another, the engine (always exerting the same power) will of its own accord accelerate the velocity of the drum and increase the rarefaction, for the power applied being the same, the effect will be commensurate in the quantity of air discharged, the amount of rarefaction attained, or both combined.

The machine is an entirely new modification of the fan. Its construction is of the most simple integral character; it has no valves or separate moving parts: has no attrition, and all the friction is resolved into a foot pivot moving in oil; when at rest offers no impediment to air ascending from the shaft, is very inexpensive, and liable to no derangement; in short, it is a simple mechanical implement, whereby any degree of rarefaction necessary to ventilation is rendered certain and regular, being subject to the law of central forces, which is as fixed and determinate as that by which a stone falls to the earth.

* We make no doubt whatever that Mr. Brunton honestly believes this apparatus to be as "entirely new" in its construction as his application of it to mining purposes unquestionably is, but if he will refer to our Journal for September 16th, 1848, he will find a description there given of an exhausting apparatus then recently patented by Mr. Lloyd, which, to our thinking, differs in no material respect from his own.-ED. M. M.

In contracting it with the furnace, it may be further observed, that it is subject to no sensible difference upon the changes of the barometrical column, but, on the other hand, is capable by increase of velocity at such seasons of obviating or counteracting the danger connected therewith, and is equally applicable to all depths.

There will be no necessity for the separate conveyance of air by a stone drift into a higher part of the upcast shaft as practised to avoid the furnace.

All the injurious effect upon the iron in the upcast shaft will be entirely prevented, and no part of the workings need be stinted of air as to quantity.

By increasing the velocity of the machine during the absence of the workmen, the stagnation and danger referred to in page 13 would be prevented.

But beyond the ordinary requirements of ventilation, as now practised, there is an advantageous application of this machine, which can in no respect be effected or imitated by the furnace. It possesses such power of rarefaction that the atmosphere of a colliery may be subjected in half an hour to an artificial exhaustion of 3, 4, or 5 tenths of an inch of mercury, producing in the colliery, during the absence of the workmen

and their lights, the very same exudation of the gases that would have taken place during the natural change of the atmosphere indicated by a like fall of the barometrical column; and before the men re-enter the mine the machine will discharge the noxious gas by a current of fresh air more copious and effective than can be produced by any other means in use. All that is needful to effect this is, upon the retirement of the workmen and their lights, that the air be prevented entering the workings from the downcast shaft, the exhaustion alluded to will immediately commence; for, the quantity of air ascending the upcast shaft being decreased, the drum will be accelerated, and the whole extent of the workings will thus be subjected in a few minutes to the full measure of rarefaction obtained in the upcast shaft; upon the fresh air being permitted to enter, the colliery will be found in a state of extraordinary purity of atmosphere, and freedom from the risk of explosion.

It is the concurrent testimony of all intelligent underground men that the fire-damp exudes copiously during the fall of the barometer, and also that during its rise the reverse takes place; the fissures that during the fall were discharging gas, now absorbs or draws in atmospheric air; bat the effects attendant upon a fall of the barometer must necessarily be more or less dangerous in proportion to the time it has been rising or nearly stationary, when a large portion of the gas evolved during that period will have accumulated in the goaf basins or vaults. The nature of this is so well described in the Report of Messrs. Lyell and Faraday, upon the explosion at the Haswell Colliery in 1844, that I have requested, and obtained permission to make the following extracts; but the whole of that document deserves the attentive perusal of every coal miner.

"The goaf may be considered as a heap of rocky fragments rising up into the vault or cavity from which it has fallen, perhaps nearly compact in the parts which are the oldest, lowest, and nearest the middle, but open in structure towards and near its surface, whether at the centre of the goaf or at the edges; and the vault or concavity of the goaf may be considered as an inverted basin, having its edge coincident with the roof of the mine all round the goaf.

"Let us now consider this goaf as a receptacle for gas, or fire-damp, a compound of hydrogen and carbon, known as light hydrocarbonate, and by other names. The weight of pure fire-damp is little more than half that of air; it gradually and spontaneously mixes with air, and the weight of any mixture is proportionate to the quantities of air and fire-damp. Any gas that

may be evolved in the goaf, or that may gradually creep into it along the roof of the workings, against which it will naturally flow, will ascend into the goaf vault, and will find its place higher in proportion to its freedom from air; and this will go on continually, the goaf vault forming the natural basin into which all gas will drain (upwards) from parts inclining to the goaf, just as the concavity on the side of a gentle hill will receive water draining downwards from its sides, and from the parts above inclining towards it.

"Thus goafs are evidently in mines subject more or less to fire-damp, reservoirs of the gas, and explosive mixtures; giving out their gas into the workings of the mines by a gradual underflow in smaller or larger quantities under ordinary circumstances, or suddenly, and in great proportion, on extraordinary occasions; and they may either supply that explosive mixture which first takes fire, or they may add their magazine of fire-damp and explosive mixtures to increase the conflagration when the fire reaches them from an explosion in some other parts of the mine.

"There is one other point connected with what may be called the action of the goaf, and the occasional, sudden, and temporary discharge of gas from it. One of the witnesses on the inquest, Mr. G. Hunter, pointed out the effect he had observed in the mine on a change in the barometer,— that as the barometer fell fire-damp would tend to appear, and that it did this the more suddenly and abundantly if the barometer, having continued high for some time, fell suddenly; and Mr. Buddle has already strongly stated his opinion that accidents from fire-damp always occur with a low barometer.

"A fall of an inch in barometer, of a sudden, is rare, but a fall of one-tenth of an inch is not, and that in such a goaf as the one supposed, viz., 13 acres, would place 7,550 cubic feet below the edge of the cavity; this all tends to issue forth at one place, and that generally a place where the ventilation is weakest. Hence it does appear to us that the goaf, in connection with barometer changes, may in certain mines be productive of sudden evolutions of fire-damp and explosive mixtures, and that the indication of the barometer, and the consequent condition of the mine, ought to be very carefully attended to."

From these observations, it is obvious that if the fire-damp be drawn off at short intervals, as at every twenty-four hours, the accumulation and consequent danger will be very little compared with what it frequently is through the continuance of weeks of fine

ened, for the purpose of steadiness. When again placed on the rails, the machine acquired a speed of 20 miles per hour, but the original axis being too small for the increased weight, the crank axle was strained in passing through the points, and the machine was taken back to be refitted with axles of a larger size. When again taken out of the shop, the machine was of the following proportions:

Cylinder, 3 inches diameter, 6 inches stroke.

Diameter of all four wheels, 3 feet 4 inches.

Boiler, 1 foot 7 inches diameter, 4 feet 3 inches in height.

Tubes, 1 inches diameter, 3 ft. 3 in. long. Total heating surface, 43 feet long. Distance from centre to centre of wheels, 9 feet 6 inches.

Tank, to contain 40 gallons of water; seats for 7 passengers.

[Mr. Samuel here exhibited engravings taken from Mr. Weale's new edition of "Tredgold on the Steam Engine," showing a plan, side elevation, and section of the "Express" Locomotive Carriage, as it was then called.]

The extreme steadiness of the engine when travelling at high speeds, was remarked by many who have had an opportunity of running on her; this was to be attributed principally to the lowness of the centre of gravity, the frame being suspended from the axles.

The engine has run altogether about 15,000 miles, and the consumption of coke has been about 3 lbs. per mile; but the construction of the boiler is not such as to give the most economical results, although extremely convenient for the small amount of space required.

The greatest speed attained by this engine on the level was 51 miles per hour, but of course she could not maintain it. The ordinary speed that might be safely calculated upon for a long journey, was 30 miles per hour on one occasion, she performed the journey from London to Cambridge, a

distance of 57 miles, in 14 hours, with a consumption of coke 2 lbs. per mile.

While the express engine just described was developing such satisfactory results, Mr. Adams and the writer had meanwhile been speculating on the desirability and applicability of steam carriages to the purpose of expresses, and also for working branch railways. After much consultation, the writer came to the conclusion that it was quite practicable, and an examination of the return, kept by the Company as to the traffic on the branch lines, showed him that the actual number conveyed by each train was under 50, the highest average being 47, and the lowest average being 10, and that the disproportion between the gross load of the train and the paying load, or the weight of the passengers, was enormous. In fact, it appeared from these returns, that the dead weight was to the paying weight as 24 is to 1, that is, 24 tons of engines and carrriages were employel to convey 1 ton of passengers!

It appeared to be this disproportion which, in large trains, necessitated the use of large engines (so large, indeed, that they defeat the very object for which they are constructed), because their extreme weight crushes the rails and the joints to such an extent that, practically, the railroad becomes a worse road, quoad the engines travelling on it, than an ordinary Macadamized road is to a stage-coach.

The object of the present paper is to show that the locomotives now in use on most of the railways have outgrown the wants of the passenger traffic, and that the weight on the driving wheels, amounting in some cases to 14 tons, is perfectly unnecessary for the number of passengers conveyed in ninetynine cases out of a hundred.

The subjoined statement shows the actual number of passengers conveyed on the Eastern Counties Railway, both main line and branches, by each train for the week ending 7th May, 1849.

The Return shows the highest number in each train at any one time :