amounted to proof of the instrument's accuracy for, it seemed to him that Mr. Wicksteed had omitted to take into account one important item of force, without the exertion of which, a piston could not be brought from a state of rest into a state of motion. He referred to the force required to give velocity to the piston. Mr. Wicksteed had weighed the greater part of that resistance which might be called ponderable, and had estimated the remainder, assigning about 12 lbs. per square inch on the piston as the total amount, after deducting the resistance to the piston's descent arising from uncondensed steam. Thus, an elastic force of 12 lbs. on the piston would counterpoise a resistance of 12 lbs., but the motion would not ensue until a superior force were applied. Considering the number of strokes made by this engine per minute, Mr. Parkes could not estimate the velocity of the piston at less than from 300 to 400 feet per minute, which was very great for this enormous mass, and would require the exertion of proportionate power. He regarded the piston of the engine loaded with 12 lbs. per square inch, as he would a ball of 12 lbs. weight in a gun balanced by a fluid of a corresponding elastic force; but such ball would remain motionless unless it were propelled by some additional force. This state of things had been denominated by Professor Barlow "the preparation for motion." Now as Mr. Wicksteed's estimate proceeded no further than the production of this state of things, and as Professor Moseley's Constant Indicator recorded the mean pressure of the steam in the cylinder as barely equal to it, he could not assent to the accuracy of either method of determining the total resistance overcome by the steam.

Mr. Parkes would cite the experience of others as to the quantity of force actually expended in giving velocity in a Cornish engine, over and above that necessary to balance the weight at the opposite end of the beam, friction, &c., included. In the fifth part of vol. iii. Trans. Inst. C. E., Mr. Enys has reported some experiments made at Mr. Parkes' suggestion, on several engines. He would cite those of the Tresavean, as the cylinder was of the same diameter as the one at Old Ford, viz., 85 inches. The water load was equivalent to 12lbs. per square inch on the steam piston, and when about half the usual velocity was given to the piston in the in-door stroke, a pressure of about 17 lbs. was denoted throughout the stroke, by a mercurial column connected with the cylinder. Mr. Loam had since transmitted to him the following abstract of experiments made on the same engine, January 28, 1842. "Two indicators were used

at the same time, and an open mercurial gauge. The engine was held in-doors until the mercury became stationary, in order to ascertain the minimum quantity of steam power necessary to produce motion. The pressure was 15lbs. per square inch, when the water load was 12lbs."

Here, then, a force of 3lbs. was found requisite to establish an equilibrium between the power and resistance; and a further force of 24lbs. per square inch was necessary in order to urge the mass at about the half of its ordinary velocity. Mr. Enys stated that less pressure was exhibited when the engine was brought in slower, and vice versá; and this was consistent with every-day experience.

Now though the Old Ford engine had not to overcome so much frictional resistance as a deep mine engine, yet, having a weight to raise, according to Mr. Wicksteed, alone equal to 11.8lbs. per square inch on the piston, Mr. Parkes was of opinion that this could not be effected at the usual working velocity, with less than 14 or 15lbs. pressure of steam per square inch. He would suggest to Mr. Wicksteed, to repeat Messrs. Enys and Loam's experiments, and also to work his engine with steam reduced nearly to such pressure in the boiler as would barely suffice to bring the piston down. Such experiments would confirm or invalidate the results given by Professor Moseley's instrument, and probably lead to the discovery of its imperfections, should any exist.

PURIFICATION OF THE WATER SUPPLY OF THE METROPOLIS.

SIR,-I perceive by some letters which I have lately perused in your scientific periodical, that the subject of a supply of pure water is again brought under discussion. That question has been so often brought forward, and so ably seconded by men eminent for rank and scientific knowledge, that I should not presume to address myself to you on the subject, were it not that I think it the duty of every individual to communicate his ideas, when those ideas are based on a desire to promote the comfort and health of numbers of his fellow-creatures. Many complaints of the water supplied in different houses have met my ears of late, and I really think that if Mr. Stuckey's invention can be rendered available for our great metropolis, it certainly ought to receive that attention forthwith which so excellent a plan deserves.

Much money has been expended, and

partial good has been obtained, but that is not enough when an evil can be remedied effectually. If, by means of the invention I have alluded to, the water of our noble river can be restored to its pristine purity, and delivered clear, and free from extraneous matter, to every house in London at so cheap a rate as that specified by Mr. Stuckey, it does appear to me that all the companies in London ought to adopt it immediately; and their backwardness on this occasion is only another proof of that mistaken economy which distinguishes this calculating age. They have already spent enormous sums-they expend every year costly incomes-on inefficient modes of advancing a most important object, and now they hang back, alarmed at the idea of further expense. But let them recollect that if this invention should be proved to realize all that it promises, their expenses, after the first cost would be reduced, and the object of many years of ineffectual effort gained at once.

I hope the time is not far distant when the new company which is forming will supply us with water far superior in quantity and quality, and at an infinitely cheaper rate, than what we now receive from the existing monopolies.

I have the honour to be, yours, &c.,
A CONSTANT READER.
London, July 5, 1842.

the combustion of oxygen and hydrogen, which are separately conveyed to a peculiar burner by the two conducting pipes, C and D. In this burner, which should be very thick and solid, a tubular cavity B is bored, which branches off at the bottom, and is there connected to a compression blow-pipe box F, by means of the curved tube E, and the stop-cock G. The part B is about one quarter filled with fine filings of either iron, zink, copper, antimony, tin, silver, or their respective sulphurets. The hydrogen and oxygen gases being now let on and lighted the compression box stop-cock is turned, when a gust of expanding air, or oxygen, throws up all the metal filings through the intense compound flame, and into the atmosphere burning with vivid scintillations and of the most beautiful colours imaginable. The same thing may be done, and with, I think, some trifling advantage, by reversing the apparatus, so that the flame may play downwards, and raising it a few yards from the ground. No blowing apparatus will be here necessary, the filings being merely dropt through the tube B, which should in this case be open at both ends, the uppermost one being provided with a funnel to facilitate the introduction of the various metals. I am, Sir, yours, &c.

M. J. BRAZENDALE.

THE DISC PROBLEM.

SIR,-The long-pending problem of the discs having never yet been satisfactorily explained, I will, with your leave, attempt a solution, and by so doing add one more to the list of candidates for the high honour of solving this very perplexing query.†

Having paid a good deal of attention to this curious phenomenon, I have tried the experiment in almost every variety of way, which has led me to the following conclusion:-that a current of air in rapid motion, in any direction, loses the power, to a certain extent, of lateral resistance. In proof of this, I will mention an experiment or two, and then apply it to the solution of the case in hand.

If such a thing be not easily procured, a pair of common domestic hand-bellows answers very well.

The phenomenon alluded to by our correspondent was first noticed by M. Clement Desormes, and was the subject of several papers in our 8th and 9th volumes. See particularly vol. IX., p. 283.-ED. M. M.

lap the card about a of an inch, and give the card a slight curve lengthwise, so that the tube will be on the hollow side of the card; then lay another card (loose) upon this, in such position that the end of the tube is between them; then, with the tube in your mouth, holdit in a horizontal position, blow, and whether the moveable card be above or below, it will maintain its position, so long as the blast is continued. When the moveable card is undermost, small weights may be suspended from it, as in the disc experiment; the stronger the blast, the greater the weight supported; there is this difference, however, between it and the discs, that in the latter the whole force of the blast is directed against the moveable disc, operating to its disadvantage, so that it is only the difference of power between the two that retains it in its place, whereas, in this case, having no opposing influence to contend with, it is held in its place with a greater attractive force.

I conceive the sudden fall of the barometer during a heavy gale of wind to be analogous to this, and produced by a similar cause.

We next come to the consideration of the question, Why do currents of air lose part of the power of lateral resistance ? To illustrate this, we will suppose air at a given pressure to be forced through a pipe of a certain width, at the rate of 2 feet per second. If any part of the pipe be enlarged to double the width, in that part it will only travel at the rate of one foot per second, its velocity bearing a constant proportion to the width of that part of the tube, when compared with the end at which it entered.

In the case of the discs, the air, after it leaves the tube, radiates in every direction, and as it increases in superficial area, the thickness of the rings of air, so to speak, become diminished, in proportion to their lateral expansion; otherwise the velocity of the current must be retarded, as demonstrated in the pipe experiment; hence we see the reason why the experiment succeeds best when the discs are a little concave, for by this means the capacity of the space between them is justly proportioned to the evervarying dimensions of the current. The space is thus occupied by air in rapid motion only, and under such circumstances that every particle of air preserves the full amount of velocity, or momentum, imparted to it on entering the tube; consequently, any force applied to separate them, is in opposition to that momentum, because, as we have seen in the case of the pipes, an increase of volume retards the velocity of a current, so in this case, if the distance between the discs be increased, the air on leaving the tube receives a check, and is compelled to Occupy a space greater, and assume a velocity less, than is due to it.

Once more: Lay the moveable disc on a table, and hold the disc with the tube within or of an inch of it, commence blowing, and the other disc will immediately jump up, and stand, or rather hang, at the proper distance, so that the space between them shall be occupied by the current only; the air in its passage through the tube acquires a velocity that carries it forward through the increased space, till its power is exhausted; the whole of the momentum imparted to it in the tube is consumed in an effort to draw after it the air between the discs, the movable one rising to supply its place.

By giving insertion to these remarks in your highly useful publication, you

will confer an obligation on one who con-
siders himself deeply indebted to your
work for much valuable information.
Perhaps it may be the means of drawing
the attention of scientific men once more
to this subject, for it must appear to every
one an exceedingly humiliating circum-
stance, that an experiment apparently so
simple, should remain so long in statu
quo.
I remain,

Yours, very respectfully,
WILLIAM WYNN.

Beverly, June 27, 1842.

ABSTRACTS OF SFECIFICATIONS OF ENGLISH PATENTS RECENTLY ENROlled.

JOHN GARNETT, MERCHANT, AND JOSEPH WILLIAMS, MANUFACTURING CHEMIST, BOTH OF LIVERPOOL, for an improved method of manufacturing salt from brine. Enrolment Office, May 9, 1842.

Instead of applying the heat to the bottom or sides of the pans containing the brine to be evaporated, the patentees adopt the very novel mode of passing the heat in the form of steam through the brine, by means of pipes or tubes. "What we claim is the mode of heating brine in the manufacture of salt, by applying cylindrical or curved surface pipes or tubes for conveying steam through brine." By and by we may expect to see the heat itself laid under the embargo of a patent monopoly !

JOHN EDWARDS, OF SHOREDITCH, WAREHOUSEMAN, for improvements in giving signals on railways. Petty Bag Office,

June 11, 1842.

Mr. Edwards, the patentee of these improvements, says, "I am aware that at stations on railways there are lamps used by which it is indicated to a coming train whether it is to stop or to proceed beyond a lamp; and (that) there are also surfaces used for like purposes for the day; but there is no means of making a communication to a coming or passing train, or between two trains." In this assumption Mr. Edwards is assuredly very much mistaken, as may be seen by reference to the specifications of Mr. Curtis, Mr. Hancock, and two or three other preceding patentees who might be named.* Mr. Edwards' "improve

• If Mr. Edwards had said there were no means adopted, he would have said no more than probably is true; for notwithstanding the number of good signal systems which have been lately invented, we have not heard of any of them coming into use. At the opening of the Primrose Hill Tunnel, on the Birmingham line, and at the Paddington Terminus of the Great Western, the system of Mr. C. B. Curtis, described in our No. 943, has been experimentally applied (at Mr. Curtis's own expense) for a great many months past, and acts so well as apparently to leave nothing to be desired; but that is allneither Company adopts it-they see and approve,

ments" consist first as regards night signals, in using a series of lamps or surfaces "in such manner as to obtain varied communications thereby, according to the different combinations which may be made, by closing and opening the various lamps in different orders and combinations in respect to each other ;" and secondly, as regards day signals, by the use of a series of thin plates, and by the different changes which may be obtained by turning some edgewise and presenting others to view." The reader will see, at once, that there is nothing in these so called "improvements," but what is very old and also very well known. The claim is to "the mode of using a series of lamps or surfaces, and of obtaining and giving signals or communications on railways, by the varied combinations which may be had by the changing of the relations which the lamps or surfaces bear with respect to each other."

FRANCIS MARX, Esq., of No. 81, EATON SQUARE, IN THE COUNTY OF MIDDLESEX, for certain improvements in the construction of ships or other vessels, and the methods of propelling them. Rolls Chapel Office, June 16, 1842.

These improvements consist, first, in a peculiar mode of forming the hulls of vessels; secondly, in the application thereto, or to vessels of the common construction, of submerged propelling or paddle wheels; and thirdly, in a method of connecting these submerged wheels, or any other paddle or propelling wheel, with the steam-engine and that part thereof called the waste pipe, for the purpose of facilitating the condensation of the steam.

1. "In constructing the vessel," says the patentee, "I provide a curvilinear or arched deck, which I call a shield deck, to be faced with iron, and which I form to an arch of any desirable curve, which facing shall form, with the direction of any missive discharged from cannon afloat, an angle of any desired degree, so that it may glance or throw off said missive. The said shield deck, in connexion with the hull or parts of the vessel below it, forms an air or water-tight bulk head, which may be divided into one or more compartments, and gives (by its displacement of water) a buoyancy by which said vessel will float, though said vulnerable parts of the vessel, or those parts above the line of said arch and its abutments, be pierced or torn by shot, so as to admit water. The steam-engines, machinery, and

but pointing to the prodigious number of passengers conveyed without accident, seem to ask "Whether it is worth while being at a farthing of expense for the sake of the two or three (old women or ecclesiastics') who may be occasionally smashed to pieces ?"

water-wheels, are placed below said shield deck, and every part of them below the water line, so as to be out of reach of shot; and the water-wheels being from their position submerged, are relieved from the effect of the sea.'

For the better elucidation of this branch of his improvements, the patentee gives drawings of a steam-vessel adapted for harbour defence, showing the shield deck faced with iron, and supported by wooden or metal beams, or angle iron beams. The abutments of the shield deck are directed to be joined and secured all round the vessel, "in any convenient or suitable manner, and at any required distance below the water line, so as to be out of the reach of shot." The summit of the shield deck is in a line with the line of the keel and midship, and is elevated the same distance above the water line as its abutments are below it. The hatches or hatchway is placed midship in the summit of the shield deck, and fitted with watertight metal sides, to travel or slide fore and aft on or within the shield deck. The abutments of the shield deck are in like manner below the water line, and by reason of their distance below it, out of the reach of shot; and as the surface of the shield deck is faced with iron, and may be made to present any desirable angle with the direction of any missive discharged from cannon afloat or otherwise, it is considered that "such angle will cause the said missive to be glanced or thrown off," so that that part of the vessel which is under the surface of the shield, will be effectually protected from the effect of shot.

2. The water-wheels of the vessel revolve

horizontally under water. The wheels are hollow water-tight cylinders or drums, to which paddles or floats are attached; and are placed in wheel cases or openings made in the sides of the vessel, and fitting the wheels as near as may be without being in contact. The wheels may be either fixed permanently to or made to detach at pleasure from vertical shafts passing through the floor of the vessel into the wheel cases; and in the floor a pedestal and stuffing boxes are placed, the former to support the wheel shafts in their position, and in which they also revolve, and the latter to exclude the water. The lower ends of the shafts are in the shape of an inverted cone, and revolve on metal steps fixed in the bottom of the wheel openings or cases. The upper ends of

the water-wheels are connected to the steamengine by a crank or wheel. The middle parts of the paddle wheels are made hollow and water-tight, that they may be light and buoyant, so as to relieve their shafts from weight and friction.

3. The third improvement, which relates

to the steam-engine, and by which it is stated "additional power may be obtained, and the noise commonly produced by the escapement of the steam in its passage from the cylinder is avoided or lessened," consists in making a communication by means of a pipe between, and from the escape pipe or opening of the cylinder to the centre of the upper part of the propelling wheel case encompassing the submerged paddle wheel, so that not only does the wheel case serve as a sort of exhauster to the engine, but "the centrifugal action given by the paddle-wheel to the water contained within the wheel-case, is made to condense the escaped steam."

The claim is, 1. "To the application of shield decks to vessels constructed of metal or wood, whether propelled by steam power or any other power." 2. "To the application of submerged propelling wheels upon the principle described, whether placed vertically, horizontally, or obliquely, for the purpose of propelling vessels." And 3. "The method of using the steam-engine for the propulsion of vessels, by which the submerged propelling wheel-case or apparatus is made to serve as an exhauster or exhausting medium, and the water contained within the wheel-case in which it revolves, as a condenser, thereby conferring all the advantages of a condensing engine with the lightness and simplicity of the high-pressure steam-engine, with also the noiseless action of the former."

HENRY HOUGH WATSON, OF BOLTON, IN THE COUNTY OF LANCASTER, CONSULTING CHEMIST, for certain improvements in dressing and finishing cotton and other fibrous substances and textile and other fabrics, part or parts of which improvements are applicable to the manufacture of paper, and also to some of the processes or operations connected with printing calicoes and other goods. Rolls Chapel Office, June 21, 1842.

These improvements, as far as regards dressing, consist, firstly, in the removal, by singeing off the fine protruding fibres and loose filamentous matter from the articles and goods mentioned; and secondly, in impregnating the articles and goods with a certain solution, mixture, or size, by which the articles when dried have additional body and stiffness given to them, and the fine fibres which before protruded are caused to lie down.

The improvements in the first description of dressing are carried into effect by submitting yarn, thread, and textile and other fabrics, whether comprised of cotton or any other organic fibrous substance, or of any mixture of organic fibrous substances, to the action of air, either atmospheric, or that