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Report by Mr. Brunel, recommending its Adoption on the South Devon Railway (August 19, 1844)

Mr. Brunel also was summoned as a witness. Previously to this time he had taken a great interest in the various attempts which had been made to introduce the Atmospheric System, and he had himself conducted experiments at Wormwood Scrubs and at Dalkey. As early as July 1840 he had considered its applicability to the Box Tunnel incline on the Great Western Railway. He had also considered it in reference to various projected lines; and in 1843 he recommended it for adoption in a long tunnel on one of the steep inclines of the Genoa and Turin Railway, the success of the system being then (he wrote) sufficient to justify its use on a part of the line protected from weather. It was not, however, applied on this railway. [1]

Mr. Brunel’s views at this time are indicated in the following letter:—

April 8, 1844.

Any part I have taken in examining into the system has been purely from the desire which I always feel to forward good inventions; and when I have formed a decided opinion, no fear of the consequences ever prevents my expressing it. My great anxiety, however, is to see a line of railway and all its appurtenances made expressly for the Atmospheric System, and worked accordingly; until this is done the results will be comparatively unsatisfactory.

Although unwilling to express general opinions, Mr. Brunel spoke strongly before the Croydon and Epsom Railway Committee in favour of the advantages of the Atmospheric System under certain circumstances, and approved of its use on that line.

A few months later Mr. Brunel recommended the Directors of the South Devon Railway Company to adopt the Atmospheric System, and they resolved to act on his advice.

His report was as follows:—

August 19, 1844.

I have given much consideration to the question referred to me by you at your last meeting—namely, that of the advantage of the application of the Atmospheric System to the South Devon Railway.

The question is not new to me, as I have foreseen the possibility of its arising, and have frequently considered it.

I shall assume, and I am not aware that it is disputed by anybody, that stationary power, if freed from the weight and friction of any medium of communication, such as a rope, must be cheaper, is more under command, and is susceptible of producing much higher speeds than locomotive power; and when it is considered that for high speeds, such as sixty miles per hour, the locomotive engine with its tender cannot weigh much less than half of the gross weight of the train, the advantage and economy of dispensing with the necessity of putting this great weight also in motion will be evident.

I must assume also that as a means of applying stationary power the Atmospheric System has been successful, and that, unless where under some very peculiar circumstances it is inapplicable, it is a good economical mode of applying stationary power.

I am aware that this opinion is directly opposed to that of Mr. Robert Stephenson, who has written and published an elaborate statement of experiments and calculations founded upon them, the results of which support his opinion.

It does not seem to me that we can obtain the minute data required for the mathematical investigation of such a question, and that such calculations, dependent as they are upon an unattained precision in experiments, are as likely to lead you very far from the truth as not.

By the same mode M. Mallet and other French engineers have proved the success of the system; and by the same mode of investigation Dr. Lardner arrived at all those results regarding steam  navigation and the speed to be attained on railways, which have since proved so erroneous.

Experience has led me to prefer what some may consider a more superficial, but what I should call a more general and broader view, and more capable of embracing all the conditions of the question—a practical view.

Having considered the subject for several years past, I have cautiously, and without any cause for a favourable bias, formed an opinion which subsequent experiments at Dalkey have fully proved to be correct; viz. that the mere mechanical difficulties can be overcome, and that the full effect of the partial vacuum produced by an air-pump can be communicated, without any loss or friction worth taking into consideration, to a piston attached to the train.

In this point of view the experiment at Dalkey has entirely succeeded. A system of machinery which even at the first attempt works without interruption and constantly for many months, may be considered practically to be free from any mechanical objection.

No locomotive line that I have been connected with has been equally free from accidents.

That which is true for one railway of two miles in length is equally true for a second or third, although they may be placed the one at the end of the other; the chances of an accident are only in the proportion of the number, or in other words, the length, a proportion which holds equally good with locomotives, except that a locomotive may be affected by the distance it has previously run, while a stationary engine and its pipes cannot in like manner be affected by the previous working of the neighbouring engine and pipes.

In my opinion the Atmospheric System is, so far as any stationary power can be, as applicable to a great length of line as it is to a short one.

Upon all these points I could advance many arguments and many proofs, but I shall content myself with saying that, as a professional man, I express a decided opinion that, as a mechanical contrivance, the Atmospheric apparatus has succeeded perfectly as an effective means of working trains by stationary power, whether on long or short lines, at higher velocity and with less chance of interruption than is now effected by locomotives.

I will now proceed to consider the question of the advantage of its application to the South Devon Railway.

It will simplify the discussion of the question very much if it is considered as a comparison between a double line worked by locomotives in the usual manner, and a single line of railway worked by stationary power, the only peculiarity of the present case being that upon four separate portions of the whole 52 miles stationary assistant power would under any circumstances have been used, these four inclines forming together one-fifth of the whole distance.

It is necessary to consider it as a question of a single line on account of the expense, the cost of the pipe for each line being about 3,500l. per mile.

An addition of 7,000£ per mile, or of about 330,000£, in the first construction could not be counterbalanced by any adequate advantage in the saving in the works on the South Devon Railway, and probably not by any subsequent economy or advantage in the working; but the system admits of the working with a single line, without danger of collision, certainly with less than upon a double locomotive line. And I believe also that, considering the absence of most of the causes of accidents, there will even be less liability of interruption and less delay in the average resulting from accidents than in the ordinary double locomotive railway.

By the modification of the gradients and by reducing the curves to 1,000 feet radius where any great advantage can be gained by so doing, and by constructing the cuttings, embankments, tunnels, and viaducts for a single line, a considerable saving may be effected in the first cost.

In the permanent way and ballasting, the reduction will be about one-half. I should propose to make the rails about 52 lbs. weight and the timber 12 × 6; the quantity of ballast would probably be rather more than half, but at the present prices of iron and timber the saving could not be less than 2,500£ per mile.

From a careful revision of the works generally, I consider that a reduction may be effected in the following items, and to the amount specified in each, viz., ballasting gradients and curves:—

£ s. d.
Reduction in earth work 16,500 0 0
“in length of principal tunnel 14,000 0 0
30,500 0 0
Saving by single line.
Earthwork 25,000 0 0
Tunnels 11,500 0 0
Viaducts 15,000 0 0
Permanent way and ballast.
To allow for sidings, say 50 miles, 2,500l. 125,000 0 0
207,000 0 0
Per contra.
Pipe on 41½ miles [2] 138,500
Increase on inclined planes, 10½ miles 6,500 £ s. d.
145,000 0 0
Engines for the 41½ miles 35,000 0 0
Patent right, say 10,000 0 0
190,000 0 0
The difference in first cost therefore is 17,000 0 0
To this must however be added the cost of the
locomotive power, with its attendant expenses
of engine-houses, &c., which cannot, I think,
be put at less than
50,000 0 0
Making a saving of 67,000 0 0

I have not included in the expense of the Atmospheric apparatus that of the telegraph, because at its present reduced cost of 160£ per mile I am convinced its use would repay the outlay in either case.

It would appear, then, that the line can be constructed and furnished with the moving power, in working order, on the Atmospheric System, for something less than the construction only of the railway fitted for the locomotive power, but without the engines; and that taking into consideration the cost of locomotive power, a saving in first outlay may be effected of upwards of 60,000£.

But it is in the subsequent working that I believe the advantages will be most sensible.

In the first place, with the gradients and curves of the South Devon Railway between Newton and Plymouth, a speed of thirty miles per hour would have been, for locomotives, a high speed, and under unfavourable circumstances of weather and of load, it would probably have been found difficult and expensive to have maintained even this; with the Atmospheric, and with the dimensions of pipes I have assumed, a speed of forty to fifty miles may certainly be depended upon, and I have no doubt that from twenty-five to thirty-five minutes may be saved in the journey.

Secondly, the cost of running a few additional trains so far as the power is concerned is so small, the plant of engines, the attendance of engine-men, &c., remaining the same, that it may almost be neglected in the calculations; so that short trains, or extra trains with more frequent departures, adapted in every respect to the varying demands of the public, can be worked at a very moderate cost. I have no doubt that a considerable augmentation of the general traffic will be thus effected, by means which with locomotive engines would be very expensive, and frequently unattainable, particularly as regards one class of short trains, whether for passenger or goods, which from the inconvenience of working them by locomotives are hardly known—I refer to trains between the intermediate stations.

By many means, which the easy command of a motive power at any time, at every part of a line, must afford of accommodating the public, I believe the traffic may be increased.

It appears to me also that the quality of the travelling will be much improved; that we shall attain greater speed, less noise and motion, and an absence of the coke dust, which is certainly still a great nuisance; and an inducement will thus be held out to those (the majority of travellers) who travel either solely for pleasure, or at least not from necessity, and who are mainly influenced by the degree of comfort with which they can go from place to place.

Lastly, the average cost of working the trains will be much less than by locomotives.

With the gradients of the South Devon Railway, and assuming that not less than eight trains, including mail and goods trains, running the whole distance, and certainly one short train running half the distance, be the least number that would suffice, I think an annual saving of 8,000£ a year in locomotive expenses, including allowance for depreciation of plant, may very safely be relied upon.

For all the reasons above quoted, I have no hesitation in taking upon myself the full and entire responsibility of recommending the adoption of the Atmospheric System on the South Devon Railway, and of recommending as a consequence that the line and works should be constructed for a single line only. [3]

[1] This was almost the only case in which Mr. Stephenson approved of the application of the System.

Before the Croydon and Epsom Committee, in answer to the question, ‘Does the Atmospheric railway give you any power of using practically and usefully steeper inclines than the locomotive railways?’ Mr. Stephenson said, ‘Yes, I think it does, but still at a very inordinate loss of power; still it is within the scope of the Atmospheric System under particular circumstances. I remember a case where it might be advantageous. Mr. Brunel went to Italy for the purpose of laying out a line there, and from Genoa over the Apennines he had to form a line; it would probably rise 15 or 20 miles at 1 in 100 or 1 in 60 or 70. Where there is that continuous line of ascent, where no stoppages are required, where the locomotive is totally inapplicable, there I can conceive nothing more eligible than the Atmospheric plan’ (p. 80).

[2] The length of the line was 52 miles, but as it was considered that auxiliary stationary power would in any case be necessary on the 10½ miles of very steep inclines, the cost of the Atmospheric apparatus is taken on 41½ miles.

[3] It must be remembered that beyond the South Devon Railway was the projected railway through Cornwall, which, with its long and heavy gradients, was, in all its features, even more suitable than the South Devon for the application of the Atmospheric System. Had that system succeeded, and been introduced on the Cornwall Railway, a very great saving might have been made in the cost of the works of this line.

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