tion and not simply when it is on lap as described in the case which you cite.

Q.-F. M. K.-Will you please explain why it is that my brakes work all right in service but they release when I set the emergency? It only does this when the engine is alone. If I have it coupled to a train it stays on in service or emergency.

A.-You have only included a portion of what you do in the way of manipulating the brake valve handle, but the reason for the action you describe is as follows:

With the engine alone, when the service application of the brake is employed you take air from the equalizing reservoir, the equalizing piston rises and again seats when the brake-pipe pressure has been reduced slightly below that in the chamber above the piston, and the brake remains applied. When you apply the emergency, and it only does this when you use the " snap" emergency, you take air from the brake pipe and none from the equalizing reservoir connected with the top of the piston. If the brake valve handle is quickly returned to lap position the conditions as to pressure are as follows: Pressure has been taken from below the the piston, but that above is practically 70 pounds. This pressure of 70 pounds begins to feed slowly past the equalizing piston packing ring into the brake pipe, gradually raising this pressure. As soon as the pressure in the brake pipe is greater than that in the auxiliary reservoir the triple piston is forced to release position and the brake releases. Sometimes it is the brake on the tender that releases and sometimes that on the driver. Owing to it being customary to have the piston travel on the engine longer this brake is more likely to be the one which releases as the equalization between the brake cylinder and auxiliary reservoir is lower.

This action does not always result. The condition of the brake pipe as to leakage as well as the condition of the packing rings in the triples are deciding factors in the operations described. In either case, if the leakage were equal to the

feed by the packing ring of the equaliz ing piston there would not be a sufficient differential on the two sides of the triple piston to force it to release position. If the piston packing ring in one of the triples is in better condition than the other the one containing the better fit will release while the other will remain applied.

If necessary to use the emergency, place the brake valve handle in emergency position and allow it to remain there, in which case the release described will not Occur. With a train the valves is so great that the leakage by the equalizing piston is insufficient in volume to affect the brakes.

Q.-F. G.-I notice that two nine and one-half inch pumps are being used on a great many freight engines. I also notice that some of the new engines have one large pump. Which is supposed to be the better practice?

A. The matter of one large pump versus two smaller ones represent practices which will have to be tried out in service before it can be definitely stated which is the better. There are arguments for both practices.

If it is simply a question of which will supply the greater amount of air, there can one large pump be used which will supply more air than two of the smaller pumps. With the large pump it is customary to use the compound variety in connection with the steam cylinders or the air cylinders or both. The Westinghouse compound compounds both the steam and air and is exceedingly efficient, the New York No. 5 pump is of the duplex variety and compounds the air only. With either of these pumps an engine failure results if the pump should fail; if one of the small pumps should fail there is still one left with which to bring the train in and no engine failure is the result. This is an all important point on the larger roads and is often the deciding factor in deciding which practice is to be followed.

By using a single, large capacity pump it may be that we will revert practically to the days when one pump was capable

of doing the comparatively small amount of work required of it and still not fail between the shoppings of the engine. If this same condition is bound to result when using the more economical large pump it is very likely that this compressor will be selected on account of the steam economy effected, but if it occasionally fails it is probable that the two smaller pumps will be used as it has been found that the use of the two pumps practically does away entirely with engine failures chargeable to the failure of the air pump.

Q.-N. M.-The new engine which I have has the ET brake and it seems to hold harder than the old style brake did. I understand that it is better on account of the maintaining scheme, but it seems as if it had a better brake anyway. Is the braking power any higher with this new brake?

A.-There are so many engines in service equipped with the old style brake in which the packing leathers are in such a deplorable condition that it is little wonder that the braking power seems to be higher on an engine having the new equipment with which the leakage in the leathers does not result in a loss of power. As a matter of fact the percentage of braking power is actually less than with the old standard brake. With the old brake it is customary to figure a certain percentage of the weight on drivers or braking power based on a cylinder pressure of 50 pounds. With the new brake the cylinder pressure is figured as being 60 pounds, where but 50 pounds is obtained in a service application of the brake. In the emergency application of the brake, as described in a previous answer in this number, however, the pressure of 60 pounds is obtained, and the actual percentage of braking power figured upon is developed.

It is probable that the practice will be followed only until such time as all have become familiar with the new equipment and a brake that can be depended upon to remain applied with the pressure initially placed in the cylinder. After this the power will be figured on the basis of a 50

pound cylinder pressure and the 20% gain, the result of the higher pressure obtained in an emergency application will be a reserve force for use in case a stop in the shortest possible distance is desired.

Q.-G. S. L.—Why is it that the brakes do not seem to hold so well sometimes at the bottom of a long grade as they did part way down the grade?

warm

A.-A brake shoe is somewhat of a highspeed reducing valve in itself, that is the friction tends to fall as the heat becomes greater than a certain amount. The friction increases when the shoe becomes as compared to what is obtained with a very cold shoe. When a heavy train is started down a grade the holding power seems to increase for a time; this is due to the grease wearing off of the wheel tread, to the bearing becoming better and to the friction becoming greater. As the train proceeds and the shoes become gradually warmer until they are finally hot, the total amount of friction becomes less until it is finally necessary to make a heavier reduction to obtain a given amount of retarding power. As you state there are times on certain grades where the brakes do not hold as well at the foot of the grade as they did farther back. While this is true it would be difficult to state upon just what percentage of grade this result occurs as this would vary with the kind of brake shoe used, the weight of car and its carrying capacity, etc.

Boilers.

J. W. READING.

(Continued from January JOURNAL.) While such rapid progress is going on in mechanical work, it often proves of advantage to the seeker after knowledge to take a glance backward; in fact, he must do this to keep a clear idea of the progress that has been made.

It has been said that the "goal of today is the starting point of tomorrow." The steps by which the goal has been reached are of more than passing interest to the student of the past, as well as to the worker of today. The history of past experience gives encouragement to those who wish to enter new fields of invention.

The development of the steam boiler has depended almost entirely on the work of the boiler designer and maker. The early boilermakers were very much handicapped by the want of suitable material, only small plates being obtainable and angle iron unknown.

As improvements were made in the manufacture of boiler iron, the ratio of improvement was in evidence in the designing and manufacturing of a better grade of boilers.

When mild steel was first introduced the material for a time was considered of doubtful reliability, while now mild steel is almost exclusively used in the manufacture of the steam boiler. Mild steel, as made at the present time, seemingly, could not be bettered. It can be used for boilers of any shape or design. It can be welded and pressed into almost any desired shape. With material of such high perfection as can now be obtained and with the improved means for doing the work, the boilermakers of today can hardly realize how the early workers were hampered by the primitive tools and the want of suitable material.

Water tube boilers now so rapidly coming into favor, were, in the early days of their manufacture, very unsatisfactory owing to the difficulty of obtaining good iron or steel tubes. The first welded tubes were made for gas supply only, and proved to be quite unsuitable for steam pressure. Now the most perfect of tubes are made from both iron and steel, either welded or solid drawn.

I have been searching among my books and taking advantage of the public library to see what information could be obtained regarding the inception and progress made from time to time in the improvement of the steam boiler, and find that the first authentic record of power from steam was made by Hero of Alexandria, 150 B. C. Before Hero's time writers had only vaguely alluded to steam and its various properties. About Hero but little is definitely known. Mr. Bennett Woodcroft in his work translated from the orignal Greek, says that when Hero's name and place of abode have been

STEAM ENGINE AND BOILER, BY HERO OF
ALEXANDRIA.

given it is all that can be positively affirmed. It is shown in the writings of Hero that he knew of the expansion of air by heat and he showed that it might be made use of. He also knew of the formation of steam by heating water and gives two ways in which steam pressure so obtained can be used to produce motion. He shows that a light ball may be kept dancing on a jet of steam issuing from a small pipe and describes the apparatus as follows:

"Underneath a cauldron containing water and closed at the top a fire is lighted. From the covering a tube runs upward, at the extremity of which, communicating with it, is a hollow hemisphere. If we put a light ball into the hemisphere it will be found that the steam from the cauldron rising through the tube lifts the ball so that it is suspended."

Here we have the earliest boiler described as a "cauldron" containing water and closed at tha top.

In Hero's second description he shows how a rotary motion can be obtained by the reaction of a jet of steam. This is usually considered, and probably correctly so, as being the first steam engine. Hero's description of this engine is as follows:

"Place a cauldron over the fire; a ball shall revolve on a pivot. A fire is lighted

under a cauldron containing water and covered at the mouth by a lid. With this a bent tube communicates, the upper extremity of the tube being fitted into a hollow ball; on the opposite of the bent tube there is a support resting on lid which is pivoted into the ball. The ball contains two bent pipes communicating with it at the opposite extremities. As the cauldron gets hot it will be found that the steam entering the ball through the hollow pipe passes out through the bent pipes causing the ball to revolve."

Such was the first engine and boiler and for many years nothing different was made of which there is any record. This engine was nothing more than a toy to be brought up again and again at varying periods of time.

In the museum at Naples, amongst many interesting relics of the ancient city of Pompeii, are several small copper boilers, probably used only for heating water for cooking purposes. Two of these

SMALL BOILER FOUND AT POMPEII, NOW IN THE MUSEUM AT NAPLES.

SECTION OF SMALL BOILER FOUND IN POMPEII.

boilers are especially worthy of note, as having internal fireboxes and tubular fire bars connecting the water spaces on the opposite sides of the box. The fuel used in these boilers is supposed to have been charcoal, as pieces of this substance have been found with other heating vessels at Pompeii. The ornamentation of these ancient stoves, or boilers, is extremely elegant, which is a feature not found in modern boilers. The inside of both examples is quite ingenious and advanced, being built for fuel economy. It was many years after the destruction of Pompeii before boilers were constructed showing great ingenuity. Parties who have seen the boilers state that the workmanship is good; the material used is either sheet copper or bronze, the joints being brazed or soldered together.

It was about 17 centuries after Hero before any record was made of steam as a power. It is recorded that in A. D. 1543, Blasco de Garay, a sea captain of Spain, built a boat which was propelled by steam. Garay would never reveal the nature of his invention, but it was seen at the time of the trial that it consisted of a large cauldron of boiling water and some wheels of complicated movement on each side of the vessel. The story of the Spaniard's invention is rather vague, however, and cannot be vouched for as a fact.

In 1601 Giovanni Battista della Porta is said to have anticipated Sav ry and to have therefore used a boiler for raising steam. Nothing is positive as to the facts, however.

In 1615 Solomon de Caus, a French engineer and mathematician, published a work on the movement of forces, etc. He

illustrated a device consisting of a globular boiler placed over a fire, and simply let the steam blow the water out through a jet to make a fountain. An arrangement for filling the boiler is shown as a funnel and pipe fitted with a valve. It was nothing more than a toy and hardly came up to the one which Hero devised.

In 1663 the celebrated Marquis of Worcester left behind a most curious tract entitled, "A Century of Inventions," consisting of a hundred or more paragraphs, all more or less vague, but containing the germs of many inventions, some of which have since been developed. Paragraph 68 has given rise to many ingenious conjectures as to its meaning. By some it is stated to contain a somewhat indistinct foreshadowing of that which was brought out a few years afterwards by Savery and called "The Miner's Friend." Paragraph 68, as taken from "Gregory's Mechanics," reads as follows:

"68-An admirable and most forcible way to drive up water by fire, not by drawing it upwards, for that must be as the philosopher calleth it, which is but as such a distance. But this way hath no bounder, if the vessels be strong enough, for I have taken a piece of whole cannon, whereof the end was burst, and filled it three-quarters full of water, stopping and screwing up the broken end as also the touch hole, and making a constant fire burn under it. Within 24 hours it burst and made a great crack by the force within it. I have seen the water run like a constant fountain stream 40 feet high. One vessel of water rarefied by fire driveth up 40 of cold water, and a man that tends the work is but to turn two cocks. That one vessel of water being consumed, another begins to force and refill with cold water, and so successively; the fire tended and kept constant, which the self-same person may likewise abundantly perform in the interim between the necessity of turning the said cocks."

There is in the paragraph quoted a vague foreshadowing of Savery's engine, but neither Savery nor any other mortal could have made an engine from the de

scription given. It is stated that the Marquis did raise "water by fire" at his Castle of Raglan, but nothing definite is known about it.

Denys Papin about 1665 made his name celebrated by his invention of the wellknown 66 digester" which consisted principally of a boiler capable of withstanding a moderate pressure of steam and provided with a safety valve. He seems to have made many experiments with gunpowder as a means of obtaining

PAPIN'S ENGINE.