the selection of what he calls facts, brought forward to elucidate his various reasonings; they are simply not facts, and there is more or less error in all of them; his want of practical engineering knowledge has led him into many ridiculous fallacies, and he has certainly proved himself incapable of comprehending what he has studied. I here allude to the "law of the squares" to note that I have not in any way questioned the truth of that law. I am fully content to leave that matter between Mr. Hoseason and the philosophers he has quoted. I have said that the required horse power is as the “cubes of the velocities," a law that has been confirmed by a very extensive practice, and before I have done I shall in many instances prove its correctness. I have not misquoted Mr. Hoseason in any way. I merely drew attention to the fact that when applying the law of the squares to the case of the Phoenix (p. 263,) he stated the square of 9 to be nearly double that of 7 (!) and as an inference was drawn therefrom, I intended it to show the loose manner in which his 66 points" are proved, and which is neither Russell's nor Lardner's way of doing such things, but all his own. Mr. Hoseason says, "that he left entirely untouched the question of what horse power ought to be placed in a vessel, in consequence of the increased resistance of the water, as it was not, from the line of argument he had adopted, the subject under discussion, &c., &c." No! He advocates throughout his letters "the economic use of fuel by the expansion of steam," and dwells upon the small ratio in which the velocity of the ship, and of course the power, decreases with the reduction of a moiety in the consumption of coals. This is his argument, which, though most verbose, contains some truth-some corn, but mixed up with an immoderate quantity of chaff. This granted, it does not appear to me what necessity there is for entering at all upon the question of the resistance of fluids as an abstract question. We have to ascertain what is the ratio of the power or force necessary to drive a given body through water at a given velocity; and it further appears to me, that must be determined by experiment alone, not made upon models in a horse trough, or other convenient place, nor upon one or two vessels, but upon many ships of different forms and scantlings. When I tell him that the "law of the cubes" has been proved by experiments upon more than 200 steam-vessels of varying forms, weights, and powers, this latter being accurately noted by the indicator, (and which power governs and controls all he has argued for,) during a period embracing a practice of 20 years, he ought to be thankful for the information, and certainly courteous enough to withdraw the appellations of "blockhead"* and charlatan, otherwise I must come before you in propria persona, and appeal to the profession for their decision as to which of us has the greatest claim to them. And now a word about the philosophers. I know something of Lardner, and have the honour of personal acquaintance with Russell, but have not disputed anything they have written; that has been done by Mr. Hoseason, who asserts that they differ in their theories; but this I do know, that they have the highest respect for experimental research. If the law of the cubes is not to be found in any of their books, all I can say is, that it ought to be, and I shall take the earliest opportunity to bring the matter under the notice of the latter individual. Mr. Hoseason is disingenuous: I was not so absurd as to credit him with the discovery of expansion. I wish to draw the line distinctly where we particularly disagree, and it is this-I say that the whole tone and tenor of his writing would lead a casual or uninformed reader to suppose that he was in advance of the times as to the practical application of * I am not so illiberal as to suppose that any one out of the profession cannot, by study and application, soon master the theory of the steam engine; but on the other hand, it must be allowed, that such an individual, be he ever so talented, cannot be expected to match those who have for years devoted their undivided attention to one object. The amateur is crude in his ideas, wanting experience to temper his knowledge. This is illustrated daily. During our last session of the Civil Engineers, one of the most able and talented officers in the navy made an absurd proposition relative to some fitment for her Majesty's vessels. Respect for the veteran alone smothered the cachinnatory movement that was ready to follow. Again, there is that "satisfactory" affair at Chatham, of which you have more than once so good-naturedly spoken, and the letters now under my notice are instances in point. They are all noble fellows, but a little out of their line, which should be that of battle. ON THE WORKING OF STEAM EXPANSIVELY. the theory of expansion, a very different thing; whereas I am clearly of opinion, had he never existed, that science, both in its theory and practice, would have been just where it is at present. Perhaps its practice would have slightly advanced, because in advocating truth he has mixed up so much that is untrue, and so much that is purely personal, he has produced scepticism where none existed previously. Mr. Otway's experiments in the Echo were right in theory, but failed for the precise reasons given in the previous note. He raised his steam to one atmosphere, not two, (see p. 124,) and the engine was "fitted with expansion gear." Now, this is what has been done in the private marine for years past, with this slight exception, that the boilers there used Occupy (for like powers) just one-third the cubic space of those of the Echo, with about threefifths the weight, having the capability of producing double the quantity of steam. If any man's theory states (and I am not aware of anything of the kind) that there is no more economy in the expansion of high than in low steam, it is undoubtedly wrong. That great controller of all theories, practice, is daily giving us proofs of this. The Great Britain appears to me particularly a case in point on the one side; she is worked under a pressure of 2 or 3 lbs. per square inch only, and expanding in the cylinder fivesixths of the whole stroke; therefore if any great economy attended this plan we should have it here. Allow me to refer Mr. H. to an article of mine on this subject, published in the Civil Engineer, vol. 6, page 80, where he will find a detailed table showing what should be the consumption of fuel and speed of that vessel with various powers and expansions. I have only carried the calculation to an expansion of four-sixths of the stroke, but let us take that and he will find that her expenditure per day should be about 34 tons, and her velocity about 9 miles per hour. Now, let us turn to this Magazine, No. 1161, page 308. We find that she has really consumed 63 tons per day! (although expanding five-sixths of the stroke only), which "G. S." states should give upwards of 900 horse power, and is correct, as will be seen by my table, published some months before the 357 I am Great Britain reached the sea. I have not been able to find any pas- 66 And here, sir, we have one of those exploded heresies for which Mr. Hoseason seems so famous-power has no strict relation to tonnage. How many vessels are at this moment in existence which have been considerably increased in tonnage and in speed with a less power? I can name at least twenty such of all classes and forms; the Alecto might be increased 50, or perhaps 100 tons in burthen, her speed be increased, and in every way made thereby a better manof-war than at present; and this is no mere fancy, but what every day's practice assures us. I merely stated a fact in saying it was recently a rule at Woolwich Dockyard, that the maximum safety-valve pressures should be 5 lb. per square inch. I may here add, that I have handled an indicator before such a thing was known in the Government service, and certainly many years before it knew an "Inspector of Steam Machinery;" and more especially still, that I have now before me a book containing upwards of 600 diagrams, taken under every conceivable circumstance of expansion, &c. I have no more occasion to go there for information than to apply to Mr. Hoseason for a lesson on composition. This rule was certainly no reason why engines should not be fitted with expansion gear; many of them were so, but what was its use? Mr. Hoseason's own testimony assures us it was not likely to be used half an hour! And what an apology is offered for so restrictive a regulation? "Because a higher, and therefore a more advantageous pressure was deemed objectionable at the period," &c. &c. In the name of all that is reasonable, if this increased pressure was advantageous, how could it be considered objectionable? Oh! Mr. Hoseason, you have yet much to learn as an amateur engineer: for your character and knowledge as a seaman I have a high respect.* Having now replied to every part of Mr. H.'s letter in No. 1162 that I think worthy of notice, I will turn my attention to the epistles addressed to Sir W. Parker and Sir G. Hammond, all of which, it is said, is not before us. Then, pray let us have it, and if like what we have, it will not be difficult to prove sufficient fallacy, false reasoning and data, to consign it at once to the "tomb of the Capulets;" but in these busy times this must be reserved for another week. I am, sir, your obedient servant, November 20, 1845. ON THE CONSTRUCTION AND USE OF GAS METERS. BY ALEXANDER ANGUS CROLL, ASSOC. INST. C. E. [From Proceedings of the Institution of Civil Engineers.] The use of gas, for the purpose of illumination, has now become so general in this country, and involves so much capital in its production and distribution, that any invention, by means of which gas can be more accurately measured than heretofore, becomes of importance. To honest consumers, an accurate measurement of the quantities used is a direct saving; for gas companies will, for their own protection, establish their scale of contract charges sufficiently high to cover all contingencies. Some idea may be given of the inefficacy of contracts, when it is stated, that warehouses, shops, &c., which were supplied with gas, for the purpose of illumination only, have been heated during the entire day from the ordinary burners, by merely substituting an iron cylinder for a glass chimney around the flame, so as to hide the * In my letter published in Number 1161, I comImitted an absurd error, and the most has been made of it. I stated the power of the Phoenix at 110 horses. I gave one engine only, as the diameter of cylinder and length of the stroke prove; but the ratios are the same with any power. I meant to show, that if a given power propelled that vessel 9k.ots, half that power wold produce 7.18 knots. light, and an inspector from the company might enter, without detecting the fraud. These and other uncertainties in the amount of gas used by the consumers must therefore be met, by a price high enough to remunerate the gas manufacturers, for the largest quantity which they believe may be used, under any circumstances. There is also no doubt, that various devices have been resorted to, by unprincipled consumers, to make their actual consumption appear considerably less than it really was, and thus a large quantity of the gas produced was not accounted for; but the manufacturers were compelled to divide the cost of it among all the consumers, and to make a proportioually high scale of prices. The fair consumer was thus not only made to pay for his own consumption, but to contribute towards that of his dishonest neighbours. The public therefore has an immediate interest in the exact measurement of gas. But if it be important to the consumers of gas, that it should be accurately measured, how much more must it concern the gas companies! To them the subject is one of extreme interest. It is well known that es much as from 30 to 40 per cent. of the whole quantity of gas produced is sometimes unaccounted for, and this great and positive loss has generally been attributed to leakage. That there is a certain constant amount of leakage through the pores of the metal, of which the mains and pipes are composed, is undeniable. The fact of such leakage is proved, by the saturation of the ground in which the mains are imbedded, though it would appear to have been somewhat hastily assumed, that such saturation would furnish a complete explanation of the whole of the known loss. The erroneous character of this opinion can be readily demonstrated by experiment. The most minute jet of gas can be detected by the smell; for instance, any escape of gas which can scarcely be discovered by its igniting upon the application of fire to the spot, is instantly perceived by the offensive odour. In the author's own house a very small escape of gas took place. This was so offensive, that its continuance would have rendered the room uninhabitable; but when estimated by the meter, it was found to be only one per cent. Further, escapes of gas in the streets have been detected by the smell, which when traced, were found to be incredibly small, when the nuisance they had occasioned was taken into consideration. These facts show, that it is impossible to account for even 5 per cent., instead of upwards of 30 per cent., of the ascertained loss, which is the utmost allowance to be made for loss from bad joints and porous metal in the mains. ON THE CONSTRUCTION AND USE OF GAS METERS. Practical observations, made in the performance of his professional duties, as superintendent of gas-works, have convinced the author, independently of theory, that such an amount of leakage is impossible; for if even 5 per cent. of loss really occurred in that way, the streets, through which the gas passed, would be absolutely intolerable. The amount of gass daily distributed from the works of the Chartered Gas Company alone may be taken at about 2,703,000 cubic feet; the loss of 30 per cent. upon that quantity would occasion 810,000 cubic feet of caburetted hydrogen to be set free daily in a comparatively limited district of the streets of London. It may be objected, that the gas escaping in the soil becomes decomposed, and that therefore no smell is observed; but this hypothesis is inadmissible, as in that case, the hydrogen would be formed into water, and the carbon would be deposited in the soil; therefore the quantity, by weight, annually left in the soil, from the supposed escape of 30 per cent., would be upwards of 3,000 tons. This is from the works of one company only; and if we consider the enormous ad. ditional quantity that would be produced from the other ten metropolitan companies, we cannot avoid pronouncing it to be utterly impossible. In the course of a tour of inspection made recently, through some of the principal gasworks of Manchester and Scotland, the author found, that there was in fact very little, if any practical loss of gas; but that it was nearly all accounted for. Almost all that was made by the companies being conveyed to, and paid for, by the consumers. There was, however, both in Manchester and Scotland, the same appearance of saturation in the ground, through which the mains passed, as in London. The metal of which those mains was composed was identical, and yet the Manchester and Scotch companies were paid for fully 25 per cent. of gas which in London was totally unaccounted for, and was wasted. It could not be doubted, that this advantage was obtained, by the whole of the gas being consumed by meter, under a judicious system of inspection. It must therefore be concluded, that the great loss of gas in London may be attributed to surreptitious consumption. The author's experience has furnished him with numerous instances, in which persons have been detected in the use of contrivances, to consume more gas than their meters indicated. In one case, a publican was suspected of some proceeding of this kind; but the gas company's inspectors could never detect anything wrong. The meter, which 359 was placed in a cellar, always indicated an extremely small consumption, and the publican was anxious to explain the exertions which he continually made to economise gas. Still the officers were not satisfied; but whenever they went to the premises, they could never obtain immediate admission to inspect the meter. There was always some special reason why they should call again in an hour, or the next day, though at their regular and anticipated quarterly visits none of these delays took place. An observation satisfied them, that more gas was consumed on the premises than was accounted for. At last, by stratagem, the inspector obtained admission to the cellar without any previous notice, and he found that the pipes had been unscrewed from the meter, and were connected together by means of a straight tube, and thus about two-thirds of the estimated consumption for that house was an absolute loss to the company. This case was the more remarkable, on account of the consumer being a leading member of a society for the prevention of fraud. In other cases either a bladder was used, or what was termed "a jerry," passed behind the meter, to connect the service-pipe with the fittings, without any communication with the meter. The ordinary wet meter is necessarily placed in the basement, in order to receive the water which, rising as vapour out of the meter, is condensed in the fittings. The meter is therefore almost always in a dark cellar or an obscure corner, and in some instances fraudulent methods have actually been in existence without detection, during the inspection of the company's officers. The extent to which these practices have been discovered, and the facilities which are afforded to the dishonest portion of the community, for rendering the water meter ineffectual, together with the excess of consumption by the contract consumers, leaves no doubt that they prevail so widely as fully to account for the whole loss, hitherto attributed to leakage. It will be obvious, that by the method of measuring gas by wet meters, placed in dark cellars and obscure corners, the gas companies must depend upon the vigilance of their inspectors, to an extent which is neither wholesome for the servant, nor secure for the employer. The introduction of a good meter has become therefore extremely desirable, and that which is the joint invention of Mr. Richards and the author, will, it is believed, prove a remedy for many of the evils which have been complained of. It can be placed in any position, even in the most conspicuous situations, and admits of precautions and checks, by which all surreptitious consumption of gas may entirely be prevented. The inspectors of the gas companies may thus obtain an exact knowledge of the consumption for each house, and the great saving effected, by bringing the extra quantity, of more than 30 per cent. of gas, into the estimate, will enable the manufacturers to lower their prices with profit to themselves, which will extend and increase the use of their production. It is well known that the water meter, invented by Clegg, and improved by Crossley, is substantially the same as that now generally in use. It is ingeniously constructed for measuring gas, and with proper inspection, in the hands of honest people, and of those who do not understand the art of disarranging its water level, it is a sufficiently accurate instrument. But there are the numerous difficulties, before alluded to, in the way of complete inspection, and unfortunately there are too many persons who understand the methods of rendering this meter inoperative, and who do not scruple to adopt such means of defrauding the manufacturers of gas. The action of the water gas-meter is generally understood. The gas is introduced at a central opening of the measuring drum, which is sealed with water; the pressure is exerted upon the surface of the water, and the diagonal divisions of the revolving wheel, which is the measuring chamber of the watermeter. The revolutions of the wheel, caused by the passing of the gas, are shown by the index. Now the effect of this meter can be easily evaded by various methods. The correctness of its measurement depends entirely upon the water in the meter being kept at the proper height; thus, for instance, if the case of the meter be tilted forward to an angle of from 5° to 13° (according to its construction), and a proportion of the water drawn off, so as to unseal the outlet of the measuring chamber, the gas passes through it without affecting the index, and without being registered at all. This is constantly done, and to an extent of which gas companies are little aware. Whenever the practice has been detected, the parties defrauding have attributed it to accident, and unfortunately the companies have no means of proving the design of thus surreptitiously obtaining gas. During the winter, the water contained in the wet meter is sometimes frozen; and then it is necessary, in order to enable the gas to pass through to the fittings, that the meter should be removed. The bad example of avoiding the measurement of the gas, until a fresh meter can be substituted, is thus set by the company itself. The number of new meters required on such occasions is so great, that a considerable period often elapses, before the frozen meter can be replaced. . To meet these admitted evils, various kinds of dry meters have been at different times invented; but hitherto they have been open to such serious objections as to prevent the general adoption of them in practice. The first machine of any importance was that of the Dry Meter Company. The material of which the measuring chamber of that meter was formed, was leather, which has been found liable to several objections. If the meter is used only occasionally, at intervals, the action of the gas upon the leather produces considerable contraction, and causes a registration of an increased proportion against the consumer. On the other hand, when the meter is in constant use, the leather is expanded, whereby more gas passes into consumption, than is marked by the index. This of course operated unfairly against the manufacturer of gas. Then the facilities it also afforded to the fraudulent, and the perpetual sudden changing of the valve to and fro, in its opening and collapsing, producing an unsteady flame, created a prejudice against its use, wherever a clear and steady light was required. These imperfections have therefore rendered this meter obsolete. The next dry meter was introduced by Sullivan; although of a different construction, it was formed upon the same principles, of the same material, and was subject to precisely the same evils as regarded the leather and the unsteadiness. This meter likewise never came into general use. The only other dry meter of sufficient importance to be mentioned, is that constructed by Defries. In this instrument, each of the three measuring chambers of which it is composed is separated from the others by a flexible partition formed of leather, partially defended from the chemical action of the gas by metal plates. This flexible partition is expanded by the pressure of the gas, and in the alternate expansion and contraction it forms a cone. Now as a cone is one-third part of a cube, one-third part of the surface only is available to the pressure of the gas. Independently of the loss of power thus occasioned, a further loss arises from the sides of the flexible partition being fixed, and the centre only being moveable, and registering by its motion the gas consumed. Further, if where the leather is attached to the sides of the case, there be a play of th of an inch between the plates and the line of attachment of the leather, in the backward and forward motion, it passes through 4th of an inch; thus, when by use and exposure to the atmospheric air the leather has contracted only 2nd of an inch, then in its motion it passes through this th part of an inch, the effect of which is, that the measuring chamber is diminished by this th of an inch, |