ON THE CONSTRUCTION AND USE OF GAS METERS. over the whole diaphragm. Now since it measures merely a conical space, it must be evident that this loss of th of an inch over its surface very much lessens the measuring chamber. In cases where the meter has been some time at work, it is stated, that it has thus registered, against the consumer, as much as from 8 to 11 per cent. The reverse of this occurs when the meter has been some time in use, without any admission of air, and then the manufacturer incurs a loss. Each flexible partition consists of four triangular divisions, each of which is protected by a metal plate and between each division and all round the outer rim of the partition, where it is attached to the case of the meter, there is necessarily an uncovered surface of the leather, to allow the partition to move freely backwards and forwards, this leather is consequently liable to be acted upon by the gas. This circumstance must be an objection to every meter, in which the flexible material forms part of the measuring diaphragm. Croll and Richards' meter avoids these objections, which have hitherto prevented the general use of dry meters. The machine will be more readily understood, by imagining a steam engine measuring its steam, as it really does, in all cases. The steam enters the cylinder, from the boiler, on the top of the piston, forcing it through a certain space; the supply is cut off, and the action is reversed, the bulk of steam occupying the space through which the piston moves, is thus measured; for presuming the piston to be of a given area, and the distance through which it moves at every stroke, to be constant, it can readily be conceived how the actual quantity of steam employed could be indicated or calculated. The meter in question bears a strong resemblance to a double engine. It consists of a cylinder divided by a plate in the centre into two separate cylindrical compartments, which are closed at the opposite ends by metal discs; these metal discs serve the purpose of pistons, and they are kept in their places by a kind of universal joint, adapted to each; the space through which the discs move, and consequently the means of measurement, is governed by metal arms and rods, which space, when once adjusted, cannot vary. To avoid the friction attending a piston working in a cylinder, a band of leather is attached, which acts as a hinge and folds with the motion of the disc; this band is not instrumental, to any extent, in the measuring, so that if it were to contract or expand, the registering of the meter would not be affected, inasmuch as it would only decrease or increase the capacity of the hinge, the disc still being at liberty to move 361 through the required space; the leather is also distributed in such a manner, being curved, and bending only in one direction, that it prevents any wrinkles or creases from forming, and renders it, therefore, much more durable. The arrangements of the valves and arms are somewhat different to that of a steamengine, although similar in principle. Another advantage of this meter is the small amount of pressure which is required to work it. This valuable quality can be best appreciated by practical gas manufacturers. By means of this meter the gas companies possess an accurate measure of the quantities of gas actually consumed by each of their customers, and their inspectors have no longer to contend with the difficulties and the frauds above enumerated. Mr. CROLL explained, that the chief peculiarity of this meter consisted in the disc moving bodily forward, without having any portion of the periphery limited in its action by a hinge. The band of leather surrounding the disc, might be compared to the packing of the piston of a steam-engine, and any expansion or contraction that might take place, could not alter the capacity of the measuring chamber, or change the distance travelled by the disc. The leather was not liable to crack, as it was not worked backwards and forwards, but was always bent in the same direction. He considered this was an important improvement, as in almost all other dry meters, the flexible material acted as the hinge, at the same time that it formed part of the measuring chamber. He found, practically, that the action of the meter was very steady and that the measurement was accurate. About eleven hundred of these meters were now in use, although they had only been manufactured for the last nine months. Mr. DEFRIES said, there were some points of Mr. Croll's paper, with which he could not accord, although he perfectly agreed in the statement of the general deficiencies of the wet meters, and the facilities they afforded for fraud. Being aware of the objections against all meters with only two compartments, as being liable to cause oscillations of the lights, he had, in the construction of his meter, adopted three chambers, in order that its action, like that of a three-throw pump, might be continuous. In practice this was found to be the case, and at the Thames Tunnel, the House of Lords, and in many private establishments, where very large meters, made by him, were used, and their measurements were tested daily, none of the contraction, or expansion, of the leather hinges, or any alteration in the size of the chambers, had occurred. The leather used, was prepared expressly for the purpose, and he believed, that the theoretical objections, both to the use of leather hinges, and to the form of the chambers, were not well. founded; at all events, no ill effects had been found to result from either in a period of seven years, during which time, upwards of ten thousand meters had been made. He contended it must be evident, from the form and the arrangement of the chambers of his meter, that it would work correctly under a low pressure; indeed at less, he thought, than if the disc moved bodily forward; but that point could only be ascertained by actual comparative experiments. Mr. STEVENS had used all the kinds of meters extensively, and he certainly preferred that of Mr. Croll, with whose observations he accorded, relative to the wet meters, and he was of opinion, that it was desirable to obtain a meter that should not be subject to any variation in the dimensions of the chambers, to which, he apprehended, all of them would be to a certain extent liable while leather was used for any part. Mr. J. FAREY knew Mr. Clegg's wet meter well, and thought the principle on which it was constructed was so perfect, that it would be difficult for any dry meter to supersede it, provided the cases of wilful fraud were guarded against. All measuring instruments required care, and he apprehended, that the new meter would be in some degree liable to the objection of being tampered with, which had been urged against the wet meter. He thought the most serious objection to the wet meter, was its liability to freeze and to become useless in the winter. The meter with three chambers, appeared at first view, most likely to keep up an equal flow of gas, and he did not think the dimensions of the chambers would be subject to alter, so as materially to affect the capacity. The meters with two chambers, were somewhat on the principle of the diaphragm pump, patented by Benjamin Martin, nearly a century ago, but which did not succeed in water. The same kind of pump was more extensively used for the "Carcel" lamps, and in oil it was very durable; but he was of opinion, that when working in dry gas, the leather diaphragm would crack, unless it was prepared in a peculiar manner to resist this tendency. Captain W. S. MOORSOM said, that a point of much interest connected with the subject, was the leakage of the gas through the metal pipes. He understood the same effect had been observed, on the atmospheric rail way, where the leakage through that portion of the main which was composed of close pipes, was as great in proportion as in that part with the continuous valve. Mr. J. T. COOPER said, there could not be any doubt of the porosity of the ordinary metal pipes, so that the process of "endosmose and exosmose" occurred to a great extent, particularly with soft iron pipes. This subject had been discussed at length last session.* If harder iron, of a greater density, were used, there would be less porosity. He was astonished to hear the statement, relative to the leakage of the air through the metal of the pipes, in the main of the atmospheric railway; but with respect to the pipes in the streets, it was not surprising, that carburetted hydrogen gas, which was very volatile, should traverse the pores of soft iron. The method of exhibiting the "endos. mose and exosmose" process, by means of jars, covered with a sheet of India rubber, and filled with gases of various density, was well known to chemical students. Mr. FAREY believed that if the gas pipes were made from better materials, they would not be so porous as to be in any way prejudicial; but now, for the sake of a low price, they were cast from any sort of coarse bad iron, and they could scarcely be expected to be sound. Much also depended upon the method of casting them. If they were cast in moulds placed vertically, with fountain jets, the thickness of the pipes would be more uniform, and the metal would be less liable to be spongy. Mr. Lowe was of opinion, that Mr. Croll had estimated at too low a rate, the amount of leakage of gass from the station, the mains and the service pipes. He was aware of the difficulty of arriving at a correct estimate of the loss, from the different parts of so comprehensive a system as the lighting of a district; but he was anxious to remove any impression of the Gas Companies' sanctioning any attempt at incorrect measurement of the gas delivered for consumption, and he thought also, that although some flagrant cases of fraud, on the part of the consumer, had been detected, there was some little exaggeration in Mr. Croll's statement of the extent of such practices. Mr. Lowe was aware, that in some places extraordinary results were announced. For instance, at Rothesay, Isle of Bute, the engineer said, that he could account for every foot of gas that was made. He did not even allow the loss of 5 per cent., which it was generally admitted, not unfrequently leaked * Vide "Minutes of Proceedings," 1844, vol. iii. p. 307. ON THE CONSTRUCTION AND USE OF GAS METERS. away, by the defective joints of old gasometers. No allowance was made for the condensation in the mains, of the aqueous vapour, and other matter carried over by the gas, and which constantly occurred in all pipes. Mr. Lowe had made a careful examination of this point in a main of pipes, 18 inches in diameter and nearly a mile in length, which was laid from the Horseferry-road gas station to the Houses of Parliament, for the express purpose of lighting those buildings alone. At first it was observed, by the difference between the meter at the works and that at the House of Lords, that there was a leakage of about 150 feet per hour; there was not any perceptible smell at the surface of the ground, but when the pipes were laid bare, it was discovered that they had been badly laid and that there were many defective joints. The whole line was repaired and was apparently perfect, but still there was a certain amount of leakage. The same had been observed in the independent main from the gas works to the Penitentiary. During the daytime, when no gas was used, and the pressure was only ths inch, just to keep the main filled, the meter on the main at the gas works never stood still, but eventually indicated a certain amount of loss, which could only be the result of leakage from the pipes. Another source of loss, was that which arose from the destruction of the wroughtiron service pipes, by oxydation under ground. It had been asserted, that in opening the ground in the streets, it was not uncommon to find, that the whole of the metal of the service pipe was gone, and that the gas travelled through a tube of metallic oxyde, which had formed a sort of concrete, with the gravel in which the tube had been laid. Many kinds of artificial coating had been tried for protecting the service pipes from the action of the damp erth, but Mr. Lowe believed, that hitherto nothing effectual had been discovered. The wrought iron service pipes would, at present, last from three years to five years, after which new ones should be laid down. He was convinced, that more than 5 per cent. should be allowed for the leakage of the main alone, independent of all those other sources of loss which he had enumerated. Mr. Lowe did not think, that any of the meters registered with mathematical accuracy, the quantity of gas passing through them but he was of opinion, that if the water line of the wet meter was correctly maintained, that meter, in its actual improved state, was the most accurate. very hot, or very cold situations, dry meters were essential, as the evaporation of the In 363 water, or its freezing, would equally derange its action. The freezing could be obviated by dissolving in the water a little common salt, or some caustic potash (soaper's lees); but the evaporation could not be prevented. He thought, that when in good order, the dry meters would work under as light a pressure as the wet meters; but there was a possibility of the leather becoming rigid, if they remained any length of time inactive. The ratio of the amount of the leakage did not appear to follow the same rule, with respect to the diameter of the pipe, as did the quantity of gas passing along pipes of given diameters, under given pressures. Mr. CROLL did not think Mr. Lowe's arguments conclusive, against the position assumed in the paper. The case of the Rothesay gas works had not, alone, been considered, as many gas works accounted for within 8 per cent., of all that was sent out. The Manchester works had a deficiency of only 3 per cent. In a main of very large pipes, extending from the gas works situated at West Bromwich, to Birmingham, a distance of nearly seven miles, the amount of leakage was only from 7 to 8 per cent. The gas was sent along the main, under a pressure of about 3 inches, until it reached Birmingham, which was about 120 feet higher level than the works at West Bromwich. About 16,000 cubic feet of gas passed through the main per hour. Mr. Croll exhibited the discs and leather packing of his meter, detached from the case, and explained, that from the manner in which the leather was attached to the discs, whatever expansion or contraction occurred, no alteration could take place in the quantity of gas expelled by each forward motion of the disc; for the packing formed a bag all round, in which a certain quantity of gas lay stagnant, and whether that bulk was greater or less, no difference could be produced in the measurement. Mr. FAREY thought the rigidity of the leather would very probably impede the action of the dry meter, and that the unexpressed gas which remained in the bag, or packing, would probably become more dense, and thus more inequality of measurement would ensue. The wet meter was free from these objections. Mr. APSLEY PELLATT was a considerable consumer of gas, and he must be allowed to give his testimony in favour of the dry meters; he found, that in consequence of inattention to the water line in the wet meter, errors of measurement had repeatedly occurred, and constant annoyance had been experienced from their being frozen in water; but since he had, adopted the dry meter, a saving of nearly 15 per cent. had resulted. THE CONDENSED STEAM-VACUUM PRINCIPLE, PROVED TO BE THE ORIGINAL PATENT OF MR. S. CARSON, IN OPPOSITION TO THE CLAIMS OF MR. MALLETT AND MR. NASMYTH. BY HENRY DIRCKS, ESQ. At a time when the railway world is agitated with schemes of every mechanical variety for one kind or other of railway improvements, and the directories of the numerous lately projected companies have one system of propulsion after another offered to their notice as the safest, most economical and expeditious, it becomes an important duty to examine with care and settle with exactness the claims of those inventors whose plans offer the most reasonable prospect of ultimate success. The atmospheric principle of propulsion has afforded many interesting practical results in opposition to the preconceived opinions of not a few eminent railway engineers; first, as evidenced at Wormwood Scrubbs, where Messrs. Samuda's first experimental line of road was laid down; afterwards in the extension of the Dublin and Kingstown Railway, at Dalkey; and more recently at Croydon. The only great drawback to this principle appeared to arise from the unavoidable expense of producing the required vacuum by powerful stationary steam engines at comparatively short intervals. When Mr. James Nasmyth's patent for a steam-vacuum (sealed October 22, 1844,) was announced, his distinguished character as a most inventive and intelligent engineer, naturally contributed to raise expectation, that a principle at once so simple and economical as that proposed by him would, if anything could effect the object, prove the salvation of the atmospheric principle of railway propulsion. Instead of costly engines, and air-pumping machinery, the entire labour of obtaining the vacuum in the propulsion tube was to be performed by a communication with two or more vertical cylindrical boilers, or vessels of like construction; high pressure steam entering at one end was to blow out at the other the contained air, without employing any piston-for Mr. Nasmyth found the steam and air did not intermingle, at least not to any detrimental degree-and by means of a suitable condenser, using a pipe, or rose, a jet of cold water could be thrown in as formerly introduced for the old atmospheric steam engines. Then by opening suitable valves, the air rushing into these vacuous cylinders would exhaust the propulsion tube on the line of railway. Every one who heard of this mode of applying the condensed steam-vacuum principle, unhesitatingly avowed its excellent adaptation for the intended purpose. It would be singular if an invention so apparently obvious to any practical mechanic should escape being anticipated, and we can scarcely be surprised, therefore, in this instance to find it the case; a curious instance being afforded by the published papers of Robert Mallett, Esq., A.B., Memb. Inst. C.E., M.R.I.A., &c., which appeared in Mr.Weale's Quarterly Papers on Engineering, containing three communications by this gentleman, “Upon Improved Methods of Constructing and Working Atmospheric Railways.' They bear date Nov. 15, 1842, and will be found in the Mechanics' Magazine from 20th Sept. to 4th October last. It seems Mr. Mallett was consulted by parties interested, in reference to the subject of improving the means of obtaining the vacuum for use upon atmospheric railways, the latter part of the year 1842; and having first communicated his ideas, confidentially, to one party, he afterwards drew up a Memoir, sealed it, and deposited it in the Archives of the Royal Irish Academy, on the 13th of November, 1843, (one year after its composition,) Mr. Nasmyth's patent being specified the latter end of April, 1845. Mr. Mallett no sooner became acquainted with its purport, than at an early meeting of the Academy, on the 20th of May, 1845, he had his sealed packet opened in their presence, when it was found to contain three MSS., which it is presumed are those already alluded to as being since published. The inventions certainly appear identical, and so far, a remarkable coincidence is established. Mr. Nasmyth, in his patent represents two vacuum cylinders placed vertically; Mr. Mallett shows four placed horizontally; but in principle both are dependant on blowing out the air by the direct action of high pressure steam, and condensation afterwards, as Mr. Mallett says, by 66 water supplied to the condenser by a perforated pipe and stop valve." The only extraordinary part of the matter is, that Mr. Mallett should assert his priority in reference to Mr. Nasmyth, when THE CONDENSED STEAM-VACUUM PRINCIPLE, ETC. the latter had actually specified a patent claim, and which became public property nearly a month before anything was heard of Mr. Mallett's secreted memoirs; yet he speaks of them as being "published prior to the date of his (Mr. N.'s) patent"! However, I am now prepared to show, that neither of these esteemed and talented engineers has any just claim to priority of application of this, as Mr. Mallett designates it, generation and 66 condensation of steam in close vessels of suitable capacity." On February 5, 1840, a patent was granted to Mr. Samuel Carson, for improvements in apparatus for withdrawing air or vapour. Mr. Carson's object was to produce currents of air, either by a blast of air or steam; or by a vacuum produced by the condensation of steam. He describes various modes, some applicable to chimney tops, others to flues, others to the shafts of mines, and for other purposes. It will here suffice to state, that in his specification the following diagram is given as figure 8. F' and the patentee describes it as showing “another apparatus, constructed according to my invention, and is to be worked by a vacuum produced by the condensation of steam; f, is a shaft or pipe, in connection with a mine or house, or other place, from which it is desired to withdraw air. On the upper part is applied a valve opening upwards; g, is 365 a vessel into which the pipe f1 enters; consequently any air which passes from the pipe way f, will flow through f1, into the vessel g, and when steam is admitted into the vessel g, the air therein will be driven out at the opening and valves, h. The vessel is supplied with two pipes, one by which steam is allowed to flow into the vessel, g. I prefer to use high pressure steam, and to cut it off at such a position that in expanding it will fill the vessel, g, with atmospheric steam; but I do not confine myself thereto. "The other two pipes lead to a condenser, i, and there are stop-cocks on the steam pipe, and the pipe which leads to the condenser, which cocks are to be alternately opened and shut. Thus, supposing steam had been allowed to flow into the vessel, g, and was closed, the cock on the pipe leading to the condenser, i, would be opened, by which the steam would rush away and be condensed, and there would be a vacuum produced in the vessel, g, but that the valve on the passage opens, and air flows into and fills the vessel, g; the cock on the pipe to the condenser, i, would then be closed, and the cock on the steam pipe would be opened, by which steam would again flow into the vessel, g, and drive out the air therefrom by the air valve. And by this arrangement a very cheap apparatus for using steam as a means of withdrawing air will be obtained." And in conclusion, he says, "I claim the mode of constructing apparatus to be worked by steam and condensation, as described in respect to figure 8." This specification was enrolled 5th August, 1840. A more complete proof than this cannot be offered of the nullity of Messrs. Nasmyth and May's patent, or of the unsubstantiality of Mr. Mallett's claims, although his opinions are supported by Mr. Bergin, Dr. Robison, Ast. Royal, Armagh, Dr. Apjohn, T. C.D., and equally unquestionable authorities, their evidence in favour of this economic mode of effecting a rapid and complete vacuum, only affording most satisfactory evidence of Mr. Carson's just views, and the talent and ingenuity he has displayed. Had Mr. Carson confined his patent claim to a particular object, which he has not done, then indeed Mr. Nasmyth would still be entitled to the application |