it is designed to receive not rising higher than this. In other respects, the structure of these machines agrees entirely with that of the single ones already described. It must be observed only, that the colanders of the lower machines should be, as nearly as possible, of the same dimensions with those of the upper ones. For if they are of smaller bores, they will not admit of all the water which passes through the upper ones, so that part of it must run to waste; if they are larger, the water will pass off too fast, without producing its due effect. The regulators before described are here particularly useful, affording ready means of increasing or diminishing the apertures in the colanders occasionally while the machines are at work.

Fig. 2 is a prospective view of the colander, screwed to the upper pipe, drawn to a larger scale, to show the disposition of the holes. The holes may be made wider than formerly proposed, as an inch each side, to prevent any danger of their being choked up.

A

Of Blowing Machines, with low falls of Water.

The dimensions hitherto given are such as appear the most advantageous. Much lower falls, however, than those which the foregoing machines are calculated for, as ten, eight, or perhaps seven feet, may be made to afford a strong blast. To produce such a compressure of the air in the air-vessel, as to raise the gauge four feet, a fall of about six feet is necessary for the lower pipe. If the upper pipe is only about a foot and a half or two feet, the water, when divided by means of the colander, will carry down a certain quantity of air; and though the quantity, from an equal stream of water, will not be so great as when the fall is higher, yet, as there are in many parts of the kingdom large bodies of water running with such a descent, the deficiency may be compensated, as already noticed, by enlarging or multiplying the machines.

For many purposes, still less falls will suffice. The smith's bellows, as we have formerly seen, raises the gauge only about fourteen inches; and such a compressure, it is presumed, may be gained from a fall of five feet or less. Small falls may be applied also to another purpose, of no little importance, the ventilation of mines and coalpits, or the driving in of fresh air, in the room of that which the mineral vapours have rendered unwholesome or pernicious.

In all these machines, it must be observed, that the height of the column of water falling through the pipe, determines not the actual force of the blast, but the greatest force which can be given it in that machine: that the height of the gauge is always the measure of the. actual force; that this force depends on the width of the pipe through which the air is discharged from the air-vessel, and may be diminished or increased in any degree up to the greatest that the column of water can resist, by widening or narrowing the aperture of the pipe; that different machines will give blasts of equal force through pipes of greater or less width, according to the greater or lesser quantities of air which the water carries down with it; and that, therefore, the size of the blast-pipe must be adjusted by trial, for each particular machine.

The distance of the dash-board under the pipe may likewise admit of some variation, and require to be regulated according to the size of the pipe. In some of the common machines this distance is three or four feet, or more; but so large a space is apparently a disadvantage; for so much of it as is more than sufficient for the free passing off the water is entirely useless, being, in effect, so much taken off from the height of the fall. The distance of six inches, laid down in the foregoing machines, is designed for a circular pipe of twelve inches diameter; in which case the area, by which the water is discharged all round, is just double to the area of the pipe, and consequently more than large enough for letting the water off without impediment.

AMERICAN PATENTS.

NUMEROUS applications are made at the Patent Office for information respecting the mode of taking out patents, and the tenure by which they are held; to answer these inquiries the subjoined directions have been drawn up, and printed for distribution. The points which have been noticed, are those to which these inquiries ordinarily relate; and it will be seen by those who have been attentive readers of this Journal, that for much of the information given, the editor is indebted to the essays on the patent laws, written by his friend P. A. Browne, Esq.; it is indeed from an attentive study of these excellent essays, that he has derived a large portion of the knowledge which he possesses of the actual operation of the patent laws of this country, and of England.

Information to Persons applying for Patents, or transacting other business at the Patent Office.

DEPARTMENT OF STATE-PATENt Office.

The Acts of Congress which relate particularly to the granting of Patents for inventions and improvements, are two in number; the first was passed February 21st, 1793; and the second, on the 17th of April, 1800.

The persons who have a right to take out patents, are all citizens of the United States; and aliens who have resided therein for two years. In other cases they can be obtained only by a special act of the national legislature.

Joint inventors may take out a joint patent, and where two or more persons have concurred in perfecting any invention or discovery, it would seem necessary that they should also concur in taking out a patent, as neither of them can justly claim to be the sole inventor.

In case of the decease of an inventor, who has not taken out a patent for his invention, it may be obtained by "the legal representatives of such person, in trust for the heirs at law of the deceased, in case he shall have died intestate; but if otherwise, then in trust for his devisees." "And when application for a patent shall be made by such legal representatives, the oath, or affirmation," &c. "shall be so varied as to be applicable to them." (Act of 1800, sec. 2.)

The term for which a patent is granted, is fourteen years: a patent cannot be renewed at the expiration of this term, excepting by a special act of Congress.

The things for which a patent may be obtained, are, “any new and useful art, machine, manufacture, or composition of matter, or any new and useful improvement on any art, machine, manufacture, or composition of matter, not known or used before the application." (Act of 1793, sec. 1.)

The thing patented must be new. "Every inventor before he can receive a patent, shall swear, or affirm, that he does verily believe that he is the true inventor, or discoverer of the art, machine, or improvement, for which he solicits a patent." (Act of 1793, sec. 3.) In the case of a resident alien, it is required, that he declare on oath, or affirmation, in addition to what is required from a citizen," that the same hath not, to the best of his or her knowledge or belief, been known or used in this or in any foreign country." (Act of 1800, sec. 1.) It thus appears that an alien is restricted from taking out a patent although he may be "the true and original inventor or discoverer," provided the thing has "been known, or used, in this or any foreign country."

ON THE FORMS, AND MANNER OF PROCEDURE, NECESSARY IN APPLYING FOR A PATENT.'

The method of applying for a patent is by petition, addressed to the Secretary of State, which is usually in the following form: