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TABLE II.

Maximum weight (tons) of Train on gradient of

Gauge

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1 in 2001 in 150 1 in 1001 in 80 1 in 60 1 in 501 in 40 1 in 301 in 25 1in20

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that one-quarter of this should be re- pulsometer, worked by the engine. It is served for emergencies, it would follow only at the engine sheds that a tank is that the watering stations should be one necessary, and this may be filled by hour's distance apart. But this assumes means of the steam left in the engines that the engine will always be exerting when they come in. As to the distance its maximum power, and, taking this and between the coaling stations, assuming other circumstances into consideration, that each pound of coal will evaporate 8 the watering stations may be placed at lbs. of water, and that the capacity of about double the above distance. They the bunkers is only one-quarter that of should be of the simplest character, gen- the tank, it will follow that this should erally consisting of a well from which be double the distance between the wawater may be drawn by an ejector or 'tering stations. – Glaser's Annalen.

ESCAPE FROM A SECOND TAY BRIDGE CATASTROPHE.

From “The Builder."

The banks of the Solway are the is at hand, the hills of the Isle of Man birthplace and the home of legend. The may often be distinctly seen, although region is resonant with ballad. The such vision is but the effect of mirage. magic of nature seems to have prepared High country intervenes between the a scene for the magic of romance. The shore of the Solway and the western craggy heights of Criffel look down on coast of the Irish Channel, so that the a noble estuary. The tourist who views appearance of this natural portent is in the spot from the lofty top of Skidaw itself a phenomenon fitted to dispose the sees fertile plains divided into numerous mind to the ready acceptation of the enclosures that look like gardens, while marvelous. Nowhere in the British the river, when the tide is in ebb, traces islands, except from the hills to the east a fivefold line to the sea. On either side of Cork, have we ever witnessed the rare are brown and glittering sands. Then deception of the fata morgana so plainly come two converging lines of turbid as on the banks of the Solway. water; and in the center is a narrow On the last day of January, in the streak glittering like silver. Nor are present year, the Solway very narrowly the charms of the natyral scene all that escaped becoming the scene of a calamiadd interest to the spot. Over the ty that would have been without a prebroad expanse of sand the sea some- cedent in all the ghostly tales of border times comes up in flood as fast as a horse lore. It was due to the simple, old-fashcan trot. And in the little fishing vil ioned, often derided precaution of the lage of Allonby, when stormy weather night watchman that the evil fame of

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the Solway viaduct has not rivaled the the width of nine of the 30 feet spans.
discredit of its sister structure across the The bridge was veiled in a dense fog
Tay-sister, that is to say, in object and through the night, and the damage done
in fate, albeit presenting little family was not fully ascertained on the morning
likeness in appearance; indeed, the very of the 1st.
opposite principles have been adopted The length of the viaduct is stated at
for crossing the two estuaries. In the 1,960 yards, and as the waterway is also
Tay bridge the central girders spanned given as 5,666 feet, only the width of 12
openings of 245 feet wide. In the Sol- inches is allowed for each pier. In fact,
way bridge the spans are only 30 feet. the supports of the girders appear to
Thús eight piers have to be reared in have been simple rows of iron columns,
the latter structure, for one on the for- of 12 inches diameter, five in a row.

The height and cost of the gird- These are described as sunk into the bed ers, which, on the Tay bridge were 27 of the Firth to an average depth of 18 feet deep, are proportionately dimin feet, the height being from 35 feet to 40 ished. The Solway bridge would have feet. If this be correct, it would seem felt almost nothing of the storm which difficult to design a mode of supporting blew down the Tay bridge. But the a river bridge which would form a more Tay bridge would have been but little effectual ice trap. A great number of affected (or might have been but little feeble columns, planted at the narrow affected) by the islands of floating ice intervals of 30 feet, afford a positive inthat crushed so many of the light and vitation to danger from ice or floating frequent piers of the Solway viaduct. wreck. The only things to cause sur

The Solway bridge has been open for prise are: How could the Board of traffic for above twelve years; it ought, Trade have sanctioned such a structure ? therefore, to be all the more remem- and, How is it that it has stood so long? bered, to the credit of the officials of It is curious that in the mode of crossthe railway company, that on the setting ing these two important estuaries such in of the thaw the bridge was carefully opposite ideas of economical structure watched. The accounts at present re- should have been carried out. No doubt ceived do not mention when the traffic the height of the rails above the sea had over bridge was suspended. It is, how much to do with this, as the Tay bridge, ever, evident that no trains were allowed if the accounts are accurate, was tbree to attempt to cross the Solway on the or four times as high as ihe Solway night of the 31st, for had such been the bridge-as high, that is to say, measured case, the catastrophe of the Tay bridge to the level soffit; for the depth of the would have been exactly repeated. So 245-feet girder was, of course, much loud were the crashes of the ice against more than that of the 30-foot girdthe piers of the bridge in the course of er. But if the height were fourthe night, that it was feared that serious fold, it is hardly a justification for an damage had occurred. By daybreak it eightfold difference in the span. In was seen that five of the piers, each con- point of fact, spans of 30 feet form alsisting of five hollow columns, of 12 most the cheapest possible arrangement inches diameter, had been destroyed, for a long viaduct. Where the expenses although the continuous line of girder of obtaining foundations are great, this and platform was so well bolted together circumstance has to form the basis of a as to be unbroken. Some of the other comparative calculation. In other repiers had been damaged; one, indeed, spects, while the cost per foot super. of had been damaged on the 29th. On the the platform, rails, &c., is the same for night of the 31st further damage was all spans, the cost of the main girders is done to the structure by the masses of almost directly as the squares of the ice borne by the high tides, and on the spans. In the Solway bridge the simple morning of the 1st instant a complete and inexpensive character of the piers was gap was made, to the width of 90 feet. such as to allow of the reduction of the This is about 600 yards from the Scot- span to the narrow width before stated. tish or northern end of the viaduct. But the economy was a pitiable one Nearer the Cumberland coast is a yet which dotted the bed of the Solway wider breach, extending, it is said, tol with rows of feeble columns, which

any hard winter menaced with over- study. But it must be a wise economy. throw.

The first oversight committed by the It is a remarkable circumstance that, great bridge builders of the railway in two cases presenting so close a par- times was that these structures were inallel, the pursuit of economy has led to sufficient to bear the weight of their the exposing of the several structures to own thrust, or the weight of their own the destructive action of two natural material, combined with that of a passforces against each of which the engi- ing train. It ought to lead us to view neer had ample warning to provide. For other errors with much consideration, to what

may be called a new danger in the reflect that two of the first engineers history of bridge building, the engineer that our country produced had to learn of each viaduct indeed provided. The the imperfections of formule on which, Roman engineers, and the French and together with their brethren, they relied, Italian architects, who reared the great by failure. Mr. Brunel's Maidenhead bridges, viaducts, and aqueducts which bridge fell down, by its own weight form some of the marvels of European when the centers were struck. Mr. Robarchitecture, never contemplated having ert Stephenson's Dee bridge broke down to design structures that could support with the first train that came on it after trains of carriages of hundreds of tons it had been covered with a coating of weight, whirling along at a speed of gravel. So that when we add to these from ten to fifty miles an hour. The the Tay bridge, fairly torn from its weight that could come on a Roman piers by a hurricane, and the Solway bridge was comparatively small. The bridge, with its legs knocked from under effect of wind pressure, even in such it by floating ice, we have practical warncases as the Pont de Gard, or the lofty ing of the force of the three chief differAlcantara aqueduct, was not formidable ent dangers with which, as before said, against the weight of the solid masonry the bridge builder has to contend. May of piers and arches. Of the three ele- we not hope that the fourth catastrophe ments of overthrow against which the may cause all concerned to put to themold bridge builders had to provide, viz., selves the question whether, in looking moving weight, pressure of storm, and to cheapness, they have provided against shocks from foods or from floating bod- every source of danger ? . And we must ies borne down by floods, no doubt by add that a special warning has been far the greatest amount of attention was given to look to the soundness of all given to this last-named risk. In Old great viaducts, more especially those London Bridge, as we have mentioned made of iron. The loss incurred by the in another place, there were 10 feet of destruction of the Solway bridge is very pier to 7 feet of arch. When the engi- heavy. Watchfulness prevented it from neer attempted to cross a deep estuary being fatal. We should like to be conby gigantic strides, he forgot how great vinced that there are no other cases in a destructible surface he exposed to the which very probable causes of danger fury of the wind. On the other hand, have been overlooked in construction, or when he attempted the same task by in which rust, vibration, or molecular short and numerous steps, and thus pro- change has not been allowed to make vided in the most economical way for silent inroads on the margin of stability.

,

duced a structure that could defy the The manufacture of tin plates origin

wind, he forgot how liable were his nu-ated in Northern Germany, and as a trade merous and slight supports to be swept had existed many years in Bohemia. From away by ice, or by any floating matter Bohemia, in 1620, it was carried into dashed against them by tide or by cur- Saxony by the Duke of Saxony, and from rent.

Saxony the secret came to England in It is not to the credit of our practical 1670 and was tried at Pontypool, but was architectural knowledge that we find, on given up and neglected until 1720, up to the two opposite coasts of Britain, one which date our ancestors had imported bridge builder falling into Charybdis, tin plates from Hamburg, though tin had while the other falls into Scylla. Econ.

gone froin our shores to other countries. omy is a great point for the architect t

-English Papers.

EXPERIMENTS ON THE ACTION OF FATS AND MINERAL LUBRICANTS ON IRON, IN THE PRESENCE OF

HIGH-PRESSURE STEAM.

From “Abstracts" of the Institution of Civil Engineers.

It is well known that steam of high temperature decomposes natural fats,

I.

II. IIL. and causes free acids to separate from

Deposit Deposit Deposit

from from from them. When used as lubricants, in

Condenser. Cylinder. Boiler. cylinders employing high-pressure steam, the resulting acids corrode the metal surfaces with which they come in con

Per cent. Per cent. Per ct. Water....

10.59 0.23 0.88 tact. With steam of very high pressure, Miueral oil... 36.29 18.43 1.50 this takes place with great rapidity; Fatty acids....

2.70

0.58

24.19 { with steam of medium pressure it con- Neutral fats.

2.14 0.12 tinues, though to a less degree; but it Copper) In the

1.78 2.11 Lead

1.08 0.50 goes on also even in the damp atmos

metalZinc

0.30 0.40 phere, as is proved by fats turning Iron

lic state

7.37 21.44 rancid when exposed to the air. In Oxide of iron... 16.0 46.58 74.26 engines provided with surface con- Peroxide of iron.

14.68

0.32 trace 5.34 densers, the result may be serious in- Gypsum. ...

Salt, common...

0.74

trace 1.93 jury to the boilers ; for the fats carried

Organic dirt.

2.98 2.58 0.58 away from the cylinders with the exhaust Inorganic dirt... 1.79 2.89 trace steam, are returned to the boilers in the feed-water and are there decomposed. The continuous action of hot steam cylinder, and boilers of a marine engine. causes also the generation of volatile The lubricants used were, first, tallow, acids, which leave the boiler with the and then, till the day of the experiments, steam, and injuriously affect steam pipes mineral oil. The metal found in the and cylinders. In this way the speedy deposit existed in the state of very fine destruction of boilers fed from surface dust, which preserved its metallic brightcondensers is generally accounted for. ness perfectly. The iron was in such a Some persons attribute this destruction, minute state of subdivision that, after to a certain extent, to the use of distilled separation from the compound, it burnt feed-water. In consequence of all this, spontaneously with a bright red heat on mineral oils, which consist chiefly of exposure to the air. These particles of hydro-carbons, and which do not suffer metal were of course produced by the decomposition at the ordinary tempera- friction of the piston, etc., and it is a ture of steam boilers, have come into matter of special importance to observe use, although as lubricants they are far that, in spite of their minute subdivision, from efficient at high temperatures. and prolonged exposure to the oxidizing One circumstance should, however, be influence of water and steam of high mentioned, which somewhat diminishes temperature, they were, nevertheless, the usefulness of mineral oils, viz., at perfectly free from oxidation. Apparhigh temperatures mineral oils adhere ently the remains of the lubricants had to the sides of the cylinders less than preserved them; and hence the question water does, and consequently, when arises—in opposition to the commonly steam is shut off, the condensed water received views—to what extent do these rusts the surfaces more than it would residues of the lubricants preserve do, were animal fats used. The follow- metals from the oxidizing influence of ing experiments were all made in conse- water and steam? quence of the remarkable results given To solve this question a strong copper by the following analysis of the sedi. boiler was made use of, connected by ment deposited in the surface condenser, means of a pipe with a receiver, having

& screwed top. Into the receiver were after the experiments, were thoroughly placed small vessels, which contained cleaned and again weighed. The differthe metal plates and the different lubri- ence in the weights gave the amount of cants to be experimented upon; so that iron lost by oxidation. The experiments any differences in the corrosion of the were made with both sea and distilled plates could only be ascribed to the water. The plates were half immersed action of the lubricant. The pressure in the water, their surfaces having been in the boiler was maintained at from two painted with the lubricating material, a to three atmospheres above the air press- little of which was also poured on the ure. The test-plates were accurately- surface of the water. The following weighed pieces of boiler plates, which, table gives the results:

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Experiments 1 to 6 prove that sea- the author to account for the destruction water alone and its steam destroys iron of the boilers, no account being taken of more rapidly than when tallow and min- the direct action of the acids. When eral oil are present. The tallow, when the lubricants come into the boiler, and fresh, contained 0.4 per cent. free acid, acids are formed, these latter, acting on and after six days' exposure to steam, the lime and other alcalic minerals in the 3.4 per cent. Experiments 7 to 9 prove feed water, form insoluble soaps, which the same thing with regard to distilled are deposited on the sides and bottom of water, and prove also that distilled water the boiler, furnaces, etc. Furthermore, is less harmful than salt water.

the fatty acids, acting on the oxide of In experiments 10 to 12 the plates, iron contained in the feed-water, or exwhich were before exposed to the pure isting on the boiler-plates, form insoludistilled water, were now coated with the ble iron soap, which also is deposited in lubricant, and vice versa, but without a similar manner. These soaps are nonaltering the result.

conductors, and in consequence the The oft-observed fact, that boilers of plates which are covered by, and which engines provided with surface conden- are also exposed to the action of the fire, sers have a very short life-time, must are overheated and rapidly destroyed. therefore be ascribed to some other An illustration of this action may be obeffect of the lubricating material than tained by boiling sea-water in a platinum the generation of acids, for it has been basin, over a moderate steady flame. proved above that, in spite of the pres- Under these circumstances the boiling ence of acids, the lubricants tend to pre- proceeds quite quietly. Let now a few serve the plates from rust.

drops of an oil rich in acids be dropped The following reason is advanced by on the water ; after a few moments the

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