begin to rain they soon cease to rise; but other columns spring up contiguous to them, generally on the S. W. side of them, as far as I have observed, and as theory seems to indicate, and go through the same process of cap-forming, hazing and raining as the parent cloud.

These new columns when they first make their appearance I have denominated sprouts. This name is not inappropriate, for these sprouts are evidently generated, or at least assisted in their growth, by the parent column, in the following manner. As the parent column rises into the upper current of air, which generally comes from the S. W. or W. S. W. its top is made to lean towards the N. E. or E. N. E., but by its inertia it causes the current there to run a little slower, and so the column which may be about to form behind it towards the S. W. finds less difficulty in rising, and preserves a more erect position, and thus can attain a greater elevation. Hence, the first attempts of columnar clouds to rain are generally failures, because their tops are generally shaved off or pressed over towards the N. E., and thus dissipated without raining: each succeeding cloud in its wake finding a stiller air in its upward motion attains a greater elevation. Finally, one reaches a height sufficient to produce rain, and then a new source of power is called into action, powerfully aiding the formation of sprouts. This is the descending rain cooling the air below the cloud, and causing it by its greater specific gravity, and also by the weight of the drops of rain, to move outwards in all directions from the centre of the rain.

Now as the air all round the parent cloud is running in at the base of the cloud and below towards the cloud, this air is obliged to rise up over the stratum of cold heavy air, pressed outwards around the borders of the shower, and thus its upward motion is increased; and as the dew-point is more likely to be higher on the south side of the cloud than on the north, sprouts will on that account be more likely to form on the south than on the north. To see the formation of sprouts to the greatest advantage then, the cloud should be to the north of the observer.

If these theoretical deductions are correct, and as far as observation extends it does not contradict them, it would follow, that the progress of rain may be from a northern direction, though the upper current may be constantly carrying the hazy cloud formed from the tops of all these columns towards the east. Further observations are wanting on this point.

I would recommend that gentlemen residing in mountainous districts, where the clouds sometimes form on the sides of the mountains, should ascertain the perpendicular height of these clouds at their base, and see whether they are one hundred yards high for every degree of Fahr, which the temperature of the air is above the dew-point at the moment of their formation.

If gentlemen have no means of taking the dew-point directly, the following method will be found equally correct in ascertaining the height of the base of these particular clouds, at any time of the day, for the height varies every hour. Swing a thermometer (Fahr.) rapidly in the air to avoid the effect of radiation, note its temperature, then cover its bulb with a wet rag and swing it as before until it sinks as low as evaporation can make it, then divide one hundred and three times the difference of these temperatures by the wet bulb temperature, the quotient will be the height of the base of the clouds in question, in hundred yards. For example, suppose the dry bulb is 56° and the wet one 514°, then the base of the clouds will be 1000 yards high. This height is calculated on the supposition that air cools at 4° Fahr. in

ascending to a height where the barometer would be one inch lower than at the surface of the earth, and 4° more for every additional inch. If this latter law is not strictly correct, the height of the base of the cloud in question will vary accordingly, and the law itself may be accurately inves tigated by this method, for the precise degree of refrigeration necessary to condense vapour at a particular dew-point is known, after making an allow ance for the expansion of the vapour itself and the fall of the dew-point on this account. As the discovery of a method to ascertain by the thermome ter, the height of a particular kind of cloud easily distinguishable from all others, is a matter highly curious in itself, independent of its connexion with the theory here advocated, it will no doubt receive that immediate attention which it deserves.

Franklin Institute.

COMMITTEE ON SCIENCE AND THE ARTS.

Report of Committee to try experiments with Spark Arresters. The Committee on Science and the Arts, constituted by the Franklin Institute of the State of Pennsylvania for the promotion of the Mechanic Arts, to whom was referred for examination, by experiments, the apparatus for stopping the sparks from issuing from the flues of Locomotive Engines, submitted in competition for the premium offered on behalf of the Newcastle and Frenchtown Turnpike and Rail Road Company, REPORT:

That, from the plans submitted in competition for the offered reward, they selected three of the most promising, which they recommended the respective inventors to put in order for trial; at the same time they inform ed the other competitors that theirs also would be tried, if they requested it. Through the liberality and kindness of the Beaver Meadow Rail Road Company, and the Philadelphia and Trenton Rail Road Company, the Committee have been favored with the use of the engine of the former, and of the road of the latter for making their experiments. One of the plans selected having been withdrawn, and none of the others claiming the privi lege of a trial, there remained but two to be subjected to a practical test, viz: one invented by Jas. P. Espy, Esq. and the other by Mr. S. Gerhard. The one by Mr. Gerhard, consists of a series of revolving fan wheels placed horizontally one above the other near the top of the chimney or smoke pipe, the wheels or fans were placed nearly in contact one above the other, having just sufficient space to admit of motion independently of each other, and the twist of the fans reversed in the middle one, so that its revolution should be in the opposite direction from the other two. The revolving motion to be produced after the manner of a smoke jack, by the current of air and steam passing up the chimney.

This apparatus was first put upon the engine and the fire attempted to be made, but it was found that owing to the too small capacity of the passage through the fans, the firing was difficult and tedious, and that it was impossible to keep up the steam for a moderate velocity of the engine and tender. The effect in arresting the fire sparks was rather unexpected, as not a single spark was seen to make its escape, although care was taken to use such fuel as would furnish them in the greatest profusion. This result could only be ascribed to one of the three following causes, either the ope

T

ration of the fans had been effectual in beating back and destroying the sparks, or as the engineer who accompanied the Committee supposed, the obstruction to the draft being great the steam was necessarily so damp as to extinguish them, (and being in the night time they were invisible,) or what was considered highly probable, the obstruction was so great as to prevent the creation of an upward current sufficiently powerful to raise the sparks to the top of the chimney, and that any other obstruction operating in the same degree, would be attended with the same results. Accordingly, at a subsequent trial, a piece of sheet iron eight inches wide was secured across the top of the smoke pipe leaving an opening on each side three and a half inches wide, with the intention of making about the same amount of obstruction as had been caused by the before mentioned fans. The result of the experiment was nearly similar. The obstruction in the latter case was evidently, from other indications, not quite so great as in the former, and a very small number of sparks occasionally made their appearance. Whilst the committee acknowledge that their experiments go no farther than to show that the favorable results obtained by the inventor, previously to his submitting it to the examination of the Committee, and that obtained by the Committee as above mentioned, may have been owing rather to its efficacy as a draught obstructor, than to any good principle of action as a spark arrester, they can see no good reason for advising the inventor to incur the further expense of constructing one of larger dimensions, being persuaded that one of sufficient capacity to allow a free passage of the smoke and escape steam, would be attended with little or no impediment to the sparks. The apparatus, called a draft-increasing chimney cap, invented by J. P. Espy, Esq., is of sheet iron, in the form of a cone, and is placed upon the top of the smoke pipe, with its axis horizontal and its lower side pierced about midway to receive the upper end of the pipe. The base is open with the exception of a wire-gauze covering, which is intended to retain the sparks within the cap. It is intended to turn upon a swivel and be governed by a vane, so as always to present the apex of the cone towards the wind; the intention of which arrangement is to create a partial vacuum at the base of, and within the cone, to compensate for the obstruction consequent upon the use of the wire-gauze. The Committee upon trial, found that this apparatus did produce the effect of increasing the draught to some extent, but although the gauze used was of the finest kind in use, No. 19, or 19 meshes per inch, yet the sparks found their way through in sufficient quantity to be troublesome. How far the draft-increasing property of this cap may operate, to compensate for the resistance of the gauze, when that shall be of sufficient fineness to effectually prevent the escape of sparks, the Committee have not the means of judging with any degree of precision, but they incline to the opinion that the compensation would not be complete without such an arrangement as would render the apparatus inconvenient if not unmanageable, particularly on roads which require the pipe to be dropped for passing under bridges. An objection arises from the circumstance of the sparks, dirt and water, when any such escape, being thrown backward, and consequently more likely to incommode the engineers, than when discharged from the top upward, and all around the sides. There seems, likewise, a want of some means of disposal of the sparks arrested, as they are necessarily retained against the gauze until they become so much reduced by combustion as to be forced through it, and likewise of a trap or valve to remain open when the draught is not urged by the exhaust steam. Upon the whole, the Committee are of the opinion that this arrester

does not come within the terms and conditions of the offered premium, and though they confess, that the trials have not been sufficiently numerous and diversified to enable them to speak with certainty as to its comparative merits, yet they feel constrained to say, that they do not perceive how the objections already alluded to, can be so far removed as to bring it into competition with one or two which have been since invented.

The thanks of the Committee are due to Messrs. Garrett and Eastwick, for their kindness in keeping the locomotive, at their own risk, for the accommodation of the Committee.

By order of the committee. August 11, 1836.

WILLIAM HAMILTON, Actuary.

Mechanics' Register.

AMERICAN PATENTS.

LIST OF AMERICAN PATENTS WHICH ISSUED IN FEBRUARY, 1836.
With Remarks and Exemplifications by the Editor.

(CONTINUED FROM p. 195.)

59. For Sawing with a Band Saw; William Carey, Poughkeepsie, Dutchess county, New York, February 17.

The patentee claims as his invention, "the band saw running on two wheels, and the arrangement of the machine in which it is to operate." For the validity of which claim, see our remarks upon the patent of Benj. Barker, p. 112 of the present volume; every remark respecting which applies fully to the present patent.

60. For Cannon for firing chain shot; Edward Gordon, Hingham, Plymouth county, Massachusetts, February 17.

A double barrelled cannon is to be made, one vent discharging each. A ball is be put into each gun, the two being connected by a chain of suffi cient length to admit of this. The guns are to diverge a little, in order to stretch the chain before the balls reach their intended object. There is not any claim made, but the patentee descants on the use of his invention, and the destructive effects of balls so connected, as though chain shot had never been used. Now it certainly behooves a man, before he attempts to improve a system of any kind, to acquire some knowledge of what has been previously done, for, when science and interest have long been combined in order to obtain the best results, it rarely happens that an indifferent person will stumble upon any great improvement, all vulgar adages to the contrary notwithstanding.

We do not know that chain shot have been fired from double barrelled cannon, nor do we believe that they ever will. We offer the following opposite quotaion from "L'Allemand's Artillery." "The Annals of Paris and Vienna alone, are crowded with contrivances, all curious in their way, but offering models that do more credit to the imagination than to the judg ment of their authors. Among a thousand inventions, or fancied improve ments, it is difficult to find a single one that has not already been made and

condemned; and even if it be new, it cannot be admitted into a system until it has been submitted to practice during the course of a war."

61. For a Machine for hulling Clover Seed; John B. and William F. Poague, Lexington, Rockbridge county, Virginia, February 17.

A conical stone is to revolve is a corresponding hollow cone of the same material. The mode of fixing, driving, &c., are all quite antique; and the claim is to the "before described machine;" which claim may be perfectly correct, if by the before described machine, we are to understand a machine which has been repeatedly before described.

62. For a mode of fastening Mail Bags, &c.; Ira Atkins, Hanover, Grafton county, New Hampshire, February 17.

There is to be a lock, with a bolt, shot forward by a key in the usual way, but to the end of the bolt is to be hinged a flat plate of iron, which is one of a series hinged to each other, and forming a chain, or flat strap, each plate has a tongue on it which is to shoot into a staple; a row of such staples being fixed on one side of the bag, and passing through openings on the other side. The claim is to the whole arrangement, with the exception of the ordinary lock bolt. The contrivance appears to us to be one which will be more troublesome than useful.

63. For a Mortice door latch; William Coover, Erie, Erie county, Pennsylvania, February 12.

This mortice latch, or bolt, presents no feature of novelty, nor is any part of it claimed. It consists merely of a bolt with a zigzag spring behind it; the bolt being contained in a suitable case, and having a tumbler, and handle, by which it is to be acted upon.

64. For a Spark Extinguisher; Abraham McDonough, City of Philadelphia, Pennsylvania, February 17.

In this spark extinguisher there is to be a lining of sponge within the cap which constitutes the upper part of the chimney, and this lining is to be kept wet by the percolation of water through small tubes in the bottom of the trough, which is fixed at the upper edge of the cap; there is to be a water trough also at the lower end of the cap, into which sparks are to fall. The description and drawing, although not models of clearness, may suffice to enable a shrewd workman to construct the apparatus, but there is not any thing to guide us to a knowledge of what is claimed; it cannot be the use of water, and the lining of the cap, as these are not new, and this lining and upper trough may, according to the patentee, be omitted. We are apprehensive, however, that amending the specification would not remove the main difficulty, as it will not enable the machine to attain the proposed end, which we very much doubt its ability to do.

65. For an improvement in the manner of raising and depressing the steam and exhaust valves of Steam Engines; William Duff and Thomas Murphey, City of Baltimore, Maryland, February 17.

The object of this arrangement appears to be to operate upon the induction and eduction puppet valves by rods acting in a direct line. Th claims are, "First, the arrangement of the valve-stem in the top-chest, an inverted position, so as to be connected by means of the rod with th