depression of the water-surface below the level of the flues. In this case the tube passes obliquely from the top of the boiler through it, and terminates in the side to be protected, and the plug-form of the stopper is changed to that of a ball. Should the water-depression take place, and the boiler-side become, in the absence of water, 'too much heated by the action of the fire, the ball will melt like the plug in the first instance, and the same desirable consequences will follow. M. G.-C. also suggests, that the injection-pipe of the water-supply should extend further into the boiler than usual, and be carried quite round its sides at the greatest convenient height, and that this prolongation should deliver the water through a large number of small holes, so distributed that they should bathe the whole interior surface of the sides. This would be another means of preserving them at all times from injurious increases of temperature, even when the water in the boiler might be the lowest possible. Self-regulating Apparatus for the Supply of Steam-Boilers. As the most frequent cause of the explosion of steam-boilers arises from the depression of the water-surface below a certain level, it is evident that the constant maintenance of this surface at a proper height, is an object of the highest importance. It appears, from causes into which we shall not now inquire, that much more attention has been paid to this essential appendage of a safe boiler in the United States and in France, than in this country. We select two instances to which publicity has recently been given, in the latter kingdom, by the Société d'Encouragement. One of these is of universal application, and possesses that extreme simplicity which characterizes the results of refined invention. M. Galy-Cazalat, whose safety-stopper has been described in a preceding page, is also the author of this apparatus. To the chamber of a feeding-pump (which has a power more than sufficient to supply the greatest evaporation, leakage, &c., of the boiler to which it is applied), M. G.-C. attaches a very small tube, this he leads into the boiler, and establishes a second connexion between them, the first being the usual one,-that of the injection-pipe. This small tube rises in the boiler to the required water-surface level, and there expands into a cup-shaped termination. In this lies a hollow metallic sphere, light enough to float in water; and though allowed a certain play, yet is prevented by a bridle from escaping, and thus acts as a valve. This is the whole apparatus; its action is as follows:-When the supply happens to be larger than the evaporation, &c., takes off, the water-surface naturally rises in the boiler; this rising lifts the spherical valve out of its seat, and permits a small quantity of the hot water to pass through the tube into the pump, the next exhausting stroke of which, by producing a vacuum, changes the hot water into a volume of steam, which, filling the pump, prevents the rise of water, and checks the supply. The succeeding strokes of the pump continue ineffective by the same means: they merely create and compress steam, until the water in the boiler is so much evaporated, that its surface descends low enough to reseat the spherical valve, and cut off the connexion between the boiler and the pump; this done, no more hot water can descend, the steam in the pump is condensed, and the latter recommences the water-supply; a little time may be necessary in the warming and cooling of the pump before its full operation can, in each change, be attained, but the range of water-surface in the boiler, through which it may safely travel, is always sufficiently ample to permit this. To facilitate the cooling, the piston of the pump is made hollow, so that the atmosphere may have access to it. As, in order to ensure the buoyancy of the metallic sphere, it must be made very thin, and therefore unequal to sustain great pressure when occurring on one side only, M. G.-C., to prevent its being crushed by the steam, encloses a little water within it. This is, of course, raised into steam of the same elasticity of that which surrounds it, and exactly balancing the external pressure, preserves the sphere from a change of form. The other apparatus referred to has been adopted by the proprietor of a large establishment in France, and can be used in stationary steam-boilers only. The apparatus consists in a receiver and two stop-cocks, put in action by a counter-weight, which is raised occasionally by an hydraulic lever. A correct idea of the arrangement may be formed by imagining a cylinder to be attached to one end of the beam of a balance, and a weight at the other. The receiver, by its position with regard to the steam-boiler and a reservoir of water, can be suddenly filled with either water or steam. Its weight is thus varied, and will become either greater or less than the counter-weight. When filled with water it is greater, and, of course, the beam declines on the side of the receiver. When this is replaced by steam, the counter-weight is heavier. This then descends, and raises the receiver. The axis of the beam is in connexion with the stop-cocks, which, in the several positions resulting from the movement of the beam, open communications alternately with the reservoir and with the boiler. When the receiver has obtained its dose from the reservoir, it descends by its superior weight; a stop-cock is opened, and, if the water-level be low, the contents of the receiver pass into the boiler; and the former losing weight by the exchange of water for steam, is lifted by the counter-weight to the reservoir, and, receiving a further supply, again descends. If the water-level be sufficiently high, though the communication by the stop-cock be made, yet no water passes, and the receiver remains stationary until the water-level descends below the assigned point. This last effect is owing to the orifice of communication being below the desired water-level; and of course not being open unless the water-surface has descended below it. This mode of feeding a boiler has been in actual operation, in the establishment in which it is erected, for several years, and its success has completely demonstrated the practicability and the value of the design. Another Bequest to the Ingenious. "To the President for the time being of the Civil Engineer Institution in Trust, the interest to be expended in Annual Premiums, under the direction of the Council, Two Thousand Pounds. "All my scientific Books, Book-cases, Prints, and such Drawings as my Executors shall consider suitable, are to be delivered to the President of the Civil Engineer Institution, for its use and benefit, on condition that all those Articles, as well as the Books, Prints, and Drawings already presented by me, shall, in case of the said Institution being discontinued, be delivered to the Royal Society, Edinburgh, for its use." EXTRACT from the WILL of the late THOMAS TELFORD, Esq., In our last Number we inserted the noble Bequest of John Scott, of Edinburgh, who, far away from his native country, left a considerable sum of money for the encouragement of the useful arts; and we also thought it a duty to animadvert on the conduct of those parties in whose hands the distri . bution of the proceeds of the legacy were ultimately left. We have now recorded a later case of the same public-spirited description. Mr. Telford, also a Scotchman, also dying, though in London, yet far removed from Scotland and his native place, bequeaths also a considerable sum of money for a very similar purpose. The case is, indeed, so far so precisely parallel, that we proceeded with more than ordinary interest to ascertain the conduct of the trustees or their agents to whom the care of the latter bequest was confided. We certainly did venture to hope that the parallelism might not continue further in the two cases, but we were determined, if it did, to express ourselves as freely, at least, of the Institution of Civil Engineers of London, as we had done of the Franklin Institute of Philadelphia. We are glad to announce, as Englishmen and as men, that our hopes were realized, and we have the gratification to subjoin, for the information of the ingenious throughout THE WORLD, the following resolutions of the Council, under whose direction Mr. Telford has left the interest of the £2000 to be expended. Extract from the Minutes of a Special Meeting of the Council of the Institution of Civil Engineers, held 23rd February, 1835. RESOLVED, upon consideration of the above bequest of their late highlyesteemed and much-lamented President, that I. The Premiums to be given be both of an honorary and pecuniary nature. II. That the honorary premiums consist of medals in gold, silver, and bronze, to be called the "Telford Medals," with a head of the late president on one side, surrounded by the words, “Institution of Civil Engineers, founded 1818;" and on the other "Telford Medal," and a suitable device, leaving a space for the name of the successful candidate, and the object of the reward; or of such other description of honorary medals, and of such size and value as shall be determined by the Council. III. That the principal subjects for which premiums will be given are1. Descriptions, accompanied by plans and explanatory drawings, of any work in civil engineering, as far as absolutely executed; which shall contain authentic details of the progress of the work*.—2. Models or drawings, with descriptions of useful engines and machines; plans of harbours, bridges, roads, rivers, canals, mines, &c.; surveys and sections of districts of country.-3. Practical Essays on subjects connected with civil engineering, such as geology, mineralogy, chemistry, physics, mechanic arts, statistics, agriculture, &c., together with models, drawings, or descriptions of any new and useful apparatus, or instruments applicable to the purposes of engineering or surveying. IV. No premiums can be given until the next session of the institution, but specimens of the "Telford Medals" will, if possible, be provided for the inspection of the members previous to the close of the present session; and any communications for reward, presented during the present session, will be considered as subjects for premiums in 1836. V. The number or nature of premiums to be determined by the Council at a special meeting or meetings to be called for that purpose. No member of the Council can be present at any meeting for determining the premium of the class for which he may be a candidate. The quorum of the council for deciding on the premiums must consist of at least the president, two vice-presidents, and four members, or in case of the unavoidable absence of the president, of * Smeaton's account of the Edystone Light-house may be taken as an example. three vice-presidents, and four members of the council; being in either case seven, as the smallest number of a Council for awarding premiums. VI. The premiums to be distributed to the successful candidates at a special general meeting at the end of the session. VII. In the distribution of premiums no distinction will be made between natives and foreigners. VIII. The proceedings in Council respecting the premiums to be made known at the ordinary meeting of the 24th of February, from the chair; and that printed copies of the same be circulated to every member of the Institution, together with the substance of the address of the President on the 27th of January, 1835. To the bequest of Mr. Telford and these resolutions, and particularly to the seventh, we desire the same extensive attention that we requested to the legacy of Mr. Scott, and to the terms in which it was actually bequeathed; and further we appeal to the justice of the Franklin Institute, that they will enable us soon to announce that the following statement and contrast has ceased to be true. The proceeds of a legacy of £530 were left to " ingenious men and women," by a Scotchman dying in America. The Franklin Institute of the state of Pennsylvania for the promotion of the mechanic arts, endeavour to limit the knowledge and the advantage of the bequest to "the ingenious of the United States only." The proceeds of a legacy of £2000. were left" to be expended in annual premiums" by a Scotchman dying in London. The Institution of Civil Engineers of London, at liberty to make any restriction or condition they please, take no advantage of their position, but decide that in the distribution of the premiums no distinction shall be made between natives and foreigners." 66 Estimate of the Efficacy of the Hot-Air Blast. THE calculations, &c., of M. Clement Desormes, have induced him to conclude that the temperature of the furnace for smelting iron is increased 270°,—360° Fahr., by the introduction of the hot-air blast; and he states, that he considers this increase to be adequate to the explanation of all the observed effects. Estimate and Expression of the Value of Acclivities in Roads. Ir is evident that, if it were possible, by calculation and the correct reduction of the various kinds of difficulties into equivalent quantities of the same kind, the comparison of two lines of road, of whatever material or construction, might be simply and satisfactorily expressed, either by numbers, or (to the eye) by lines of proportionate length. Supposing, for example, there were two roads leading from the same commencement* to the same terminus, and that it were wished to express, as concisely as possible, the merits of each, could it be done better than by saying the balance of the advantages and disadvantages of the one, compared with the other, are as (suppose) 5 to 4; or more extendedly, that 50 miles might be run in the same time, with the same load, as 40 miles on the other; or supposing one line to be entirely level, and the other has depreciating acclivities, if it were said that 90 feet of rise in the latter were equivalent to a * In the parliamentary engineering language of the present session, there is no word expressive of the commencement or starting point of a rail-road, nothing but "terminus" and "termini," are yet provided. So that English gentlemen and English counsel are constantly talking about "beginning at the end (terminus) of such and such a railroad!" mile of distance on the former, &c.? The quackery and humbug of such terms as “characteristic gradient" would then, as they ought, be banished from all rational discussion. Nothing can be more amusing or pitiable than the frequent misapplication of the barbarous term "gradient," both by engineers and legislators, in the present parliamentary committees. The invention of this term, it is said, originated with a drunken Irishman (an engineer!), who endeavouring to give the proprietors of a road, in a hilly district, some excusc for an excess of cost over estimate, hiccupped out "that the rise over Hill must be an in-in-n―n-gradient in their calculation." "Is it in gradient you mane ?" said the chairman. "It-it is," said the engineer. When the reasoning and formula given by Navier, in his Essay on the comparison of competing Lines of Railroads *, are better understood, the jargon and mystification we complain of will be unknown, and common sense may preside unruffled in committees, &c., on engineering subjects. Railroad Acts, present Session, (June 24th incl.) THE following additional Railroad Bills have received the royal assent: 10. June 7. Brandling Junction. 15. June 21. Birmingham, Bristol, and Thames Junction. 11. 21. London & Dover (South eastern.) Newcastle 14. Merthyr Tydfil and Cardiff. Deptford Pier Junction. British Association.-Sixth Meeting. THE sixth meeting of the British Association for the Advancement of Science, is definitively announced to commence at Bristol, on Monday, the 22nd of August. It will continue during the whole week. The officers of the association assemble on Saturday, the 20th of August, to make the necessary arrangements. They must work on Sunday, if Monday and part of Tuesday are not to be lost to the members as usual. Patent Law Improvement Bill. THE following notices appear in the printed votes of the House of Commons. We have searched the journals of the public press in vain for any notice of them, or for further information relating to their important object. The bill itself is not yet (June 25) printed for public circulation. June 14th, 1836.-" Act (5 and 6 Will. IV., c. 83+) read. Bill to amend the said act, ordered to be brought in by Mr. Mackinnon and Mr. Hardy §." June 20th, 1836.-" Bill to amend the law relating to Letters Patent for inventions, and for the better encouragement of the arts and manufactures,' presented and read 1°; to be read 2° on Wednesday, 29th June, and to be printed." A change seems to have taken place in the intended parliamentary proceedings on this subject. Whether Mr. Mackinnon asked for the committee for which * Lately translated by Mr. Macneill, see p. 60 of the present volume. |