Chapter 3

In the accompanying engravings, Fig. 1 shows a front elevation (partly in section) of a pair of engines constructed according to this invention. The lower part, A, of each cylinder is cooled by water circulating through its casing. The upper part, B, is lined with refractory material, such as fire-clay. The trunk piston, C, is made hollow, and formed with a shield covered by refractory material to protect the packing of the piston and the surface of the lower part of the cylinder from heat. The pistons of the two cylinders are connected by rods, D, to opposite cranks on the shaft, E. This shaft, by means of bevel gear, F, works a revolving cylindrical valve, G, situated in a casing between the two cylinders. The lowest part of this casing is supplied with combustible gas and with air, in proportions capable of being regulated by stopcocks or valves. The highest part of the casing communicates with a discharge-pipe; and the middle part of it with a reservoir which can be cut off from communication by a stopcock, so that the charge in the reservoir may be retained when the engine is stopped. The middle space of the hollow valve, G, communicates, by a number of holes, with the middle space of the slide casing. It also, by means of a port at its lower part, communicates alternately with the annular spaces of the two cylinders; this communication in each case being made when the piston is performing the latter part of its downstroke. The interior of the slide also, by means of a second port at its upper part, communicates alternately with the tops of the two cylinders; this communication being in each case made while the piston is performing the first portion of its downstroke. During the upstroke of each piston the slide, by means of another port, makes communication alternately to each cylinder from the bottom of the slide casing, and by means of a fourth port make communication alternately from each cylinder to the top of the slide casing. In the passage connecting the top of the slide casing to each cylinder is placed a regenerator, consisting of a number of perforated metal plates or sheets of wire gauze.

In order that gas of poor quality or gas diluted with a large proportion of air may be utilized, an igniting arrangement is employed which operates as follows: I is a vessel containing a supply of hydrocarbon oil, preferably of volatile character. From this vessel pipes lead to two cocks, one for each cylinder; these corks being caused to revolve in time with the engine-shaft by a chain, M, communicating motion from a wheel on the engine shaft to a chain-wheel of equal size on the spindle of the two cocks. The plug of each cock has on its side a small hollow, which during one part of its revolution presents itself under the oil-pipe, and receives a charge of oil. During another part of its revolution, which is timed to correspond with the flow of gaseous mixture to the cylinder, the hollow of the plug presents itself to the bend of a pipe leading from the top of the cylinder to a port opening into the cylinder below the regenerator, in which port are situated two wires of platinum. These wires are connected with the brushes of a commutator, K, on the engine-shaft, which commutator is in electrical connection with the poles of a battery, dynamo-electric machine, or other source of electricity. Instead of two wires to produce a spark, a single wire may be arranged to become incandescent at the proper time for ignition.

The operation of the engine is as follows: Each piston as it ascends draws into the annular space under it a supply of gas and air in proportion regulated by the cocks or valves, and as it descends it forces this charge into the interior of the revolving valve and its casing, and into the reservoir which communicates therewith. When either piston is at the top of its stroke, the revolving valve admits to the upper part of the cylinder a supply of the gaseous mixture from the reservoir and valve casing, and this passes through the generator. At the same time a portion of the charge passes by the pipe, and becomes enriched by admixture of the hydrocarbon oil delivered to it by the cock. The enriched mixture, in passing the platinum wires, which at that time give an electrical spark, is ignited, and ignites the charge that is passing through the regenerator into the cylinder. The mixture thus ignited expands, and acting on the full area of the piston propels it downward, the under side of the piston being at that time subject to pressure only on its annular area. When the piston has completed its down-stroke the passage is opened to the discharge-pipe, and the expanded products of combustion then pass from the cylinder through the regenerator, and are discharged. In their passage they give out to the regenerator a large portion of their heat, which the charge entering the cylinder for the next stroke receives in passing through the regenerator.

Fig. 2 is a vertical section of a gas producer and scrubber, which, as stated above, may be employed in combination with engines such as have been described for supplying them with combustible gas. The producer is a vessel lined with refractory material. At the top it has a supply opening covered by a cap, U, having a flange dipping into a sand joint. At the bottom it has an opening surrounded by inclined bars, V, which rest upon a water-pipe perforated with small holes, by which water issues to cool the bars and generate vapor. This vapor rises along with a limited supply of air through the incandescent fuel above, and combustible gas is produced, which collects in the annular space, and is led thence by a pipe to the scrubber. The scrubber is a vessel containing in its lower part water, W, supplied by a pipe, and having an overflow. By means of a perforated deflecting plate the gas is caused to bubble through the water, whereby it is cleansed and cooled, and it passes by a pipe, X, to supply the engine. The upper end of the vertical pipe of the scrubber is made open and covered by a cap sealed in water while the producer is at work. In starting the producer this cap is removed and a chimney pipe put in its place, so as to give a draught for kindling the fuel in the producer. When the fuel is kindled the chimney is removed and the cap substituted, whereupon the suction of the engine continues the draught as required.

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THE BAZIN SYSTEM OF DREDGING.

By MR. A.A. LANGLEY.

This paper, lately read before the Institution of Mechanical Engineers, London, is a description of the construction and working of a dredger on M. Bazin's system, as used by the author for the past three years in dredging sand and other material in Lowestoft Harbor. The dredger is represented in its general features on next page, Fig. 1. The total length of the hull is 60 ft., with 20 ft. beam. In the after part of the hold is placed a horizontal boiler, A, which supplies steam to a pair of inverted vertical engines, B. These engines drive, through belts and overhead pulleys, a centrifugal pump, C, which discharges into the open trough, H. The suction pipe, D, of this pump passes through the side of the dredger, and then forms an elbow bent downward at an angle of 45 deg. To this elbow is attached a flexible pipe, E, 12 in. in diameter and 25 ft. long, made of India-rubber, with a coil of iron inside to help it to keep its shape. At the lower end of this pipe is an elbow-shaped copper nozzle which rests on the bottom, and is fitted with a grating to prevent stones getting into the pump and stopping the work. The flexible tube is supported by chains that pass over the head of a derrick, F, mounted at the stern of the dredger, and then round the barrel of a steam winch. By this means the depth of the nozzle is altered, as required to suit the depth of water.

A man stands at the winch, and lifts or lowers the pipe as is required, judging by the character of the discharge from the pump. If the liquid discharged is very dark and thick the nozzle is too deep in the sand or gravel; if of a light color the pipe must be lowered. The best proportion of water to sand is 5 to 1. When loose sand is the only material to be dealt with, it can be easily sucked up, even if the nozzle is deeply buried; but at other times stones interfere with the work, and the man in charge of the flexible tube has to be very careful as to the depth to which the nozzle may be buried in the sand. The pump is shown in Figs. 2 and 3. The fan is 2 ft. diameter, and has only two blades, a larger number being less efficient. The faces of the blades, where they come in contact with the sand, are covered with flaps of India-rubber. Small doors are provided at the side of the pump for cleaning it out, extracting stones, etc. The fan makes 350 revolutions per minute, and at that speed is capable of raising 400 tons of sand, gravel, and stones per hour, but the average in actual work may be taken at 200 tons per hour. This is with a 10-horse power engine, and working in a depth of water varying from 7 ft. to 25 ft. The great advantage of this dredger is its capability of working in disturbed water, where the frames of a bucket dredger would be injured by the rise and fall of the vessel.

Thus at Lowestoft bucket dredgers are used inside the harbor, and the Bazin dredger at the entrance, where there are sand and gravel, and where the water is more disturbed. The dredger does not succeed very well in soft silt, because, owing to its slow precipitation, it runs over the sides of the hopper barges without settling. Nor does it do for dredging solid clay. It gives, however, excellent results with sand and gravel, and for this work is much superior to the bucket dredger. The experience in working was then described, showing that a great many very discouraging failures preceded successful working, about a year being expended in getting good results.

COST OF WORKING.

The vessel or barge for carrying the machinery and pumps cost £600, and the contract price of the machinery and pumps was £1,200. But before the dredger was taken over by the company the alterations before enumerated had cost about £300, bringing the total for barge and dredger up to £2,100. In building a second dredger this might of course be greatly reduced. The cost of repairs for one month's working has been only £5. The contractor receives for labor alone 1-1/8d. per ton, being at the rate of about 1¾d. for the dredging and 3/8d. for taking to sea--a lead of two miles--all materials being supplied to him. The consumption of coal is at the rate of about 1 ton for 1,000 tons of sand dredged. At Lowestoft Harbor the total amount of dredging has been about 200,000 tons yearly, but this is now much reduced in consequence of the pier extension recently constructed by the author, which now prevents the sand and shingle from the sea blocking the mouth of the harbor. The total cost of working has been 2.572d. per ton. which with 10 per cent interest on capital, 0.240d., makes the total cost per ton 2.812d. The repairs to steam tug, hopper, barges, and dredger have averaged about 2d. per ton.

Before the discussion on the paper commenced, Mr. Langley remarked that attempts had been made to connect the engine direct to the pump of a Bazin dredger, but this arrangement failed, and the belt acted as a safety arrangement and prevented breakage by slipping when the pump was choked in any way. A new lock was constructed near Lowestoft a short time ago, and the dredger pump was used to empty it; when half empty the men placed a net in front of the delivery pipe and caught a cartload of fish, many of which where uninjured. In the discussion Mr. Wallick, who had superintended the use of the dredger at Lowenstoft, gave some of his experience there, and repeated the information and opinions given by Mr. Langley in the paper.

Mr. Ball, London agent for M. Bazin, said that as devised by M. Bazin the pump was placed below water level, so that the head of water outside should be utilized; but he--Mr. Ball--now placed the pump considerably above water level, as no specially formed craft was thus necessary. He also described some of the steps by which he had arrived at the present arrangements of the whole plant, and gave some particulars of its working. Mr. Crampton asked some questions, in reply to which Mr. Ball said the longest distance they had carried the material was 1,200 yards in two relays--namely, a second pump on a floating barge with special engine. The distance to which they could carry the material depended upon its character. Fine sand would travel well; mud would not, bowlders would not, though gravel would. To give the water a rotary motion he had inserted a helical piece of angle iron, and so prevented deposition.

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DANGER FROM LIGHTNING IN BLASTING.

Although the accident in the tunnel in process of construction at Union Hill by the New York, Ontario, and Western Railroad Company, which took place on Tuesday afternoon, was happily attended with no loss of life or serious injuries to the men employed in the shaft, it reads a new lesson as to the firing of charges of powder by electricity, and one that should be carefully noted by railway and civil engineers, and even by the torpedo service of the United States. The exact cause of the explosion has scarcely been fully and accurately set forth by the various reports of the affair.

It appears that the wires usually employed lo supply the electric lamps in the excavation were used for the purpose of firing the charges, being disconnected from the electric light system for the moment and connected with the explosives. As a rule, six charges were fired together, those of the afternoon relay of men being exploded at very regular hours--the last usually at 5:45 P.M. There were only sixteen men in the shaft, and the work of connecting the wires had commenced, when the flash of lightning that occurred at 5:42 P.M., suddenly charged the conductors and produced the explosion.

There were two flashes of lightning between the hours of 5 and 6 o'clock Tuesday afternoon, the first taking place at 5:23, and the second nineteen minutes later. The former, according to testimony elicited by our reporter, simply caused a slight perturbation of the lights in the tunnel, but did not extinguish them. Five minutes later the work of disconnection and reconnection began, but only two of the six charges were ready for the pressure of the button when the last flash interrupted the proceedings. The fact that the time of the explosion corresponded to the second with that of the aerial electrical discharge furnishes indubitable evidence that the accident was not caused by any carelessness on the part the electrician in charge, and exonerates all parties from blame. At the same time it should be remembered by engineers in of such work that atmospheric electricity cannot be altogether disregarded in such cases, and that as a source of accident it may at any time prove dangerous. The concurrence of circumstances on Tuesday was particularly fortunate. In the first instance only two of the six charges had been connected with the firing battery, and in the second the rock in which the charges were inserted was so peculiarly soft and porous as to deaden the force of the eight pounds of giant powder thus prematurely set off. Had the cartridges been set in the harder and more solid rock of the east heading, instead of the west, and the explosion taken place there, probably not a man in the shaft would have escaped destruction. The lesson to engineers is one of no less importance than if the whole number of men had been killed, and should lead to the exercise of great care and precaution at times when the air is charged with electrical energy.--_New York Times_.

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CAST IRON IN ARCHITECTURE.

Whatever may be the misgivings entertained by many engineers respecting the future use of cast iron for structures of certain kinds, it is clear that for architectural purposes this material is likely to be employed to an extent hardly contemplated by many who have looked upon it with disfavor. At the present moment many buildings may be seen in London, in which cast iron has been introduced instead of stone for architectural features, and the substitution of cast iron for façades in many warehouses and commercial buildings seems to show that, notwithstanding the prejudices of the English architect against the importation of the iron architecture of our transatlantic brethren, there is a prospect of its being largely employed for frontages in which ample lighting and strength are needed. The extensive window space necessary in narrow city thoroughfares, and the difficulty of employing brick in large masses, such as pilasters and lintels, have chiefly led to the adoption of material having less of the uncertain durability and strength of either stone or terra-cotta in its favor. Architects would gladly resort to the last-named material if it could be procured in sufficient size and mass without the difficulties attendant upon shrinkage in the burning, and the winding and unevenness of the lines thereby caused. They have also an even more tractable material in concrete ready to their hand, if they would seriously bring themselves to the task of stamping an expressive art upon it, instead of going on designing concrete houses as if they were stone ones. Cast iron has the advantage of being a tried material; it is well adapted for structures not liable to sudden weights or to vibration, and so it has come to be used for features of an architectural kind, by a sort of tacit acknowledgment in its favor. Those who are desirous of seeing examples of its employment in fronts of warehouses will find instances in Queen Victoria Street, Southwark Street, and Bridge Road, and Theobalds Road, where the whole or portions of fronts have been constructed of cast iron. At some corner premises in Southwark, the piers as well as the windows are formed of cast iron, the former being made to assume the appearance of projecting pilasters. There is nothing to which the most captious critic could object in the treatment adopted here; the pilasters and other features have plain moulded members, and there is no principle of design in cast work which has been violated--the only question being the purely aesthetic one--is it justifiable to copy features in cast iron which have generally been constructed in stone or marble? The answer is obvious: Certainly not, when those features suggest the mass and proportions or treatment proper only for stone or marble; but when they do not so represent the material, it is quite optional for the architect to build up his front with castings, if by so doing he can obtain greater rigidity of bearing, strength, and durability. He ought, of course, to vary the proportions of his pilasters and horizontal lintels, and make them more in accord with the material. It is the wholesale reproduction of the more costly and ornamental features, such as we see in many buildings of New York and Philadelphia, where whole fronts are manufactured of cast iron and sheet-metal, which has shocked the minds of architects of culture and sensitive feeling. Such imitations and cheap displays outrage the artist by the attempt to produce in cast or rolled metal what properly belongs to a stone front.

Bearing this distinction in mind, we are not presuming too much to assert that architects have in cast iron, when properly employed under certain restrictions, a material which might be turned to account in narrow fronts where the use of brick or stone piers would encroach too much upon the space for light. For warehouse fronts, we have evidence for thinking that the employment of iron might be attended with advantage, especially in combination with brickwork for the main vertical piers. Plain classic mouldings, capitals and bases of the Doric or Tuscan order, are well suited for cast-iron supports to lintels or girders. In one attempt to make use of the structural features of the latter, the fronts of the girders between the piers are divided into panels, the flanges and stiffening pieces to the webs forming an effective framework for cast or applied ornament to be introduced. The iron framework thus constructed lends itself to the minor divisions of the window openings, which can be of wood. In the new Leaden Hall and Metropolitan Fruit and Vegetable Markets, cast-iron fronts have been largely employed, consisting of stanchions cast in the form of pilasters, with horizontal connections and other architectural members.

Regarding the more constructive aspects of cast iron, the employment of it in fronts having numerous points of support and small bearings is clearly within the capabilities of the material. So long as it is used in positions in which its resistance to compression is the chief office it has to fulfill, cast iron is in its right place. In the fronts of buildings, therefore, where it is made to carry the floors and rolled joists, and the lintels of openings, either as piers, pilasters, or simply as mullions of windows, it is strictly within its legitimate functions. So with regard to lintels and heads of openings where short spans exist, cast iron is free from the objection that can be urged against it for long girders. In fact, no position is better fitted for a brittle, granular material than that of a vertical framework to receive windows and ornamentation, and for such purposes cast iron is, to our minds, admirably suited.