Appendix that they have given rise to two questions of considerable interest, connected with the copyright of inventions. The first relates to Mr. Mallet's plan of storing the vacuum. Messrs. Clegg and Samuda, in the specification of their first patent, have these words, "If the trains are required to be started as frequently as possible, the engines are employed constantly exhausting the pipe; but if a longer period than is necessary to exhaust the pipe be required to elapse between starting the trains, the engines are employed IN THE INTERVAL to exhaust large vessels or reservoirs, whịch, when the train starts, are opened to the pipe to assist to obtain the vacuum therein, and to maintain it till the train has passed." Messrs. Clegg and Samuda say that this passage contains a complete anticipation of Mr. Mallet's plan, as disclosed in his Report, No. 1; and Mr. Pim takes the same view of the matter. Mr. Mallet, on the other hand, contends that "the sentence in the specification that proposes to use the engines to exhaust reservoirs, in the intervals between trains, under certain circumstances, was no publication of his invention for their constant and continuous use at all times, both during the intervals of trains and during their transit, or in circumstances where there were no intervals-in a word, FOR ABANDONING ALL EXHAUSTION OF THE MAIN DIRECTLY BY THE AIR - PUMP. We think Mr. Mallet entirely in the right, and are only surprised that a gentleman of Mr. Pim's keen penetration and strong judgment should not have instantly recognized the great difference there is between the two cases. (That Messrs. Clegg and Samuda should, as patentees, choose to confound them is natural enough.) The only idea common to the parties is that of storing up a vacuum, (which, as it happens, is new to neither;) but if the first suggestion of such a thing were to be held to comprehend and forestal all that can ever arise out of it, there would be an end to all proprietary value, in the application of scientific knowledge to useful purposes. Robert Mallet is no inventor in the sense only that James Watt is none; for both have only shown how to turn to a vast profitable account, a source of power of which all the world was previously well aware. The second question of right relates to the method of obtaining the vacuum by direct condensation of steam, described in Mr. Mallet's Memoir, No. 3. The date of this Memoir, is 15th November, 1842; and that Memoir was communicated, in confidence, to Mr. Pim and certain other parties, who are not accused of having violated that confidence. For the sake of greater security, Mr. Mallet deposited with the Royal Irish Academy, on the 13th November, 1843, a sealed packet, which, on being opened in presence of the Academy, on the 20th May, 1845, was found to contain three MSS., descriptive of Mr. Mallet's improvements in obtaining vacuum power on atmospheric railways; and these three MSS., we are led to infer, are precisely the same in substance as the three Memoirs now published. (We say "led to infer," because Mr. Mallet does not state as much in plain and distinct terms.) But, between the first date, 15th November, 1842, and the last, 20th May, 1845, Mr. James Nasmyth took out a patent for an improvement in atmospheric railways, which happens to be substantially the same with that which Mr. Mallet had taken so much pains to keep secret.* "The method of exhaustion by direct condensation of steam has been re-invented within a year or so, by Mr. Nasmyth, of Paticroft, near Manchester, who has patented an arrangement for the purpose, (sealed Oct. 22, 1844,) which differs in no essential particular from mine as described in my Report, No. 3, and published prior to the date of his patent."-Appendix, p. 66. Now, on this second question, our judgment must be as decidedly against Mr. Mallet, as in the previous instance it was in his favour. We think he must, on farther reflection, see the absolute necessity of retracting the assertion that his plan was published prior to the date of his (Mr. Nasmyth's) patent." There was no publication. On the contrary, Mr. Mallet did his utmost to prevent publication-to keep his plan as secret as pledges and sealed packets could make it. For anything that the public knew of Mr. Mallet's plan on the 22nd October, 1844, when Mr. Nasmyth's patent was sealed, it was all the same as if it had never existed. Nobody had, before the date of Mr. Nasmyth's patent, "pub For full details of this method see Mech. Mag, vol. xlii. p. 430. ATMOSPHERIC RAILWAYS BY DIRECT CONDENSATION OF STEAM. lished" what Mr. Nasmyth then disclosed to the public; and being the first to make it public, he is, in the eye of the law, the only "first and true inventor." Nor in the eye of the law alone; for this is a case in which law and common sense happen to be in excellent accordance. For, granted that Mr. Mallet invented the same thing before the date of Mr. Nasmyth's patent, but kept it secret, how can we be sure that he is the only person who is in that situation? Is it quite impossible that there should have been other prior inventors and other sealed packets? And are we in a case where verification is so difficult and simu 197 lation so easy, to open the door to all and sundry to come in and try their luck at this game of dormant pretensions? What title of discovery would be safe, if subjected to such an ordeal? Again, if those who impugn Mr. Nasmyth's title are not to be held bound by the principle of publicity, why should Mr. Nasmyth? Certainly, the date of Mr. Nasmyth's patent was not the actual date of his invention any more than the date attached to Mr. Mallet's Memoir, No. 3, was that on which the plan described in it first occurred to his mind. From what date, then, (supposing the fact of publication to be disregarded) Fig. 5. ought we to begin to reckon Mr. Nasmyth's title ? And from what Mr. Mallet's? To such questions as these it would clearly be vain to hope for any satisfactory answer. To depart from the principle of publicity is to get at once involved in inextricable obscurity and confusion. To adhere to it is not only a necessity arising out of the circumstances of the case, but a necessity enforced by the strongest considerations of public policy. The keeping of an invention secret which is calculated to add to the wealth or resources of a country, is as actual a public loss as if so much treasure of gold and silver were thrown into the sea; and to diminish as much as possible the number of such losses is, or ought to be, an object of must be allowed, that no one has more ably demonstrated its practicability and advantages than the author of the present paper. On the means of Producing Vacuum for the Atmospheric Railway by the Direct Action of Steam. With an example of six miles of railway main exhausted in one length. By Robert Mallet, Esq., A. B., Mem. Inst. C.E., M.R.I.A., &c. &c. (15th Nov. 1842.) In the case of vacuum procured for locomotive purposes by means of an airpump wrought by a steam-engine, it is plain that the engine can only be considered as a primary machine to produce a vacuum, the power resulting from which is again transferred to a second machine, the airpump, whose function it is to reproduce the vacuum whose resulting power is to be applied to effect locomotion. Hence, of the power of the coal, or theoretical power of the steam, there must be lost, that due to work these two complex machines themselves. The residue can alone be that available for locomotion. It therefore would appear, that if the generation and condensation of steam in close vessels of suitable capacity could be conveniently effected, its whole theoretic power, with some very small deductions, would be directly available in producing vacuum for locomotion. But besides this very general view, important practical considerations, especially relating to the conditions of working the atmospheric railway system, seem to be involved in the latter mode of obtaining the vacuum. It is admittedly of great value to be able to use the longest possible lengths of tube between station and station, and to be able to procure a vacuum in the largest length of tube with the greatest rapidity. On the existing method, any increased length of tube, or rapidity of exhaustion, can only be obtained by a proportional augmentation in the capacity of the airpump, and an equally proportionate increase of steam power; but as no means are as yet provided for using this power to advantage between the times of trains, and as steam must be always up in the engine boilers, any increase in the rapidity of exhaustion must be attended with a proportionate loss of fuel, beyond that only necessary to meet the increased demand for power. Now in further considering this new mode of producing vacuum by the direct application of steam, it will appear: 1st. That greater lengths of tube may be more rapidly exhausted than would probably be ever proposed to be attempted with the air-pump alone. 2nd. That such lengths of tube may be exhausted to a sufficient degree with great rapidity, and the tube discharged as the train advances. 3rd. That an economy of power, or in fuel, will result. 4th. That the apparatus may be so arranged that the whole of the steam generated between the trains shall be made available to produce vacuum. 5th. That the required apparatus will be more simple, and subject to less wear and tear, than an engine and air-pump of equal power, and certainly not more costly in original outlay. so as to econo 6th. That this method admits of combination with my other proposal for "storing the vacuum,' mize the whole power wasted between trains upon the present system. We will first, then, briefly describe the apparatus proposed being used, as designed for six miles of fifteen-inch tube. This consists generally of a system of boilers to generate steam, arranged upon a modification of the Cornish construction, and with peculiar adaptations for withdrawing the fires when steam is not demanded; of two sets of vessels wherein the vacuum is produced, and which I call "vacuum vessels," each consisting of two cylinders; and lastly, of a third vessel, called the condenser, in which the steam which has been generated in the boilers, and been blown into the vacuum vessels, expelling the air therefrom, is condensed, leaving them vacuous. The boilers are six in number; five are required to be in action at once, leaving one for cleaning; each of these is cylindrical, on the Cornish plan, but with a fire-place at each end; the flues meeting in the centre of the length, and with a large super-imposed steam-chest to contain a sufficient volume of steam to fill the vacuum vessels alternately with rapidity. Steam is to be produced in these boilers at 45 lbs. per square inch, above the atmosphere, and will blow off into the vacuum vessels, down to low pressure, or almost to atmospheric pressure. ATMOSPHERIC RAILWAYS BY DIRECT CONDENSATION OF STEAM. The construction of the boilers is such as to admit of the withdrawal of the fires from beneath all those in use, by a simultaneous movement, into a brick-arched vault or cavity, the supply of air and the chimney dampers being shut off by the same movement. The air within the cavity and boiler flues is thus almost immediately exhausted by the fires, of its oxygen, and replaced by carbonic oxide and acid gases and various inflammable products of the coal. The fuel thus ceases to burn, but remains hot, and smouldering, until again steam is wanted; when the fires are passed in under the boilers, air is re-admitted, the inflammable gases in the flues in part take fire, and are consumed, or pass off, and the vigorous combustion of the fuel is recommenced. The radiated heat of the fire, which had previously been absorbed by the brick-work of the arch of the cavity, is now carried off by the stream of cold air into the boiler flues, and becomes available, and thus no part of the fuel is lost at any period of the operation. This improvement is obviously applicable to boilers of any sort when intermittingly employed, for any other purpose, as well as on the present system of the atmospheric railway. The proportions of these boilers are taken from those of the best Cornish examples, and are calculated to boil off, from a temperature of 70° Fahrenheit, rather more than four cubic feet of water per minute into steam, at 45 lbs. per square inch above the atmosphere, five of the boilers being at work; and to perform this, with a consumption of not more than 5.9 lbs. avoirdupois of good coal for each cubic foot of water so evaporated. The boilers are jacketed as in Cornwall; the feed-water passes into a large pipe placed in the last flue (next the stack), and acquires there a temperature of nearly 212° Fahrenheit before it enters the boilers. A main steam-pipe, connected with all these boilers by stop-valves, unites with two branches by which steam is brought to the vacuum vessels and condenser. The vacuum vessels are two in number, and are to act alternately; each consists of two cylinders of boiler plate, stiffened by ribs on the outside, jacketed with sawdust and sifted ashes outside, and lined with staves of pine 3 inches 199 thick throughout the interior, as shown at large on the plans; the construction of the shell of the condenser is precisely similar, and its capacity is equal to that of one of the vacuum vessel cylinders. That is, the capacity of the condenser is one-half that of the vacuum vessel. The two cylinders forming each vacuum vessel are in free communication, and the only reason of using two cylinders in place of one, is, that a much larger diameter would be in danger of compression, unless stiffened at great cost; and a much greater length would be inconvenient. The capacity of the vacuum vessels is determined by that of the tube to be exhausted. Between each of the vacuum vessels and the condenser are placed three double beat valves, (or six valves in all;) the functions of one of them with reference to each vacuum vessel is to admit steam thereto alternately, and shut it off; of another, to establish or close alternately communication between the vacuum vessels and condenser; and of the third, to establish and close alternately communication between the vacuum vessels and railway tube. The object of lining both the vacuum vessels and condenser with wood (a bad conductor of heat) is, that the former being alternately filled with steam and with air at common temperature, and the latter having nearly a constant rush of steam into it to be condensed, it is desirable that the inner surfaces of these vessels should be in a condition neither to receive nor to give out heat; or in other words, to change temperature as little as possible, all such change being in the case of the vacuum vessels attended with waste of steam, and of the condenser with waste of condensing water. Condensing water is supplied to the condenser by a perforated pipe and stop valve, from a reservoir or source with a head of four or five feet of water. The condensing water and condensed steam are removed from the condenser, and the condensed steam that may form in the vacuum vessels, by means of inverted syphon pipes, with a balance valve at the lower end, and having a total difference of level between this point and the lowest part of the vacuum vessels or condenser of 34 feet. (To be continued in our next.) |