is by the use of the float. This is understood to have been entirely successful in the low-pressure boiler, the float being applied to raise a valve connecting a reservoir of water with the boiler to be supplied. A selffeeding apparatus in which a float was used was proposed by Mr. Charles Potts, who exhibited to the Franklin Institute a very neat working model, in which a glass boiler was kept at nearly a constant level by this method. Its application is most difficult in the case of a small high-pressure boiler with interior flues. Engineers differ very much in the amount of confidence which is to be placed in the float: those who have seen it in operation in the large boiler of a low-pressure engine give it implicit confidence; others who have tried it in the small high-pressure boiler, consider its action too uncertain to answer a good purpose, even when in its best form. If the objections to the float are not valid, and we apprehend that they are only partially so, the real difficulty will be found to lie in general objections to all self-regulating apparatus. This obviously is one which is liable to get out of order, since it communicates between the exterior and interior of a boiler, and hence must have a packed joint, liable when the stem is not in constant motion to become tight, and therefore beyond the power of the change of buoyancy in the float to move. 41. A most ingenious method of feeding boilers was patented in 1825, by Mr. Eve.‡ It consisted of a revolving-cock, bored in part through, and playing alternately into the boiler, and into a box of water. It was expected that this cock being placed at a proper level of the water within a boiler, would merely draw out and return water while this was at a due height, but when it sunk too low would draw out steam and return water. The difficulty of condensing the high steam§ drawn out, and of making the returned water flow out of the openings, seems to have rendered this, as well as other promising schemes of the same sort, abortive.|| Journal of the Franklin Institute, vol. vi. p. 42, and also p. 327, &c. where the apparatus is illustrated by a figure. †D. J. Barr on the explosion of steam-boilers. Jour. Frank. Inst. vol. vi. p. 335. Mr. Redfield objects to its use in steam-boat boilers. See Report to Secy. Tres. U. S. in Doc. H. R., No. 478, session 1831-2. Lond. Jour. of Arts, vol. xii. p. 230, Lond. Mech. Mag. vol. vii. p. 344, Rep. Pat. Invent. vol. iii. p. 70. A revolving-wheel for the same purpose has been patented by Mr. Jesse Fox. Jour. Frank. Inst. vol. x. p. 161. See also J. S. Williams' patent for supplying boilers with water. Jour, Frank. Inst. vol. vii. p. 183, which though different in action is liable to this objection, in even greater force. Walker's feeding-plug. Trans. Soc. Arts, &c., vol. L. Part I. p. 63. Sliding-valve and box. Lond, Mech. Mag. vol. xxi, p. 376. An attempt to obviate these objections, which was seen by some of the members of this Committee, was unsuccessful. Mr. Charles Potts has recently proposed a plan which is similar in principle. It will have to encounter the difficulty of the flow of water from moderately large openings when the pressure on the two ends of the column is the same, and the necessity for the alternate heating and cooling of the revolving-plug or chamber which acts as a feeder, and of at least a part of its contents. They agree entirely, however, with the Committee on Science and the Arts, that this principle merits further trial.** 42. The Committee are decidedly of opinion that no self-feeding apparatus has been, or is likely to be, invented which can be a substitute for the care of an engineer; and, indeed, they consider the carelessness which is liable to result from their use as a very serious, though not an insuperable, objection to them. 43. 2nd. Methods for ascertaining the level of the water in a boiler, or of giving notice when it falls to a certain level. The imperfection of the gauge-cocks in ordinary use has been often pointed out, and indeed is generally admitted. Originating in the very infancy of the art in Savery's engine, they remain at this day a stain upon its more mature age. At best,++ when the water is tranquil within a boiler, they only show, roughly, the position of the water-line; and when it is above the highest cock, or below the lowest, they fail entirely; and cannot be placed far apart without making their indications, within these limits, too rude even for practice. When a boiler is in action, particularly if it is small and contains high-pressure steam, the foaming is so considerable as to interfere with their use. In the report of experiments by this Committee, abundant evidence is to be found of this imperfection; as an example of which may be taken the case, where by raising the safetyvalve of the small experimental boiler, indications of water appeared at a gauge-cock, below which the hydrostatic level was known to be nearly two inches.‡‡ 44. The method of indicating the level of ¶ Journal of the Franklin Institute, May, 1836, vol. xvii. 302. p. ** Report on a "Plan of a new pump for feeding steam-boilers." Jour. Frank. Inst, vol. xviii. p. 3. 1836. From the remarks which follow, exclusive of the objection on the score of the effect of foaming, we must except the shifting gauge-cock of Mr. Philos. Tyler, described in Jour. Frank. Inst. vol. XV. p. 178. Report of Com. on Explosions, Part I. pp. 11, 12, &c. Jour. Frank. Inst. vol. xvii. pp. 9, 10. Peale on the height of water in boilers of locomotives. Jour. Frank. Inst. vol. viii. and Replies No. XXI. Potts on Explosions. Jour. Frank. Inst. vol. vi. p. 329. the water by a float is liable to all the objections urged against the feeding apparatus, depending for its action upon that instrument. It has not, however, except in very rare cases, been used in this country. An alarm float was tried by the Committee, which is not subject to the objection in regard to the stuffing-box, since it is entirely within the boiler. This is by no means a new device, though the particular arrangement was made by Mr. D. H. Mason for the Committee, and is figured and described in the first part of their report. This device is intended to allow the escape of a small jet of steam whenever the water rises above, or falls below, a determinate level.§ The alarm by the issue of steam through a trumpet tube, being only applicable to engines working at very low pressures, does not require special notice here. 45. With due care on the part of the engineer, and the Committee are of opinion that no substitute has yet been found for such eare, the glass tube affords the best means known to us, for observing the level of the water within a boiler. It seems strange that this excellent device which has stood the test both of experiment and of practice, has met with so limited a degree of favour. In the great progress made of late years, in the locomotive engine, it has been so clearly shown that engineers and their assistants can be induced to employ any machinery, the use of which is insisted upon, that the excuse of their indisposition to change should not be urged any longer. In this very case, in which the glass tube is probably more exposed to fracture than any other, it is prac tically used. The objection on the score of its breaking by unequal expansion and contraction of the glass, and of the metal with which it is connected, has been obviated, by passing the ends of the tube into stuffingboxes; that on the score of its breaking by shocks, by giving it great thickness; and that of its breaking by sudden variations of temperature, by using well annealed glass. The difficulty of the glass clouding when high *The hydrostat described in No. XXX. of replies is inadmissible, from the interior of the boiler being occupied by a second cylinder, leaving only an annular space for the production of steam. For the alarm-floats of J. L. Sullivan, Esq., see Silliman's Journal, vol. xx. p. 1. † See the alarm-float of Siebe. Lond. Jour, of Arts, vol. xiii. p. 273. The first of those known to the Committee. Report, pp. 14, 15, Plate 4, fig. A. Jour. Frank. Inst. vol. xvii. pp. 13, 14. It is exposed to a slight objection from steam. pressure acting to keep the disks upon the openings; these latter are, however, quite small, and the pressing surfaces of the disks may be regulated accordingly. The float described by Mr. Ewbank, Jour, Frank. Inst. vol. x. p. 7, is also referred to by the Committee as deserving a full trial. steam is used, by the action of the steam on the alkali, is got rid of by using green glass. The experiments which the Committee made on this apparatus were highly satifactory, and they confidently recommend its use to practical men.|| 46. 3rd. The danger resulting from a deficient supply of water, being produced by the undue heating of parts of a boiler, many means have been proposed for showing such an increase of temperature, before it attains a dangerous degree. The fusible plates ap. plied to the top of the boiler, may be intended to indicate the general temperature of the steam when saturated with moisture or not, or the local temperature resulting from the rising of hot and unsaturated steam, produced by unduly heated metal. In any case they will be exposed to pressure, though to less in the second case than in the first. The objections already urged, and derived from experiment, will apply to their use, in the ordinary way, in any one of these cases. Indeed, without this objection, it appears that as the source of danger is the heated metal, to this the indicator of temperature should be applied. 47. Various methods of indicating the temperature of a part or parts of a boiler have been contrived. One of the most simple is to apply the common thermometer, inserting the bulb and as much of the stem as is necessary, in a tube closed at one end and fastened into the boiler. The tube should contain mercury, through which the heat is conducted to the thermometer. Such a tube may be placed at or near the water line of the boiler, at the fire end of a flue, or in general at the place of a greatest exposure to heat from a deficiency of water, of which there will usually be one or more well determined, according to the form of the boiler. A mark upon the scale of the thermometer will show the temperature above which the metal must not be allowed to rise, either from an increased elastic force in the steam, or from a deficient supply of water. The fragility of the instrument, its inconvenient length or position in certain cases, and its not acting as an alarm, are the principal objections to its use. T 48. The expanding rods proposed by Mr. Cadwallader Evans, are ingenious; they give, however, not the local temperature of the boiler, but its general temperature, along the lines to which the rods are applied. A much more appropriate device is the application of fusible metal, proposed by the same gentle See the description of the tube water-gauge used by the Committee in the first part of their Report. Jour. Frank. Inst. vol. xvii. p. 10. Mech. Mag. vol. xxv. p. 88. For a detailed description of the mode of applying the thermometer, see the Report of Com, on Expl. Part I. pp. 7 and 8, and Jour. Frank. Inst. vol. xvii. pp. 5, 6. man.* This is intended to take the place of the ordinary fusible plate, and to avoid the difficulty originally existing, but since remedied,t of replacing the plate when it had fused. In the apparatus submitted to the Committee by their chairman, and subsequently made the object of experiment, the fusible metal is applied to the most exposed part of a boiler; it is so small in quantity, that it will serve to indicate a local temperature, while the motion which indicates its fusion is independent of the quantity of fusible metal. These instruments are intended respectively - to give notice when the steam, or the metal of the boiler, is exposed to a temperature much below that which would produce danger. Both of them, after giving an alarm, can be immediately restored to action, if the temperature within has been made to decrease.§ By very simple changes in the apparatus, the fusible metal might be applied to the boilers of locomotive engines. D Sir, In the report of the Select Committee of the Lords, to inquire whether any danger by fire is likely to arise from locomotive-engines on railroads, passing through narrow streets, the Committee say, "It does not, however, appear that as yet any plan has been devised, which could be described as being at once completely effectual, and, at the same time, not injurious to the operations of the engine." Mr. Stephenson, and other eminent engineers, who were on that occasion examined, stated to the Committee several plans which had been tried, by putting sieves in the chimney, both at top and bottom; but that the effect was materially to injure the draught, and consequently the speed of the engine. The following method (of which I enclose you a sketch) seems to me to obviate the objections which are inseparable from the contrivances hitherto tried, and which (if you *Communication to Com. on Explosions, No. XXII. of Replies, &c. Jour. Frank. Inst. vol. ix. February, 1832. Patented in May, 1834. See specification in Jour. Frank. Inst. vol. xiv. p. 391. The Committee prefer this to the apparatus acting by the expansion of mercury. † Hall's method of applying the fusible plate. Bulletin de la Soc. d'Encouragement, &c. Described in Jour. Frank. Inst. vol. x. p. 217. The apparatus devised by the Chairman of this Committee was made the subject of experiments, and, with them, described in Part I. of the Report of Com. on Expl. See Mech. Mag. vol. xxv. p. 118. consider it has sufficient merit) I shall be glad to see inserted in your Magazine. A A represents the hot-air chamber at the end of the boiler, into which the tubes from the fire-box lead, and from which springs the chimney D. C is the blastpipe, which conveys the waste steam by the pipes B B, from the cylinders into the chimney, causing a vacuum, and consequent draught. Now, my plan is, to stretch a wiregauze across the chimney from E to E, just below the orifice of the blast-pipe, and, at the same time, to widen the chimney at the same point, so that when the gauze is in its place, the free-air way shall equal, or, if necessary, surpass in area the rest of the chimney. When the gauze was tried at the bottom of the chimney, it was soon choked with cinders and dust, and speedily destroyed by the heat. In the present position this is obviated; and, if necessary, the more effectually to accomplish it, the chimney may be continued straight downwards for a short distance, in the direction of the dotted lines gg. When the gauze was placed at the top, it had to allow both the hot-air and steam to pass, and consequently any attempt to reduce its meshes to a size proper to stop small cinders was unavailing; besides, large ones being once drawn up beyond the orifice of the blast-pipe, by the direct force of the steam, acquired such velocity and momentum, that on their arrival at the wires, the cinders were broken into small pieces and forced through, and being quite hot till that moment were still capable of doing much damage; and the wires themselves were fully destroyed by the continual blows of such large cinders. Now, by placing the gauze as I recommend, only the hot-air will have to pass (the steam coming out above), consequently the meshes need not be so large; it will be out of the way of the heat, and at that period of their ascent, the cinders will not have acquired sufficient force to destroy the gauze. And by widening the chimney at that point, which can be done at a very trifling expense and no inconvenience, any area of draught way may be obtained. The cheapness and ease with which this may be applied to any engine, new or old, is not the least important consideration. I remain, Sir, Your obedient servant, 1, Cloisters, Temple, Jan. 27, 1837. Sir, I beg to state that the following was prepared before I saw No. 172. It is supposed that few persons now, who have thought on the subject, are not convinced of the necessity for, and utility of, longitudinal timbers under rails for railways, on all embankments, in the first instance, at any rate; and I think it will be ultimately found, that generally, throughout the entire length of any railway, it will be the cheapest, at first, to adopt, this apparently temporary plan, and for the time, let it be considered such. Where, however, there is no question respecting the firmness] of the ground for a sufficient length, and where slate, or stone, can be procured, these will be more permanent. I had partly prepared a paper on this] subject, before I left town last October. Mr. Vignoles, however, has now opened the field, and given data for observation. I would, therefore, submit that there is still room for reducing the cost of railways, and to do so, I consider will ultimately be advantageous to all par ties. It may just be noticed, that Mr. V.'s longitudinal wood sleeper has not so much bed, neither basit any thing like the weight per yard, as the stone blocks on the London and Birmingham line. However, with the transverse pieces of a proper strength, sufficient in number, and properly attached to the longitudinal timbers, their stability, by means of the ballast, or especially concrete, may be greatly increased. A bed of concrete may be laid under the timbers, but ballast only will be better for the upper part, as until the embankments have done settling, and the timbers and rails no longer require adjusting, it would not do to have the timbers surrounded by concrete. It is worthy of consideration, whether the advantage of long timber is such, as to justify its use, at an increase of cost, and whether home timber, cannot be made appropriate, either by Kyan.. izing, or carbonizing: a method for performing the latter, with uniformity and facility, may be easily contrived. In this way, supposing it desirable to have larger timber, it may be used at less cost. Round timber, for this purpose, will, it is thought, have some advantages over square (saving sawing, &c.) both when first bedded and in every subsequent adjustment, which from the settling of embankments, &c. may be rendered necessary, and will be equally steady when properly connected by the transverse pieces, and bedded in concrete or ballast. Any supposed inconvenience of short timber requiring many joints, will, it is thought, be more than counterbalanced by the facility of application and adjustment; and it is thought, a most effective and simple method of attaching the end of one longitudinal piece to another without any waste may be contrived. It is submitted, whether much smaller rails may not be sufficient, for not only where longitudinal timbers and continued state or stone platforms are laid, but even where blocks are so near each other as those at Chalk-farm, chairs not being required, and the rail being laid or bedded on the blocks, &c. to The form of rail that I would now propose is cylindrical. It is thought it may be under two inches in diameter. The length of the rails cannot now be specified, but if the rail be partly let into the wood (as in the sketch), or other material, on which it may be bedded, as this will give it lateral strength, it may be of a greater length than if only laid thereon. Such a rail as this, it is thought, may be fixed as firmly, and more steadily to the bed, than fany rail with flanges or chairs. I have tried rails one inch in diameter, for waggons carrying about two tons, which appear to answer well. Many fastenings may be contrived for this rail, but the best should have this property, that if a wheel be upon the rail its tendency should be to press upon the fastening; and if upon the fastening, its tendency should be to press upon the rail, and that both should have their bearing upon the sleepers or blocks; and allowance should be nade for expansion and contraction. It may be further said in reference to fastenings, that those whose tendency is to compress the wood, slate, or stone, are preferable to those whose tendency is to split the material. Again, those fastenings are the best which require the use of the simplest tools, and can be fixed, unfixed, and refixed with the greatest facility, and without any waste or injury to the materials, and without disturbing other portions of the work, should any part require to be taken up for any purpose whatever. The edge of the wheels for such a rail may, for ordinary purposes, be concave, a little greater in diameter than the convexity of the rail; but for ascending, if not descending inclined planes, it is proposed for trial, that the concave edge of the engine wheels may be such, or be capable of being made such, by an adjustment, so as to press, with any degree of force, against each side of the rail, so as to give the wheel hold of the rail. With respect to the diameter of the wheels, it is submitted whether they cannot, advantageously, be greatly increased, say, to at least 5ft. 3in. or 16 feet, or one pole, in circumference, or some definite portion of a mile. All wheels should be entirely encased, and a frame may be raised above them, from which carriages may be suspended all round them, before, behind, between, and on each side. In the accompanying engraving, A is a transverse section of the rail; B, the same of the longitudinal timber; C, the transverse tie; Ď D, concrete; E E, ballast. The radiating lines on the section of the rail, show that if each be alternately placed at top, the whole surface of the rail may be brought into use. Much more might be said on the above, but it would answer little purpose without experiment. I am, Sir, your obedient servant, |