have either never yet built a carriage, or whose carriages when built have never stirred out of the factory yard!

Sir.-Tuesday evening, the 20th inst., completed twenty weeks continued running on the Stratford, Islington, and Paddington roads, during this year, and I beg to hand you as faithful an account as I can of the performances of my carriages.

Since the last notice in your Magazine, a new carriage, the "Automaton,” has been brought upon the road, the only difference between which and those preceding it is, that the engines are of greater power (having cylinders of twelve inches diameter, whilst those of the others are of nine inches,) and the carriage altogether of larger dimensions than the others, it having seats for twenty-two, whilst they are only calculated for fourteen passengers. It is an open carriage like the "Infant;" and although only calculated for the accommodation of twenty-two passengers, it has carried thirty at one time, and would then have surplus power to draw an omnibus or other carriage containing eighteen more passengers, without any material diminution of speed; its general rate of travelling is from twelve to fifteen miles per On one occasion it performed (when put upon the top of its speed, and loaded with twenty full grown persons) a mile on the Bow-road, at the rate of twenty-one miles per hour.

The first time the "Automaton" was brought upon the road, (the latter end of July) it conveyed a party to Romford, and back, at the rate of ten to twelve miles per hour, without the least interruption or deviation in its working, although it was the first, or as I may call it, the day of proving, nor has it required any repairs whatever to this time.

After this digression in describing the "Automaton," I will return to the actual work done on the public roads and streets of the metropolis during the last twenty weeks, or five months, in as concise a manner as I can:

20,420

Supposing the carriage had always been full, the passengers

Average time a carriage has run each day-5 hours 17

minutes.

An exact account of the number of times that the carriages have gone through the city in their journeys has not been kept, but I should suppose that it must be more than 200. For the last five weeks a carriage has been at the Bank twice a day, viz. between the hours of 2 and 3 and 5 and 6 in the afternoon.

It was on one of the morning trips from Stratford to the Bank, through the city, that the steamer became entangled with a waggon at Aldgate; and which, I am happy to say, is the only accident worth recording. The shafts of the waggon were swung by the contact, against the projecting front of a shop; the damage done was trifling, and occasioned by the wheels of the steam carriage having got into the iron gutter, and out of which it is not an easy thing to gain the fair surface of the street with any ordinary car. riage in so confined a situation as that part of Aldgate in which the accident happened; and it should be observed, that this occurred in making way for another carriage passing at the time.

I will now give you an account of all other accidents (which have all happened to the damage of the steamers themselves,) viz. the chain pulley of the "Enterprize" once broke on the axletree; the same occurred once to the "Infant," which were permanently and immediately replaced by castings from the same pattern, with a greater thickness of metal, and which have since stood well.

The severe test afforded by the state of the City Road and onward to Paddington, caused these failures, for the pulleys had stood well on the other roads, for many miles.

Another accident was a hind-wheel of the "Erin" coming off in the New Street, near the Bank, on which occasion the carriage sunk only about eight or nine inches, in consequence of the frame-work of the machinery taking the ground; and so little was the coach thrown out of the level, that the inside passengers were surprised when informed that the wheel was off. The concluding accident was by the steerage chain of the "Infant" being too slight, and breaking at Islington, when the carriage turning short round, with one of the fore wheels against the curb, the wheel was broken. This wheel was an old one, of much slighter construction than I now make them.

In the early part of the five months' running, the close-bodied carriages, "Erin" and "Enterprize" were about equally employed-in the latter part, and to the present time, in consequence of the fine weather, the open carriages "Infant" and "Automaton" have been running.

I have occasionally examined the boilers and engines of all the carriages, and found that the engines have in most parts actually improved, whilst the boilers and fire-places have suffered a deterioration, less than could have been expected, from the use they have undergone.

It may be remarked, that both boilers and machinery are suspended on well-acting springs, and which accounts for the state of all the parts being so well preserved. Some of the boilers have been in use for two or three years.

There have been consumed in the before mentioned traffic, 55 chaldrons of coke, which is equal to 76 miles per chaldron, or about 2 d. per mile for fuel; but this on long journeys would be much reduced by the application of the moveable fire-place, patented by me about three years ago, as our greatest expenditure of coke in these short journeys is in lowering and again raising the fire.

I cannot conclude without noticing with gratitude, the general civility and attention which I have met with, and my pleasure in discovering that the antipathies which existed in the earlier part of my career are gradually subsiding, and that, in fact, I never now meet with incivility, excepting with a few carters or draymen, who consider the introduction of steam-carriages as an infringement upon the old established use of horse flesh.

Years of practice have now put all doubts of the economy, safety, and superiority of steam travelling on common roads at rest, when compared with horse travelling; and I have now in preparation calculations founded upon actual practice, which when published will prove that steam-locomotion on common roads is not unworthy of the attention of the capitalist, though the reverse has been disseminated rather widely of late by parties who do not desire that this branch of improvement should prosper against the interests of themselves.

After twelve years of incessant labour in steam-locomotion, yours, &c. WALTER HANCOCK.

Stratford, Sept. 22, 1836.

Lond. Mec. Mag.

Anti Attrition Compound. To one part of lime water (a saturated solution of lime) add one part of olive oil, unite them well by thorough stirring or agitation, and they form a soapy compound of the consistence of cream. If too weak for the purpose, more oil may be added. This compound is said to be better than pure oil for the lubrication of small works. For cogs or teeth of wheels, whale or common oil may be taken in the proportion of one part to two of lime water. It assumes the consistence of thick paste, when a small quantity of carbonaceous matter, such as plumbago, or soot, may be added and well incorporated.

For this compound a patent was taken out in England, by N. Partridge, in December, 1835.

Lon. Jour. Arts and Sciences.

Lubrication by Water. Sir,-I perceive in the report, of the Times, of the proceedings of the scientific meeting at Bristol, that Dr. Lardner suggests placing water-pots before the wheels of a train of railway carriages to reduce the friction. The fact of a train running lighter on a wet day is well known to every engine driver; and it occurred to me to avail myself of the water leaking from the boiler, or tender, passing it, in the first instance, into the ash-pan, from which the excess drops in a small jet behind the engine wheels; thus the engine passes over the dry, and the tender and train over the wetted part of the rail. In the event of the boiler being so tight that the leakage would be insufficient, two small tubes, with regulating cocks, should pass from the tender, or cistern, and discharge a small jet on the rails as the train passes along. I shall feel obliged by your insertion of this letter in your earliest Number, in order to advance my title to the priority of this useful adaptation of what would be otherwise lost water. Yours, &c. W. J. CURTIS.

Progress of Civil Engineering.

Traction on Rail-ways.

Lon. Mec. Mag.

From an article in the Dublin Review, No. 1, (May, 1836) on "The Rail Road System

in Ireland."

A modern Railway may be defined to be a perfect Road-hard, dry, and level, presenting the least possible resistance from irregularities of surface or inclination. Vehicles properly contrived, and furnished with wheels and axles, peculiarly constructed to move along the iron tracks with the least friction; and the untiring mechanical engine, compressed into the smallest useful compass, mounted on a carriage, supplied from a portable boiler, with steam at a high pressure, and yoked in front of the frame to be moved, give forth an irresistible power, transporting passengers and merchandize with a speed and economy wholly unattainable by means of animal resources.

The force necessary to move any given load on a horizontal line, is expressed by writers on mechanics in terms of the load itself. On a Railway extremely well laid, and in good order, with the bearing perimeter of the wheels turned perfectly true; with the best fitted axles, properly lubricated, and the iron rails clean and dry, or quite wet, the friction is reduced to its lowest terms. By friction is to be understood the sum of the obstruction to the movement of the carriage or train of

carriages, arising from the resistance to the rolling periphery of the wheels as they move along the rails, and the friction at the axles from the insistent load. The amount of resistance is small, and, supposing the rails to be clean and in order, need not, by the general enquirer, be distinguished from the sum total of the friction.

Experiment has satisfactorily proved, that the friction is the same at all velocities. To overcome this friction, or, in other words, to overcome the vis inertia of the load, a certain power is requisite, varying somewhat, as will be presently shewn; but which power, on a Railway, is now usually taken to be about oth part of the load, whatever that may be. Now a ton consisting of 2240 lbs. theth part thereof is 9 lbs. nearly; and it is the ordinary expression in Railway parlance, to call the friction 9 lbs. to the ton. Some engineers prefer taking 10 lbs. to the ton, orth part of the load, as the measure of the friction, in all states of the weather, of the Railway and of the carriages. Others consider that 8 lbs. orth, or even 7 lbs, orth part of the load, to be a sufficient allowance. The above form the extremes for practical purposes; but experiments have been made on carriages, with axles so constructed, and the Railway in such good order, that the friction, in one case, appeared to be as small as 24 lbs. to the ton, or oth part of the load; and in some other instances, only 4 or 5 lbs. orth of the load. These are, however, only interesting as illustrative of what is possible, under very peculiar circumstances; but like many experiments on models, would lead to false conclusions, and be deceptive, if stated to be true in general practice.

Under all the states of road and weather, then, the exertion of a force (animal or mechanical) of 9 or 10 lbs. will move a ton upon a level Railway. Now an ordinary horse, travelling at the rate of about 24 miles an hour, and working 10 hours daily, exerts a force of about 128 lbs. This, indeed, is a point rather unsettled among engineers, and a horse-power is usually taken higher; but it is a safe average for all horses. The momentary effort of a powerful London dray horse is perhaps four or five times what is above assumed, while a weak, ill-fed animal, used through a long journey, would be scarcely equal to half the above effect. An ordinary horse can take, however, about 14 tons along a level Railway, at the rate of 2 miles an hour, working all day; but the power of an animal to draw is diminished as he is driven more rapidly. A horse capable of travelling 12 miles per hour, would only draw 3 tons on a level Railway at that velocity, and could not continue to do so any length of time.

The application of animal power is therefore very limited, and it is to steam recourse has been had, to obtain high velocities. Though it is true that the friction, and of course the power, requisite to move the dead weight, is the same at all velocities, yet the velocity itself is only obtained in the ratio with which the power to overcome the friction of the load is supplied. In a locomotive steam engine, of the best modern construction, the velocity may be defined in a general way, to be regulated by the boiler-power-that is, the capability of the boiler to supply steam, of effectively high pressure, with sufficient rapidity, so as to enable the pistons to make a greater number of strokes per minute, thereby turning the wheels round a greater number of times, and of course urging the machine to a higher speed. So the load which the same engine can draw, supposing it to have sufficient adhesion on the rails,

may be expressed to be regulated by the diameter of the cylinders, the pressure of the steam, and the length of the stroke of the piston, from which elements are obtained a certain expression of value in lbs. called the cylinder-power, which, divided by 8, 9, or 10 lbs. as the friction may be assumed, gives the number of tons which the engine is capable of drawing. This is by no means a scientific, and perhaps not a strictly correct description; but it will convey an approximate idea of the power and effect of the locomotive engine, which is all that is necessary on the present occasion.

The most remarkable circumstance in the application of steam-power on railways, is the mode in which the steam, having done its duty in the cylinders of the engine, is discharged up the chimney, and entering therein under a pressure still considerably higher than the atmospheric pressure, produces a momentary vacuum; this is followed by a rush of air from the flues or tubes of the boiler, thus creating a great draught from the furnace, and, by drawing the heated air in the increased velocity through the tubes, generates steam in the boiler with proportionate rapidity. This steam supplies the force to overcome the friction of the load with corresponding velocity, and is again quickly discharged from the cylinders into the chimney to produce the preceding effect in the increased speed. The absolute power of a locomotive engine is therefore measured by the velocity with which the engine moves; and a machine which at 15 miles an hour may be called a twenty-horse engine, at 30 miles an hour becomes a forty-horse engine. Many singular and important consequences hence present themselves to the engineer; it would lead us too far astray from our general subject to attempt to analyze them; but the practical result is, to add to the other reasons for keeping railway lines as nearly horizontal as attainable, since the velocity, and consequently the power of the engine, is greatly diminished when ascending acclivities, from several causes, particularly from the effects of gravity, upon which we shall proceed to remark.

The power necessary to overcome the friction that is to move a load, is stated in terms of the load; and so is the power requisite to overcome the effects of gravity, when the line deviates from the horizontal. The rise of any such plane is usually expressed by the proportion between the base and perpendicular of the right-angled triangle, of which the inclined plane forms the hypothenuse, being an inch, a foot, a yard, &c. vertical, to so many inches, feet, yards, &c. horizontal. Thus, a plane. which rises one foot, or any other lineal measure, in 250 feet, or any other number of lineal measures, is said to rise 1 in 250; and the expression of the power requisite to overcome the effects of gravity is s being that fraction or proportion of the load; and if the load be one ton, then the power to overcome the gravity due to a rise of 1 in 250, is nearly 9lbs. The power requisite on a rise of 1 in 224, is 10 lbs. per ton; and the power on a rise of 1 in 280, is 8 lbs. ; and on a rise of 1 in 300, about 5 lbs.; and so, by dividing the number of pounds in a ton (2240) by the number which expresses the proportion of the base to the perpendicular, of any triangle such as above, being the denominator of the fraction a table may be formed exhibiting the power per ton, requisite to overcome the power of gravity on all inclinations, to be added to the friction on ascending planes; and (to a certain extent only however) to be deducted from the friction on decending planes.

In describing the gradients of a rail-way, it is usual to state the rise