interfering with the action of the main shaft. When the paddles are in full action, one-half turn of the steering-wheel B renders them entirely passive; and if this be effected on one wheel while that on the other side remains in full force, the vessel is brought short round upon her heel, independent of the rudder, which may, however, be used at the same time.

From the water-line in the drawing, it will be seen that it is intended to place this wheel so deep in the water that no alteration in the loading or the trim of a vessel can sensibly affect its propelling power; in fact, unless a vessel be thrown nearly on her beam-ends, such a wheel as this can never be entirely out of water. Should the revolving-paddles ever become from any cause unmanageable, the fixed paddle-frames may be closed, and the paddles secured in that position by passing the rod, before spoken of, through the fixed frame radial bars merely; the wheel may be thus converted in a few minutes into the common paddle-wheel.

The fixed frames are so secured to the body of the wheel, that they may with their paddles be entirely removed in a few minutes without interfering with any other part of the machine; they may be replaced also in an equally short space of time. And when the fixed frames are so removed, the wheel will remain as effective as before.

Nearly the same effects may be produced in a different manner. Suppose the forward movement of the vessel to be effected as previously described, and that the command is given to 66 stop her." The stopping of the main shaft would merely arrest the propulsive power of the wheel, which in many cases is all that is desired; but should it be wished to add a drag upon the vessel's way, this may be regulated to any extent-from a mere line to the entire superficies of the whole of the immersed paddles-by a half-turn of the steering-wheel B, or so much less than a half-turn, as may be deemed suffi cient. A reverse motion of the main shaft then gives the back action.

In order to protect the wheel from gunshots, it is intended that wheels on the principle of this patent shall be wholly submerged when applied to vessels of

war.

The arrangement shown in figs. 1 and 2, without the fixed frames and their paddles, would he suitable for such a

purpose; but it will probably be found, in most cases, necessary to reduce the diameter of wheels so used, and to increase the number of their revolutions proportionately.

Following out this idea, let us suppose that the fixed frames with their paddles are removed, and that the highest paddle remaining is completely under waterthe wheel propelling in the direction of the arrow. Now, a half-turn of the steering-wheel B would, without reverssing or in any way interfering with the motion of the main shaft, instantly give back action equal to the fore action on the other side of the vessel; so that this movement of the steering-wheel B being performed on one of the two wheels only, the effect would be to bring the vessel round upon a point within her keel, and to make her turn gradually round upon that point as long as the wheels in that position could be impelled. A man-ofwar would thus have the advantage of being able to bring her broadsides to bear in succession upon any given point by a regular movement, without any effort beyond the first adjustment of the wheelsthe whole not the work of one minute.

The wheels in the case last supposed are assumed to be not only submerged, but in a vertical position like that of the common paddle-wheel. Mr. Pickworth, however, considers that his wheel would be quite as effectual a propeller, if attached to a vessel in a horizontal position, as in any other. All that is thought to be necessary is a modification in the arrangements of the vessel. A great breadth of beam, with a light draught of water, are the obvious requisites for a vessel with horizontal wheels; and these, it is presumed, might be combined with advantage for passenger-vessels and for war purposes. A vessel of the form somewhat like that displayed in the engravings, figs. 3 and 4, might perhaps be found suitable.

Fig. 3 is a side view, and fig. 4 bottom view. A, the gun or passenger deck; B, main-floor of the boat; C, the keelfloor; D, engine-room; E, wheels; F, rudder; G, the position which the wheel E would occupy if placed vertically in the usual manner; HH, coalholes; and I, line of floatation. Any modification of this arrangement which may suggest itself to the scientific builder might be very readily introduced. For

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example, the wheel itself may be made buoyant by a drum on the main shaft, if such an adjustment should be thought desirable.

We We are inclined, on an impartial consideration of the whole subject, to think that Mr. Pickworth has rather attempted too much by striving to combine all the advantages of the best form of moveable float-boards with all the advantages of the common paddle-wheel; while, at the same time, to avoid the disadvantages of both one and the other, he has given a degree of weight to his wheel which may weigh considerably against it. It is, however, but justice to remark, that by a judicious arrangement of his materials he gets the needful strength with perhaps as little weight as possible. He will, we hope, excuse us for suggesting, that his paddle-frame vertical bars might instead of plates of metal have rods (following the outline of the plates) substituted for them with advantage. In the case of a sea striking the wheel on its broadside, the rods would offer less resistance than the plates.

We beg these remarks to be understood as applying to figs. 1 and 2 only, for upon the horizontal wheel we do not venture to give an opinion; all that we can say is, the arrangement seems to us to be ingenious and worthy of consideration.

We are informed that it is the intention of Mr. Pickworth to charge no paténtee's premium upon his wheels, but to give permission to all respectable engineers to manufacture them, on condition of his being paid a small annual charge upon every vessel to which they may be applied, so long as she may continue to use them. This, at all events, is a proof that no advantage is desired by the ingenious inventor other than what the real and positive superiority of his wheel may procure for him.

BRIGHTON RAILWAY BILL. The Evidence against Tunnels. Sir Anthony Carlisle, M.D., examined by Mr. Hill.

I am vice-president of the College of Surgeons, and have been a public practitioner about forty-four years in London. As a part of my professional duty, but more especially in my scientific pursuits, I have attended to the subject of tunnels on railways. It must

necessarily happen that at very few seasons of the year there can be the same temperature in the external atmosphere and the stationary air in the body of the tunnel; there must necessarily be some marked difference, for in the winter season the air in the tunnel will be considerably warmer, and in the summer season the air in the tunnel will necessarily be colder than the external air. Such a variation of temperature will expose persons in health to the common affection notoriously termed catching cold, the source of other disorders; they may be inflammatory or they may be of other kinds; but the common phrase of catching cold, I believe, arises from its being found by experience that people are apt to take a disorder called a cold or catarrh by sudden transitions from heat to cold or from cold to heat. I entertain no doubt that the variations in temperature to which I have referred will be sufficient to put persons even in health in danger of cold by passing through a tunnel. I think it must of necessity be." so; for although a person may pass sometimes with impunity, he cannot be always assured of passing through a tunnel under the stated circumstances with impunity. Most striking effects would be produced on persons of weak constitutions or who are invalids. If your lordships and the Committee will permit me, I will generally state, without being too prolix, the reasons for my entertaining this opinion. The surface of the body and the inner surface of the lungs are the two portions of the living frame most exposed to the vicissitudes of temperature in the air. Persons with weak lungs being subjected to the alternation of heat and cold or cold and heat, by such transitions must necessarily have disordered conditions of the lungs aggravated; so in the influences upon the external surface of the body, catching cold is commonly and justly imputed to the external application of change of temperature; hence persons are said to "catch their death of cold in damp sheets," and on exposure to a current of air, because the current of air, though of the same temperature, does not accord with the temperature or halo immediately surrounding the living body, which in a healthy man is at 100 degrees, such halo surrounding his body approaching nearer to the temperature of his body than to the external atmosphere; and hence, if a stream of air blows upon him, it produces a sensation of cold, and in fact it has the effect of a different temperature from that which envelopes or surrounds the person. Besides catching cold in passing through a tunnel, a person is subjected to all the modifications of disorder of the lungs which have a tendency to inflammatory nature, active or chronic; and also erysipelas, a very dangerous disease, is known very frequently to hap

pen from sudden transitions from heat to cold. Rheumatism, in its various forms, lumbago, both acute and chronic; that is, active or long continued. I would not permit one of my patients to go to Brighton by a railway that had a tunnel in it; I should endeavour to dissuade any patient of mine from subjecting himself to such perils. I should prefer that the patient should go by an open carriage on the open road in preference to going through a tunnel, for the reasons I have assigned; I would not hesitate about it. I have no expe rience about the length of tunnels; I know something from experience of the difficulty of changing masses of atmosphere either in tunnels or in a large room; it is impossible to change the atmosphere in a large room, and I apprehend it would be impossible to change the atmosphere of a tunnel 600 yards long. The observations I have made apply to a tunnel of five or six hundred yards. I have understood the tunnel in question is to that extent. I think a patient might safely go by an open railway; rapidity of motion to a delicate person would be an objection, since there would be an extraordinary change in the blanket of air belonging to the person in going along. The air in the interior of the tunnel is not precisely the same as that without; it is stationary air, having a different temperature; and it has also a commixture with other gaseous substances; it is also a damp air; if it was a warmer air than the ambient atmosphere, I think in that case speed would make it less dangerous. The majority of cases in which persons catch cold have been from going out of heat into cold; there is, however, danger on being exposed from cold to heat; many persons catching cold from sitting over a fire, or from going into warm rooms; 1 do not speak conjecturally.

Cross-examined by Mr. Serjeant Merewether.

I have no experience beyond the rationale I have endeavoured to give upon the subject, which is, that the change of atmosphere surrounding the individual produces the effect of chill or cold to the surface of the body; but that can be remedied by warm clothing or a close carriage. I have not arrived at the conclusion, that a slower conveyance is better, inasmuch as it may be an object that a weak person should be suddenly transferred from London to Brighton. I have stated that the atmosphere in the tunnels I assume to be nearly stationary. I do not know what length of tunnel would ventilate itself practically; but I know something about the matter with regard to wells and borings of other kinds, and 1 have had some experience upon the subject; a well would be in different circumstances from a tunnel, which would be open at both ends, whereas in

a well there would be only an opening at the top operating upon the well. I know from experiments that a tube filled with air of considerable dimensions does not easily discharge its air by any external force employed upon the confined air, but the contrary, because of the elasticity of the air,-its propensity, if I may use such an expression respecting a passive thing,-is to avoid pressure, and to get behind any compressing force, as in the case of pressure from a piston or any thing of that kind; I know from experiments it is difficult to discharge a tunnel or a large room of any stagnant or quiescent mass of air; and I believe a 600 yards tunnel of the dimensions given would neither discharge itself nor could it be discharged by any ordinary known means. If there should be a difference in the atmosphere in the tunnel, and at the two ends of it, there would be a natural tendency in the air to equalise the difference; that is to say, if the air is colder on the inside it would have a tendency at the ends of the tunnel to mix with the atmospheric air; and, vice versa, if the air in the tunnel was warmer than the air outside, it would have a tendency to equalise itself with the external air; but this only to a limited extent; the two atmospheres, the atmosphere within and the atmosphere without, being on a different balance, would soon strike the balance in the length of a tunnel of 600 yards, and I think long before they arrived at midway; so that you could not expect from any change of temperature a current of air to pass through the whole of the tunnel. Shafts let down in the middle of the tunnel, or in other places, would have but a very limited tendency to create a draught in the tunnel; for in the attempts to ventilate, with submission, the late House of Peers and the House of Commons, the most scientific persons were consulted, and every means were devised; but I believe the means were not effectual to discharge the air confined in those rooms, although not very large, and to have pure and refreshing air introduced in its stead. I am not practically acquainted with the effect produced in cases where such shafts have been introduced into tunnels. I know that in rooms a shaft in the roof has not had any good effect. I have seen two tunnels near London, the one near the Harrow- road, and the other near Islington. I have attended to that as to my own feeling. I have walked part of the way through them, and have ascertained that the feeling corresponds with my theoretical view, and what I have read on the subject, and what I have said corresponds with my own feelings. The tunnel I refer to near Islington Hill is completed; it is for a barge-way; but there is another also near the burying-ground at Kensal Green. I

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walked through part of the way; it is not finished; the centres and other impediments all in the way, but machines driven by steam were going into the tunnel; the tunnel was carried quite out to the other extremity, I believe; there was a light visible at the other end. I do not think that a shaft in the middle of a 600 yards tunnel, or two or three shafts, would have any great and efficient effect in discharging the quiescent air, or of moving it out at either end, or even upwards; that is my opinion. Supposing there were shafts, and there were carriages propelled by steam passing frequently through the tunnels, my opinion, founded on analogy, and not from any personal observation, is, that the ventilation would not be efficient. I do not think that would be an effectual check to the stationary temperature, or that a stationary air would be removed. I have gone with scientific persons to visit mines. I was brought up in the county of Durham, and knew the coal-pits then. I had the charge of two or three coal-pits when I was young. The workmen insured medical attendance by paying so much a week; we had a good many patients. They were not more than twelve hours out of twenty-four in the pit; but it is so long since. I cannot charge my memory with the number of hours, but they had a great deal of holiday above ground. They are healthy men generally; but asthmatic men, I believe, could not work; and there was a singular thing happened in regard to horses which were worked in the collieries-it was the prevailing opinion, that a horse brought up in the collieries when he came above ground went blind. cannot say that he was generally very fat when he came up, but he went blind, and the pit-horse was not a saleable horse. If the engine goes at the rate of fifteen miles an hour, the half mile would, of course, engage two minutes, and the time calculated for thirty miles per hour would be one minute for the transit through the tunnel, so that there would be three changes operating upon the individual, provided the air were different on the transit from the atmosphere to the tunnel, and on the transit from the tunnel to the atmosphere again, thus making three dips. If a hale person, undergoing the exercise of travelling upon a railroad, comes to a tunnel which he will be a minute, we will suppose, passing through in a carriage, still undergoing the motion of the carriage, I do think he will be likely to catch either cold or catarrh; and my opinion is founded on long experience; the transition would endanger a person even during the duration of one mi

nute.

I

I have known a person to become erysipelatic from a minute's exposure to the air, and the change occasioned by it; a man of some celebrity lost his life from that very

circumstance within the last month, Mr. Barry O'Meary. He was sitting near a window, he felt himself cold from the air of the window, and he changed his place, and from that exposure he went home and took to his bed and died. I say it is the same thing in effect, whether the carriage draws the individual at the rate of thirty miles in the hour, or the wind travels at the rate of thirty miles an hour, since they equally affect the person; it would be the same as to the person, whether on the surface of the lungs or on the surface of the skin, with this difference, that in the open air the air would be uncontaminated, while within the tunnel the air would be mingled with deleterious matters. Under the circumstances propounded, a person is likely certainly either to catch cold on the surface of the skin, but preferably the catarrh of the lungs; I say that in a transit of only one minute he is in peril, and I would not so expose myself. A hundred persons may pass through with impunity, and the next five may all be seized with some dangerous illand for that reason I would not recommend a man to go through a tunnel. I do not mean to say it is 100 to 5, I only speak hypothetically. Certainly many may pass through without any difficulty. Supposing they went through in a carriage, pulling up the window for a time would operate as a considerable preventative; but that would also come to a moral question, whether the passengers choose to have the window up generally; for in stage-coaches half the passengers wish the window up, and half wish to have it down. The ratio of any bad consequences would be much in proportion to the length of the tunnel. The pulling up the windows would be a certain degree of protection, but I cannot say how much.

ness,

Re-examined by Mr. Hill.

I have heard that on railways persons travel in two classes of carriages, one open and the other close; but I have not seen it. Persons may go into crowded hospitals where they are in great risk of contagion, and yet not take disease; they may visit a house or a place having a patient affected with the plague, or they go and visit a person with the cholera, and not take the contagion, and that produces a paradox in the medical world on which there is a division of opinion. A person escaping would not be a sufficient ground for placing himself in those circumstances. The air of a tunnel is impregnated with other gases, which makes it very different from the outward air. Sulphuretted, carburetted, and carbonic gases would be emitted from the burning of the coke, and the vapour of the steam would be condensing and would keep the atmosphere damp; and you would have also the effluvia and respi

rating products of the passengers going through, assuming hypothetically that the atmosphere is little, if at all, changed, the mass of it in the middle of the tunnel; so that a quantity of stationary or stagnant air would remain impregnated with poisonous gases, or impregnated with the effluvia of the passengers; it might be with scarlet fever or the small-pox. It is my decided opinion, from all the facts and all the consideration I have given to the subject, that the air in the interior of tunnels is in nearly a stagnant state. I think it is reasonable to conclude, as it is philosophically evident, that there must be a progressive accumulation of unwholesome or unsafe atmosphere within the tunnel, unless it can be wholly drawn or driven out in a mass, and I am not aware of any method by which to discharge it; hence there must be a progressive accumulation of evil. I know that a minute is quite sufficient to produce catarrh. It is just the rapid transition from the outward air into the tunnel, and then again into the outward air, which creates the danger. It is like exposure to the wind, and every body knows when wind is cold; in winter, although under a hedge where cattle would seek shelter, you do not feel it, notwithstanding the wind is blowing from the north. The three sudden transitions are not favourable to health; getting into an atmosphere of sixty, and making an exit from the tunnel again at thirty, must expose a person to three vicissitudes within half a minute or a minute, as it may happen. With respect to the comparison between persons going through a tunnel to persons going into a mine, very great care is taken, and very great expense incurred for the purpose of ventilating mines; those who go into mines for the purpose of labour do not expose themselves to those very sudden variations. They are tolerably well clothed, and they all take care of the inward man; they are all drinkers; but whether that does good or harm I will not say. Even considering the horses do get fat down in the mines, I would not think of sending invalids and timid and delicate persons down into mines. There have been various projects, and there is nothing, however absurd, that has not been tried in medicine; but I believe it was never yet tried to send a person into a coal-pit to cure him of any disease of the lungs. Dr. Beddoes tried experiments by artificial airs, and putting people into cow-houses, and the Lord knows what; but I do not believe that his schemes have been followed by any of his brethren. I should not send my patients to a wateringplace, if the way to it were to lie through a coal-pit. Persons retain their health in coalpits, so do some also who work up to their middle in water; but that would be a very bad reason for recommending that to a per

In

son affected with disease of the lungs. bleaching-grounds I have seen men at four in the morning with the dew on the grass, which is very cold, working with bare feet; I believe they are a healthy class of persons; but when I went fishing on the same grounds, I took care to have good elastic water-proof boots. Railways, inasmuch as they furnish the means of rapid and easy transit, I consider to be very favourable to invalids. They would not be exposed to dust or rain, I apprehend, and the transit would be rapid: and by proper clothing and proper attention to the windows of the carriage, they may avoid any danger. I would not hesitate to send a person with diseased lungs by railway to Brighton; but I would not send him through a tunnel. It would be a great public benefit to have railroad conveyances for invalids without a tunnel.

Mr. Serjeant Merewether.

---

There have been means used for ventilating the House of Commons; cannot the same means be used for ventilating tunnels?-I believe the same means cannot be applied; I should think not.

Examined by the Committee.

A

The same danger would occur to a person passing through those different temperatures of air, at the rate of thirty miles an hour, that would occur to him if the air through which he passed travelled the same rate; the cases would be analogous. protection might be afforded by clothing. Water-proof clothing would protect a person against the vicissitudes; how far that would operate in an open carriage on a railway, I cannot say. In a warm room there would be a quiescent temperature; but in the alternate atmosphere affecting a man's body when passing through a tunnel he would pass through a general change of atmosphere, which would wash off, if I may use the expression, the local atmosphere around him. Going at the rate of thirty miles an hour would increase the circulation very little. That sort of agitation in a carriage is not considered productive of a great deal of accelerated influence on the circulation of fluids, to use a pedantic expression. Supposing that to take place, it might or it might not prevent the danger of that accelerated transition; if it increased the natural heat of the body, it would expose the body to the vicissitude of cold much more than if it remained in a temperate medium. If, instead of going in a carriage drawn by steam through a tunnel, the individual were to run through it, there would be the additional consequence of the increased circulation of blood, for running accelerates the circulation of blood very remarkably, but not the motion by travelling in a carriage at thirty miles an hour. The chief difficulty found in ventilating the Houses