§ 2. Of the Levers and Spring-Balance. cannot generate a sufficient quantity of on the sides of the vessel a pressure, which || to be continually jerking, and consequently steam. But when a speed of eight miles is the result of its elastic force, and which opening and shutting continually the valve, per hour only is required, and for an aver- gives the exact measure of that force. If, the weight was replaced by a spring, and age train of twenty-four wagons, which, in the vessel being already filled with steam, that is the manner in which the valves are going up the line empty, are equal to a a fresh quantity is continually added, the at present constructed. load of about sixty tons on a level ground, elastic force of the steam will augment the most convenient boilers have been more and more, and consequently also the found to be those with one returning tube. pressure it produces on every square inch They generate a sufficient quantity of of the surface of the vessel. Now, if at steam for the work required of them, and one point of the vessel there be an aperhave the advantage of being cheap in re-ture, closed with a moveable piece supgard to prime cost and repairs, as their form porting a certain weight, it is clear that, is simple, and they are entirety made of as soon as the steam contained in the vesiron, whilst the tube boilers require the use sel produces upon the moveable plate a of copper. pressure equal to that of the weight which holds it down in the opposite direction, the plate will begin to be lifted up; the passage will then be opened, and the steam escaping through the aperture, will show that its pressure was equal to the weight that loaded the plate or valve. Besides the difference in the form of the boilers, the other parts of the engine differ also. The cylinders are placed on the outside, and in a vertical position. The motion is not communicated from the piston to the engine by a crank in the axle, || but by a rod on the outside of the wheel, resting upon a pin fixed in one of the spokes. Those engines have in general six equal wheels, of four feet diameter each. Two of the wheels are worked by the cylinders, as has been just explained; and the four others are attached to the first by connecting rods, that cause them to act all together. The weight of these engines varies. Setting aside the three which we have mentioned as being on the model of the Liverpool ones, and which weigh only about five tons and a half, the average weight of the others is from ten to twelve tons. All those engines are supported on springs. In some of the older ones, the water of the boiler, pressing upon small moveable pistons, and pressed itself by the steam contained in the boiler, was intended to supersede the springs; but though that system displayed a great deal of ingenuity, the spring it formed was found in practice to be too variable, and the system was given up. The usual proportions adopted for the engines on that railway are the following Cylinder 14 inches. Stroke Wheels Weight 16 It will easily be conceived that no exact calculation can be established of the power of locomotive engines, without knowing exactly the pressure of steam in the boiler, which is the intenseness of the propelling force of the motion. If we were to depend on the nominal pressure of the engine, that is to say, the pressure declared by the constructor, great mistakes might be incurred: for it sometimes happens that, with a view to appearance give to a locomotive engine the of executing more than others, though at the same pressure, its pressure is declared to be 50 lbs. per square inch, whilst it really is 60 or 70 lbs. Moreover, the calculation of the pressure is generally so incorrectly made, that scarcely any dependance can be placed upon it. We have therefore been obliged to make a particular study of that part of our subject. It must, however, be observed, that the resistance which opposes the egress of the steam does not consist only in the weight that has been placed on the valve. Besides that weight, the atmosphere produces also on the valve a certain pressure, as well as upon every other body with which it comes in contact. That pressure is known to be We shall first give the manner of ascerequal to 14.7 lbs. per square inch. It is taining the pressure by weighing and meas therefore the weight, added to the pressure uring the different parts of the valve appa of the atmosphere, that gives the real meas-ratus, in case one should have no mercurial ure of the elastic force of the steam; while gauge. We shall afterwards show the the weight alone represents only the sur- cause of some mistakes which may be inplus of the pressure over the atmospheric curred by that mode of calculation, and pressure, or what is called the effective which are avoided by using the mercurial pressure of the steam. Consequently, steam-gauge. Lastly, we shall point out when a valve has a surface of five square the uncertainty to which also that instru inches, and supports a weight of 250 lbs.,||ment is liable, and we shall propose another which, divided between the five square to be used instead of it. inches, gives a resistance of 50 lbs. per We have said, that, to produce on the inch, that amount of 50 lbs. expresses the valve a great pressure without being eneffective pressure of the steam, a valuation cumbered with a considerable weight, a frequently made use of on account of its lever is employed. M (fig. 16) being the convenience for calculation, whereas, 64.7 boiler, and S the valve, C is a fixed point lbs. is the real resistance opposed, and to which is fastened one of the ends of the therefore the real pressure of the steam. lever BC. The lever presses at the point A on the valve by means of a pin, and at the point B it supports a weight, or to speak more accurately, it is drawn by a spring equal to a given weight. This is the principle on which are established the means of judging the amount of pressure in locomotive engines. How ever, as those engines are required to work with at least 50 lbs. effective pressure per square inch, and as, in order to give passage, 48 lbs. per sq. in.if necessary, to all the steam generated ined at the point B, or at least the weight re 4 feet. 11 tons. Effective pressure the boiler, a valve must not have less than The diameter of the valve, the proportions of the lever, and the weight suspend presented by the tension of the spring being given, it will be easy to deduce from them the pressure resulting on each square inch of the surface of the valve. And, vice versa, it will also be easy to know what weight ought to be applied to the point B, in order to produce at A a given pressure. For, if P represent the weight suspended at B, that weight will produce on A a pressure Px whole It was therefore necessary to produce BC AC which will consequently be the pressure produced on the valve; and S represent the surface of the valve in DING TO THE LEVERS AND THE SPRING- portion of 5 to 1, a weight of 50 lbs. sus- inches BALANCE. § 1. Of the principle on which that calcu lation is founded, Px BC AC will be the pressure pro S pended at the end will be sufficient to pro- When an elastic fluid is confined in a the rapid motion of the engines, a weight The levers and valves used by the dif olosed vessel, it produces in every directioneuspended at the end of a lever was found ferent constructors of engines vary con siderably in their proportions. But, among those proportions there is one, first used by Mr. Edward Bury, of Liverpool, which possesses an uncontested advantage over all other combinations of that sort. It consists in taking for the proportions between the two branches of the lever the ratio of the area of the valve to the unit of surface. By that means the weight P suspended at B gives immediately the pressure produced on the valve per unit of surface. Supposing it should be required to establish a valve of 24 inches diameter, which make very nearly 5 squre inches surface, and that. in consequence, the ratio between the two branches of the lever has been taken as 5 BC 1 P ex to 1, that is to say, that BC be P X- = AC to it, the divisions may easily be verified, aperture of the lever at that place, and pressure, if we be the total weight on the valve, and the the steam will be known, for the degree with the disk, 8 lbs. 8 oz., and divided be surface of the valve being 5 square inches, the weight or pressure per inch will be 5P =P. The same would take place if, 5 having a valve 3 inches in diameter, which gives 7 square inches for the surface, the ratio between the branches of lever were to be taken as 7 to 1. We have said that, to the weight which ought to be snspended at the end of the lever at B, is substituted the equivalent pressure of a spring. This spring is a spiral, which by being more or less compressed, is able to support in equilibrium, and consequently to represent larger or smaller ance, such as is used for weighing in daily Occurrences. bar mn. then marked by the index will show the §3. Of the corrections to be made to the tween the 5 square inches, a little more than 1 lbs. per inch. placing it in the basin of a common pair of scales, the weight of each of its parts may easily be calculated, and consequent ly also the weight of the rod and spring. In fact, the degrees having been marked on the balance when in its usual situation, index stood when the spring bore no weight zero was inscribed at the point where the at all, or more exactly when it only bore the weight of the foot. Afterwards fresh 2. To know the weight of the part of the balance supported by the lever, the balance ought to be taken to pieces, and The mode we have just explained is the the spring with its rod weighed separately. one commonly used to calculate the pres- However, this operation may be avoided sure on the valve. However, it will easily by taking the balance in one's hand, and be conceived, by the manner in which the suspending it in the contrary direction in spring-balance acts upon the valve, that, which it is placed in the common act of to know the pressure which really opposes weighing, that is to to say, with the foot the egress of the steam, it is not sufficient above and the rod below; the weight to read the degree where the index stops, marked by the index will then be equal to and to calculate the effect produced at the the difference between the weight of the end of the lever, as we have done above. rod and spring, and the weight of the weights. In other words, it is a spring bal-In fact, first, besides the weight represent- foot. If, therefore, the total weight of the ed by the spring, and which would be sus-balance be known, which is easy, by pended at the end of the lever, it is clear that the weight of the lever itself causes a This balance consists of a rod T (fig. 16) certain degree of pressure; for before the which is held in the hand, and to which is steam is able to raise an ounce of the fastened a plate with a narrow oblong aper-spring, it must raise the whole weight of ture in it. Behind this plate, and in a the lever. The same takes place in recylindrical tube, is a spring, the foot of gard to the disk of the valve, which must which rests on the basis L, which is fixed be raised before the steam can have any to the plate. At its other end, this same action on the balance. 2. When any obspring is pressed by a moveable transverse ject is weighed with the hand, that object At the bottom of the aparatus is is suspended at the bottom of the balance, a rod P, to which are fastened the objects but then the hand supports the upper part, that are to be weighed. The prolongation that is to say, the rod, with the spring to of the bar mn projects throngh the aperture which it is fastened; and that effort is not of the plate, and is terminated by an index taken into account, because it does not make which appears on the outside, and which a part of the weight. Here, on the con slides up and down the aperture, in propor- trary, the rod, the screw, and the spring, tion as the spring is more or less com- are an additional weight really suspended pressed. Divisions are engraved along that at the end of the lever, over and above the same aperture. In order to mark them, pressure marked by the spring; they must known weights of 1 lb., 2 lbs. &c., are suc-all be raised before the spring can be prescessively suspended at P, and according sed upon in any way, and can register any as those weights, by pressing on the spring, effort; they must therefore be taken into cause the index to rise, the corresponding account. The true pressure which takes divisions are marked. The consequence of place on the valve will consequently not this is, that when an object of unknown be known, until are added to the weight weight is suspended at P, and makes the marked in the balance: 1. The pressure index rise to the point marked 10, that is to produced by the weight of the lever at the say, to the same point to which a known place of the valve: 2. The pressure proweight of 10 lbs. made it rise, we conclude duced at the end of the lever by the weight that that object also weighs 10 lbs. This of the rod and spring of the balance. is the sort of balance which is used for measuring the pressure in locomotive en gines. We see that, by taking it off from the engine, and suspending known weights weights were successively added, and for each of them the corresponding number was inscribed on the plate, always omitting the weight of the foot, which in fact ought not to be reckoned. The numbers inscribed on the plate represent, consequently, the real tension of the spring, less the weight of the foot of the balance. Now, by turning the balance upside down, the spring is drawn by the weight of the rod and spring which it then bears. If it had borne a weight equal to that of the foot, it would have marked zero; if, the efore, it marks 2 lbs. or 3 lbs., the rod and spring weigh 2 lbs. or 3 lbs. more than the foot. Supposing thus: B to be the total weight of the balance, T the weight of the rod and spring, and P' the weight of the foot; if the balance turned upside down shows m weight, we shall have 1. To know the effect of the lever on the m = = T P'; valve, the lever must be unfastened from but, on the other hand, the weight of the the balance; a string must be wound balance is equal to the weight of its two round the pin A, or passed through the parts, or B = P' + T: T= 4+1.5 B+m = 2.75 lbs., which is the weight to be added at the end of the lever; that is to say, to the weight already marked by the balance. which they completely fill, it is very clear inferior diameter, an error will thus be com adding therefore together these two equa- that the steam can only act upon their in-mitted of 5 lbs. pressure per inch, which tions, we find ferior surface; consequently, the area we error might be still greater if the raising of have here above expressed by S, must be the valve should happen to be more consid B+m 2 T, or Ttaken after the inferior diameter of the erable. Moreover, as there is no practical valve. By calculating in that manner, the means by which to learn by how much the When the valves have a lever of 15 inch-exact pressure will indeed be found for diameter of the valve is augmented by the es only, the balance used weighs general-every case in which the valve still touched raising, the consequence will be that the ly 4 lbs., and when turned upside down, the seat, or, if raised at all, was only so for mode of calculation explained here above, it marks 1 lb.; so in that case the weight, an instant, or in a very small degree; but even with the corrections we have made, of the rod and spring is whenever the steam, being generated in will apply exactly only to those cases greater quantity than it is expended by where the valve just begins to be raised, the cylinders, escapes with force through or lets scarcely any steam escape; but the the valve, it raises considerably the disk of greater the raising the more the calculathe valve; the consequence then is, that, ted amount will surpass the real pressure. instead of acting on the inferior surface of We shall see hereafter examples of this. the valve, it evidently acts on a greater But still this is not all. If the pressure surface, and which is the greater the more of the steam in the boiler must be deduced the valve is raised. For instance, in fig. from maasurements taken on the engine, it 20 it acts on the surface cd instead of act- must also be observed that it frequently ing on ab. In that case the area S ought happens, in order to make the construction to be calculated on cd, and not on ab. But more easy, that the miter of the valve is how are we to know cd, unless we calcu-made to join the sides of its seat only withlate it by the rising of the valve, which is in a certain breadth, as may be seen in fig. a very difficult, if not an impossible, opera- 21. The consequence is, that the surface adding therefore those weights to those tion? Moreover, the difficulty is complica- ab, or the inferior part of the valve, which marked by the index of the balance, and ted by the circumstance that, from a to b has been measured, is not the surface upon taking besides into the account the weight the pressure of the steam acts directly to which the pressure is divided. The real of the lever, as mentioned above, we shall raise the valve; but from e to a and from diameter in this case is cd, If therefore then have the real pressure produced by to d the action of the steam takes place there be between ab and cd a difference, the whole apparatus on the valve. Di- only in a lateral direction, and according to for instance, of one-eighth of an inch, this viding it by the area of the valve, the re- an angle, which varies in proportion as the difference may produce, as well as in the sult will be the pressure effected upon each valve is more or less raised. case of the raising of the valve, a difference of 4 to 5 lbs. in the Mis When the valve has a lever of 3 feet, the balance requires smaller divisions. It usually weighs only 2 lbs., and turned upside down, marks 14 lbs., which gives in that case for the weight of the rod and spring T= unit of surface. 2+1.5 1.75 lbs.: From this we see that, with a long lever, the error of pressure per square inch may amount to 7 lbs. or 8 lbs., and that, even with a short lever, it may be 3 lbs. or 4 lbs., which is still considerable. Keeping the preceding notation, that is to say, being the weight shown by the index, T the weight of the rod and spring, L the weight of the lever, weighed as mentioned above, and D the weight of the disk, lastly BC and AC being the arms of the lever, and S the surface of the valve in square inches, the pressure produced per unit of surface will be (P+T) +L+D BC The effect of this alteration in the diam. inches at the top, of which we shall find 2 x 3.1416x 2.5 4.91 sq. inches, has become It is for not having taken these considerations into account that we find so often on locomotive engines spring-balances, which are supposed to be fixed at 50 lbs. pressure per inch, but which are really fix-x 3.1416 × 2.625 5.41 square inches. ed at 55 lbs. or 60 lbs. We shall soon have frequent occasion to apply and verify these principles, which by that means will be rendered perfectly clear. § 4. Of the Miter of the Valves. These are not the only causes from which errors may result. There are two others which are frequently met with in the valuation of the pressure of locomotive engines, and which are not so easy to correct as those we have just mentioned. Consequently, if we suppose the total weight supported by the valve, including the levers, rod, disk, &c., to be 245 lbs., that weight, when the valve is shut, will represent a pressure per square inch of different pressures of steam, when the valve In order that the valves may exactly by which we see that the same weight close the opening to which they are ap-marked by the balance corresponds to very plied, without being subject to contract an adhesion with the seat that supports them, it is necessary to make them slightly conical, or at last with a slanting border. When these valves rest upon their seat, Continuing, in the case of a blowing valve, to calculate upon what is called the diameter of the valve, that is to say, on its pressure. takes may be avoided in that respect, by the valve, but also the diameter of its seat. measuring not only the inferior diameter of There still, however, remains the blowing of the valve, the exact appreciation of which escapes all manner of calculation. The mercurial gauge, which we are going to describe, is the means of avoiding both causes of error; but that instrument is expensive, and as yet so scarce, that in all the factories and on all the railways, except the Liverpool one, there is at present no other mode of ascertaining the pressure than those explained above. ARTICLE II. OF THE MERCURIAL STEAM-GAUGE. § 1. Construction and use of the Mercurial Steam-gauge. The calculations we have made may be sufficiently exact for a great number of cases. Still they present some degree of complication that makes them inconvenient; besides, they cannot be made without measuring and weighing different parts of the engine, which operations require time and gine is at rest. care, and can only take place when the enWe may therefore easily conceive the great utility of an instrument which at first sight, and by its bare inspection, will give the exact measure of the pressure of the steam. By means of such an instrument, all cases, even those of the raised valve, present no longer any difficulty, and the necessity of calculation itself may be dispensed with. The only thing required is, the possibility of submitting the engine to the proof. of pressure which would make the result umn of mercury, the weight of which we The instrument used with that view is, ||immediately rise in it to a considerable and all high-pressure steam engines it is the mercurial steam-gauge, constructed on height, and cause by that means a surplus this which is to be considered. The colthe same principle as the common barometer. M bm (fig. 18) is a tube containing mercury, which ought not to rise above the two points M and m. FG is the water reservoir. It must not contain water above the cock E, the use of which is to get rid of the surplus of water that may have been produced by condensation on some former experiment. R is an opening closed by a cock, and through which mercury or water may, when wanted, be introduced into the instrument. Lastly, C is an ajutage on which a tube is screwed, the other end of which reaches the boiler of the engine. This tube is flexible, and usually made of tin; it forms the communication of the mercurial gauge with the engine. At the point where it reaches the engine, it is screwed on an ajutage fixed to the boiler, and kept close by a cock. By the same reason d' being the density of the water, the weight P' of the column of water will be expressed by go'br, its basis being also b, and its height Mr' But the density of the water being expressed by 1, that of the mercury is expressed by 13.568; thus we have of 1 13.568 or = б 13.568' P' = gobr 13.568 gobx 2gibx 13.568+gobh, 1 13.568 =h. 13.568 This equation gives = x. To graduate the scale of the instrument, we may begin by marking, first, the point zero. For this, the mercury and the water being poured in, as said above, the two branches must be left to communicate freely with the atmosphere, and the point where the index stops will be the point To prepare the instrument for use, an ad- sought, for that is the position which the and consequently ditional quantity of mercury is poured into float naturally takes when the branch Mb it by the aperture R, in order to be sure bears no more than the atmospheric presthat the instrument contains mercury at sure. If the two branches of the bent tube On the other side, the effective pressure least to the height Mm. After this the were to contain nothing but mercury, it is screwbolt M is unscrewed, so that if there clear that the point corresponding to zero (p), in whatever manner it be expressed, happen to be too much mercury it may run in the rising branch would be at m, as the may be replaced by the weight of a column off. When this is done the screwbolt is re-mercury would in that case stand on a level mercury, that would produce the same If then h be placed, and an additional quantity of water in the two branches. Instead of that, the pressure on the basis b. is also poured through R into the reservoir mercury in the branch M supports a certain the height of that column, which it is easy FG, and, should there be too much, it also weight of water, that is to say, the weight to calculate, we shall have runs off through the cock E. Then the in- of the column EM; it will consequently and the equation of equilibrium will thus be w-p= gobh; strument is put in communication with the tend to descend in that branch and to rise boiler. The steam, arriving through the tube in the other. However, if the float is made C in the upper part of the reservoir FG, to weigh as much as the column of water, presses on the water by virtue of its elastic the level will remain the same as if there or force; it consequently presses the mercury were only mercury in both the branches. down in the branch mb which is open at the top, The other extreme point of the scale must until the weight of the mercury, thus raised, afterwards be marked. Let be the presis equal to the pressure of the steam issuing sure we want to equilibrate; supposing the x = h x = h x 0.51913. from the boiler. A float borne on the sur-equlibrium established, let a be the height face of the mercury, at the point m, rises in at which, by virtue of that same pressure The height h of a column of mercury, proportion as that surface in the tube; and an, the mercury will stand above its natural which may represent a given pressure, is index suspended to a thread which passes level in the branch m. The mercury hav-easily found; for we know that a column over a communication-pulleyp, falls between ing risen in the branch m to the height x, mercury, one inch high, presses on its the two tubes in proportion as the mercury it must have fallen by an equal quantity in basis at the rate of 0.4948 lb. per square rises in the branch bm, and shows upon a the other branch; for the mercury added inch. The height of any other column graduated scale the variations that occur in on the one side can only proceed from the level of the mercury in the different what has been taken off on the other. The experiments. Supposing the length of the mercury in the branch M will therefore at instrument from M to b be 6 feet, or 78 the same time be at the point x', and the 70 inches, the ascending column may, if neces- whole part of that branch from the point x' sary, contain 156 inches of mercury; and to the point M will be filled by the water × 1 =141.47; 0.4948 as a column of 156 inches of mercury from the reservoir. If through the point x' so, that by this value of h, x will be with a basis of 1 square inch weighs about we draw an horizontal plane, the mercury=141.47 in. x 0.51913 = 6 ft. 14 in.; 80 lbs., such a column may serve to meas- which is under that plane will equilibrate it- that is to say, that to correspond to an ef ure an effective pressure amounting to 80 self in two branches; we have therefore fective pressure of 70 lbs., the height of lbs. per square inch. nothing to do with it, and need only con- the mercury must be 6 feet 1 inches. The reservoir FG is a cylinder 3 inches sider the conditions of equilibrium for those The same calculation is applicable to in diameter and 6 inches high. The use parts which are above the plane in the two any intermediate point that may be sought, of the water it contains is to keep the branches. Now, we have on the one side but it would be unnecessary trouble; for, branch Mb constantly full of water, in pro- the pressure more the weight of a col- knowing the point corresponding to zero, portion as the mercury descends in that umn of wate rhigh Mr=r; and on the other and that which corresponds to the maxibranch. This is the reason why that re-side, we have a column of mercury high mum pressure of the instrument, we have servoir is a great deal larger than the tube, 2x more the weight of the atmosphere. P only to divide the interval into equal parts, and its capacity is calculated so as to be being thew eight of the column of mercury, and the scale will be suitably graduated, able, in case of need, to fill the whole P' that of the column of water, and p that of having seen that the general value of x debranch. If this precaution were to be the atmosphere, we shall have, there being pends solely on the corresponding value of omitted, the water formed by condensation an equilibrium, h, and is proportional to it. in the instrument during the experiment p+P P' + ≈, or P = P' + (@. - p). would fall in the tube, which being very 11 p), which is the surplus of the real narrow, having, for instance, no more than pressure of the steam over the atmospheric one-half square inch area, the water would pressure, is called the effective pressure; of may thus be proportionably calculated. If, in. lbs. = = in. in. This mercurial gauge being once constructed and graduated, whenever any doubt may be entertained in regard to the pressure of an engine, nothing more is ne cessary than to bring it under the instrument, and by that means the pressure may be ascertained, in whatever state the valve may be at the time, whether blowing or not. is generated too much. The valve will §. Of the pressure of the Steam in Lo-pressing on the spring, and consequently When we make use of the mercurial gauge to discover the pressure during an experiment, attention must be given to a circumstance we are going to describe. If, the valve once regulated, the engine were to keep an equal pressure of steam during its whole journey, nothing more would be wanting than to try it once for all before starting. Having fixed the valve at the point at which we wish to work, the engine might be brought under the instrument; and the pressure being determined that corresponds to that point, provided no other alteration be made to the spring-balance of the valve, the pressure of the engine for every instant of the journey would be known. When the steam, in escaping, raises the valve to a given height, the greater the balance-lever is, the more the index will be displaced on the scale, and consequently, the greater will be the increase of tension of the spring; thus, in engines with a long lever, the augmentation of the pressure will be, cæteris paribus, more considerable than in those where the lever is shorter. same degrees through which it rose during the work, and by observing at the same time the mercurial gauge, we find for each of those degrees the corresponding pressure. That is the means we employed in our experiments. We brought successively under the instrument all the engines we had made use of, and for each of them, as they all differ in some point from one another, we determined the corresponding degrees of the mercurial gauge with the divisions of the spring-balance. RAILROAD TO CINCINNATI.-The following from the Charleston Courier of Thursday last, should incite our citizens to meet and send delegates to the Knoxville Con vention. formed that General Hayne, Chairman of The Charleston Courier-"We are inthe Commissioners eharged with the direction of the survey of a route for the proposed road, left the city yesterday morning by the railroad, for the mountains, where Captain Williams and his brigade of engineers are now engaged in making the sur veys. We also understand that Lieutenant Colcock, late of the army, who has just reroad from Branchville to Columbia, has turned from surveying the route of a rail been engaged by the Commissioners as an Assistant Engineer, and will proceed immediately to the mountains to join Captain Williams. Colonel Brisbane, also, who re turned from the Florida campaign the day before yesterday, will, we understand, engage in the work as soon as he can make the necessary arrangements. Of the services of Col. Gadsden, the Commissioners have been deprived by his military engagements in Florida. It is still hoped, however, that he may be able to join the Commissioners in time to give them the benefit of his judgment and experience at the meeting to be held at Flat Rock on the 20th June, or, at all events, that he will be able to attend the Knoxville Convention, on the 4th This increase of pressure in locomotive July, as one of the delegates from this city. engines, when they meet obstacles that In consequence of the information given by compel them to diminish their velocity, gives Gen. Hayne to the meeting of citizens on the engines with long valve-levers consid- Saturday last, of the astonishing performerable advantage over those with short ance of locomotive engines on the Baltilevers, whenever it is necessary to ascend stated in the public prints) acclivitiss of upmore and Ohio Railroad-overcoming (as an inclined plane. This advantage, it is wards of 200 feet-it has been determined true, is only gained by submitting the ento request some of our delegates to proceed gine to a higher pressure, and might also to Baltimore, to obtain the necessary infor be acquired with short lever engines by mation to be laid before the Convention at lowering the screw of the spring-balance, Knoxville, on the 4th July. We believe so as to increase the pressure in the boiler that one or two of the gentlemen composing in the same proportion; but the fact it-the delegation, have consented to perform self would evidently seem the proof of a have no doubt that others will unite in it, this important and interesting duty, and we superior working, and would even be in- if it should be deemed necessary. explicable, were we to look upon the pressure as never passing 50 lbs. It is thus that many persons calculate, whether or not use has been made of the mercurial gauge. When they have found We shall soon see that the ATLAS engine, which has a short lever, with a valve of 24 that an engine lifts up its valve exactly at 50 lbs. effective pressure per square inch, inches diameter, is able, while overcoming that very moment the valve is considered difficult obstacles, to raise its pressure from as giving a free egress to the steam, and it 53 lbs. to 56 lbs.; and that the FURY enis concluded thence that the steam will gine, which has a long lever, with a valve never rise above 50 lbs., unless the valve of 3 inches in diameter, is able, in the undergoes an alteration. same circumstances, to raise its pressure Experience, however, proves that this reasoning is false. from 53 lbs. to 621⁄2 lbs. These variations If we observe a locomotive engine with in the pressure depend, in each engine, in some attention, we shall very soon see that the first place, on the augmentation of the nothing is more variable than the pressure resistance created by the obstacle or the of steam in its boiler, although the valve diminution of the speed; and, in the sehas undergone no alteration. If the engine cond place, on the dimensions of the valves, runs rapidly with a moderate train, and levers, and balances, and the evaporating comes to a slight inclination of the road, power, that is to say, the quantity of steam however small that inclination may be, it generated by the engine. immediately produces a considerable increase of traction, because the gravity of the whole mass on the inclined plane becomes an additional resistance for the engine; and the effect of this increase of traction will be so much the more perceptible on the engine, the less the resistance was which the train offered when on the level parts of the road. It is thus that a load of one ton, which on a level road requires a traction of 8 lbs. only, presents nearly four times as much if it has to ascend an aclivity of the gravity of one ton or 22.40 lbs. on that inclination being 22.40 lbs. The consequence of that sudden increase of resistance is therefore that the engine, as soon as it arrives at the foot of the inclined plane, must diminish consider- The variations in the pressure which we ably its velocity. Supposing that in its have just montioned, take place while the preceding course it spent 480 cylinders of engine is travelling, that is to say, while it steam per minute, and in consequence of is separated from the mercurial gauge. the accidental obstacle it must overcome, Therefore, if an engine has been working it is obliged to reduce its velocity to one-in a given circumstance, or with a known third of what it was before, it will evident-load, and that we want to ascertain at what ly spend no more than 160 cylinders per pressure it was then working, we must minute; nevertheless, the fire violently write down exactly, during the experiment, excited by the preceding course will con- the degrees successively inscribed on the tinue to generate the same quantity. That balance; then, when the engine has left off steam, it is true, will be spent at a greater working, we bring it under the mercurial pressure; but experience shows that the gauge, and by animating the fire sufficiently surplus of pressure does not balance what to make the balance repase through all the 2240 The following interesting article on iron railroads in France, is extracted from the Journal de l Industriel et du Capitaliste: "Three grand undertakings especially occupy at this moment the attention of speculators, namely, iron railroads from Paris to Rouen and the sea, from Paris to Orleahs, and from Paris to Lille. Several lines have been proposed to join Paris to Rouen and the sea. The line surveyed by the administration passes by the side of Pontoise, traverses Gisors, goes from thence to the Bosc-le-Hard, and from that point proceeds on the right by the valley of la Saye to the Dieppe, and from the same point on the left to Havre. A branch pass. ing by, Blainville would reach Rouen neat |