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made on a much more honest amount of work done, and that such a charge would at any time show a stock more like what it ought to be than

the other.

I consider the only fair and proper method of charging expenses to be on the number of miles in actual service drawing trains, whether of loaded or empty vehicles. Necessity will frequently require that engines be sent out on trips, or run "return trips" empty or without a load, but these distances have no right to be placed to their credit of mileage account in repairs. A good engine should never be within giving a few occasional miles empty.

I propose to show calculations made upon an extreme, and also upon a more moderate amount of work done. Premising, however, that they have been based upon the assumption that the different amounts be fairly and judiciously expended.. Books will show an amount of expenditure of money, but the condition of the stock can alone show whether talent and prudence have been exercised in the appropriation of it, and on this account I submit, that it is the bounden duty of every board of Directors, to have an annual valuation, if not of all their floating locomotive stock, at least of each engine specifically; and, furthermore, I contend that the character of locomotive superintendents generally, is somewhat compromised by their not insisting on such valuation being made.

Let us suppose, then, that an engine of the best manufacture, say £2500, was newly set to work on the 1st of January, 1849, and that either the same engine must stand ready for work newly repaired, and in no single respect inferior in effective value on the 1st of January, 1859; or that she be worked to an extremity during the coming ten years; sold at the end of that time for what she would fetch, and a new one precisely similar, stand ready to take her place. I will first comment upon the latter supposition, viz., that it be the intention of her owners to replace her with a new one in ten years, and consequently to get as much work out of her as possible during that period, at the lowest possible current cost.*

Assuming, then, that by extraordinary good luck she runs 300,000 miles in the ten years, as follows-140 miles per day, five days every week, or in round numbers 3000 per month, for the first twenty months up to the 31st of August, 1850. This would give a total of 60,000 miles every two years, allowing the last four months to refit her for commencing work again. And in addition to this we have an allowance of two days every fortnight for overhauling and casualties.‡

Upon the above distance, viz., 300,000 miles§, let us suppose 2d. per

* 2d. per mile named in my prefatory remarks, is, I believe, the lowest quotation for repairs that has yet been exhibited.

Taking into consideration the various sources of interruption which occur to retard thorough repairs, four months would be found not too much time to make her fit to resume her station.

She may either rest one day a week, two days together every fortnight, or four days a month, as convenient, but an average of one day a week will not be found too much in the aggregate.

§ Having proposed to show calculations on an extreme, and also on a more moderate distance run, I have adopted 300,000 miles as an extreme. I don't believe any engine ever did run that distance in ten years. I don't deny the possibility of its being done, but it would require a special qualification, and would absorb more time and care than could be devoted practically to any one engine. I have assumed it in order to give every advantage to the low figure of 2d. per mile for repairs.

mile appropriated to repairs. Now, in repairs there are two specific items of the most expensive nature, which cannot be set aside, viz. fire-boxes and tubes,* as upon the perfect state of these depends the entire well-doing of the engine, or nearly so. I will, therefore, first make a specific charge

for these.

I consider that with the above named hard work an engine would require, at least, a new set of tubes every two years, or 60,000 miles,† and a new fire-box, say at the end of every four years. We have, therefore, to debit our engine with the cost of two new fire-boxes in the ten years, and four sets of new tubes, viz. a set at the end of the second, fourth, sixth, and eighth years, the last set of which would keep her going till the end of the tenth year, when we have assumed she would be sold. The account will then stand thus:

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Thus showing a clear demand of 44 per cent. on the amount allowed for repairs of engine and tender for ten years, and leaving a balance of only £1400 for general purposes. A moment's consideration of the costliness of many other specific items, viz., wheels and axles of both engine and tender, cylinders, pistons, &c., besides the innumerable smaller matters which are involved in a thorough repair, to say nothing of a due share of general charges,¶ will render the utter inadequacy of the above sum too palpable to require any comment.**

I will, therefore, (still giving her credit for doing the above extreme amount of work, say 300,000 miles,) assume that 24 d. per mile be allowed for repairs during ten years; that she have a thorough repair every two years for eight years, and at the end of ten years she is to be offered for sale.ft

Whatever other repairs may be neglected or delayed, these two must be kept up. The loss of power from a defective boiler is incalculable.

† Few tubes do run this distance even with the best of coke.

A new tube plate is sometimes introduced as a temporary relief to fire-boxes, but considering the expense of taking out and putting in, I think it the best economy to renew the whole box, as we have the old metal to our credit, and a really good job cannot be made of staying the sides of an old box the second time.

$ Tubes are taken at the set of 200 in number, 11 feet 6 inches long, and 2 inches outside diameter. These will cost at least 288. per tube, delivered at the Company's works, and I allow £20 per set for ferrules and putting in. New fire-boxes are assumed at 26 cwt. of copper, at 11d. per lb., and allows about £ 45 for making and putting in.

Old tubes are taken at one-fourth their original value, viz., half-price, less diminution of weight of 33 per cent. or more, and the expense of taking out and back carriage. Old fire-boxes allowed half their original cost.

¶ General indoor charges include stationary engine for driving machinery, repairs to machinery, tools, and buildings; rates, superintendence, foremen and clerks, gas, &c. **It is evident that, even if kept alive at all, she would work at a great sacrifice of power, &c., and be utterly unsaleable at last.

tt Be it remembered that being now, as it were, "used up," any purchaser would be necessitated to lay out an extravagant sum to make her available.

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Now, supposing that she actually runs twenty months at a time, and at the end of each period has a thorough repair, it will be necessary in the division of the above sum of £2025, to vote £100 or thereabouts, to be expended during each period of running for casualties.*

Taking a low allowance, let us say for the ten years 4251. This leaves a balance of 1600l. to be divided into four thorough repairs of engine and tender, and at the end of the last two years she is to be unhooked from her last load, drop her fire, and be offered for sale. If a purchaser be found at all, she might probably fetch 400l., certainly not more,† and I appeal to any man experienced in such things, whether, after her great amount of work done and limited allowance for repairs, the above sum be not a handsome one.

Assuming this to be the result of ten years' work at an allowance of 23d. per mile for repairs, our account will stand thus:

By sale of old engine,

Reserve required of 14d. per mile beyond current expenditure on
300,000 miles,

Assumed bank interest on accumulating reserve fund at 23 per cent.‡

£ 400

1875

225

£2500

Required to pay for the new engine which is to succeed the old one on the 1st January, 1859.

We therefore see that, under the most favorable circumstances, a sum of 4d. per mile run must one way or other be appropriated, if old engines are to be periodically replaced by new ones,§ or a gross cost of 50002., taking advantage of interest on accumulating money.

It being evident, therefore, that, with an extreme amount of mileage, a current charge must inevitably be made on revenue of at least 4d. per mile run, if the renewing system be adopted, let us see the demand on our revenue under the circumstances, supposing it were our intention to maintain the same engine, and have her fully repaired and ready to

These casualties are the ordinary small jobs which each working engine requires, and must have done, and for which the average time of one day per week is allowed. I have taken no account of serious accidents, which the whole world knows are often very expensive, and which must continue to occur occasionally to the end of time. I consider that the expenses of a serious accident to any one engine should be put to the account of "general charges," and be proportionately borne by all. All are liable to accident, and all should help to relieve.

I say this from having had some experience in the sale of worn out engines, and it is not unlikely she might have to wait many months before such a sum, or even a less sum, could be got for her.

I fear few Companies would be found to have been so prudent as to take advantage of this interest on accumulating money.

§ Not having to devote the last four months of the ten years to repairs, it may be argued that an extra quantity of work might be obtained from the engine in the given time. I maintain that her condition would be such that she would barely complete the 60,000 miles in the last two years, including the extra time. If she realized any excess, it might be placed to the relief of bank interest, for if the amount allowed for this were not realized, it would require an extra charge of nearly 4d. per mile on 300,000 miles to make up the difference.

commence a second ten years work on the first of January, 1859. The specific repairs of fire-box and tubes will in this case bear a different proportion, and instead of two fire-boxes and four sets of tubes, I must here charge the engine with two and a half fire-boxes and five sets of new tubes,* making, after allowance for old metal, a demand of 13751. for these two items alone. In addition to this I will allow a clear charge of 1007. for each period of twenty months' running, to be expended in casualties, or a gross charge for ten years of 500l.,† and instead of four thorough repairs at 4001. each, I will give 2500l. to be divided into five thorough repairs, (the last, of course, being done between the 1st September, 1858, and 1st January, 1859,) say four repairs at 450l. each. At the end of the second, fourth, sixth, and eighth years respectively, and a clear 700l. to cover all at last, exclusive, of course, of fire-boxes and tubes charged before.

This shows our account to result as follows:

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Or a gross cost of 43751. on 300,000 miles, averaging a charge of under 34d. per mile, being d. per mile less than in the case of buying a new engine.

This difference of d. per mile on 300,000 miles makes a gain of 6251. per engine to the Company every ten years.§

To be Continued.

A Flue of Flues.||

In course of operations in the Tamar Silver Lead Mines, on the borders of Devon and Cornwall, it became latterly essential either to erect a powerful steam engine at the foot of a subterranean inclined plane, 2000 feet in length, and running right below the river which flows over the mine, to a perpendicular depth of 800 feet below its bed; or, failing that, to shut up the mine and throw 1500 people out of employment. It was, therefore, determined to adopt the former alternative, and a 20-horse steam engine, one of the patent combined hydraulic engines from Walker's

The fire-box being removed at the end of each four years, would leave one only “half worn" at the end of ten years, into which a set of new tubes would be put. I therefore debit her half of the value of a third box, and take credit for half the value of old metal accordingly.

In the renewing system I only allowed £425 for casualties. In this case I give a more liberal allowance, knowing well the value of constant care or "a stitch in time.”

I believe the most punctilious could not deny that, with an annual allowance for casualties in repairs of £ 60, and a provision of £450 every twenty months, (exclusive of fireboxes and tubes,) for thorough repairs, £ 700 would well refit her, and turn her out in as effective a state as at first, if not better.

§ This §d. per mile in a stock of two hundred engines will be equal to £125,000 in ten years, or £12,500 per annum, which ought and eventually must be charged to revenue. From the London Builder, November, 1850.

manufactory at Oliver's yard, City-road, was accordingly fitted up at that depth. Flues were, of course, requisite, and it was found advisable to conduct these across to the furthest bank of the river, and in a series of horizontal levels united by perpendicular shafts, so that the flue in sections rises like a flight of stairs to the surface. This flue is no less than two miles long and upwards, probably the longest flue in the world. The result was quite successful, as will appear from the following statement: "We drew through Spurgin's shaft in October month 2988 kibbles of stuff with Walker's new underground engine: this machine is well constructed, and I have every reason to believe she will pump the shaft 150 fathoms deeper than it is at the present time. We have in these mines six steam engines at work at the surface, but the draft of the under-. ground engine exceeds the whole. The consumption of coals is 5 cwt. in the twenty-four hours."

Ship Canal between the Mediterranean and the Red Sea.*

Mr. Robert Stephenson is now on his way to Suez, to examine the route for a ship canal between the Mediterranean and the Red Sea. This survey is said to form part of a conjoint survey directed by England, France, and Austria, the former being represented by Mr. Stephenson, France by M. Paulin Talabot, and Austria by M. Negrelli. These latter have completed their labors, and on the completion of Mr. Stephenson's survey, the route will be determined on the conjoint evidence of the three reports. It is hoped the three powers will contribute the funds, if not the works will be conceded by the Pasha to a Joint Stock Company. Before the Academy of Sciences the survey of M. Bourdaloue, made in 1847, has been laid; it was under the direction of Mehemet Ali Pasha, and embraces the country between the Nile and the Red Sea, the levels being most carefully taken. The results differ very much from those of the French Commission of 1799.

The Bridge Failure at the South-Eastern Station, London Bridge.†

Experience is only true and valuable so far as it is on an extended basis, for, though called so, that is not experience which is merely local and partial. We are not always called upon to reproduce the same model or work on the same lines; but our practice is chiefly in the extension or particular application of existing examples. It therefore becomes of the greatest importance that we should have as wide a collection of facts as possible, so as to enable us more safely to calculate the result of any new direction, new application, or further extension; so, indeed, as to secure us from experimenting too far. We want, therefore, not only examples of success, but of failure; we want especially to know where any principle has been strained too much, that we may avoid such extreme, and where any detail has proved defective, so that we may apply the proper remedy. It has therefore always been considered, by our best authorities, as most expedient to record failures. Thus Smeaton prefaces the history of the Eddystone Lighthouse; thus, in the history of the Menai Bridge, the checks

* From the London Architect, for November, 1850. Ibid.

VOL. XXI.-THIRD SERIES-No. 2.-FEBRUARY, 1851.

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