stack. If the deflector plate is placed too close to the tubes at the top it is liable to choke them so that they are of very little use to the engine, as it does not permit of an easy passage for the gases and smoke after leaving the tubes, practically choking them back. It is the usual habit of enginemen when booking work to be done, if they have had bad results for want of steam, to report "engine not steaming." This may appear to them to fill the bill, and they may even assume that it also relieves them of future responsibility in the case of a failure for steam.

If firemen would make a study of the smokebox apparatus they would in a great many cases understand by the way their fire was burning or not burning what was the probable cause, and could so advise the engineer as to their opinion, as he has not the same opportunity for observing the condition of the fire that the fireman has. If the engineer was able to say on his report "engine does not burn fire on the back section" or that "the left right-hand corner, etc., will not burn," how much easier it would be for the shop foreman to determine the cause and attend to the same at once. Where an engine is reported as not steaming it means that the front end has to be opened up, and if nothing appears to have moved out of place the engine is probably sent out again in the same shape. There is usually a certain amount of tardiness on the part of the shop staff officials in admitting that such and such work was done. It is very often the case of saying that nothing was wrong, and consequently did not need fixing. This has the effect of destroying the confidence of a good many young engineers as to their ability to determine the cause of bad steaming engines, with the result of them getting into the usual rut of "engine not steaming."

The Superheater.

The superheater is of necessity coming to the front with rapid strides, chiefly owing to the urgent needs and calls from every quarter for fuel economy. Superheating is not a newfangled idea, as some persons suppose, the opinion of some being that the superheater on a locomotive is something that has been imagined in the mind of some enthusiast on fuel economy, and is consequently additional apparatus with which to fill up the already crowded front end of a locomotive,

and which will result in nothing. As said before, superheating is not by any means a new idea, though at present it is being put to uses that were unheard of years ago.

Ever since the laws of expansion and contraction have become recognized, superheating, both of solids and gases, has been practiced with a definite purpose in view, viz., to gain a greater efficiency out of the substance being heated than could have been obtained by any other means.

There are two or three known laws that govern the working of the superheater on a steam engine. From one of these, called Mariotte's law, it is found that the density of a gas increases as the pressure increases, and decreases as the volume increases. From another, known as Gay-Lussac's law, we learn that if the pressure remains constant every increase of temperature of one degree F. produces in a given quantity of gas an expansion of 1/492 of its volume at 32 degrees F.

Now the principle of this should be very easy for a fireman to understand, in that every degree of superheat produces an expansion of the steam, which results either in greater pressure, if the volume is constant, or in greater volume if the pressure remains constant. The steam generated in a locomotive boiler is called saturated steam, and in fact steam in any boiler is in the same condition, saturated; that is to say, it has a certain amount of moisture with the steam. This is due to the bubbles of steam coming up through the water being surrounded by a thin film of water, and this thin film naturally causes an amount of water to become mixed with the steam; thus it is called saturated steam.

Superheated steam can be had in such a state of superheat as to evaporate all the moisture and produce a perfectly dry steam, or, as it is called, a steam gas. Up to this point the only efficiency that is gained by the superheater is in the perfect drying of the steam and increasing the heat content, but any heat applied above this increases the efficiency in another direction, viz., by expansion of the steam gas. This is easy to calculate, the amount of expansion of the steam being always the same providing the temperature of superheat is the same, as steam then comes within the same law as permanent gases, or Gay-Lussac's law.

As these formulas or calculations are usually figured from absolute tempera

tures and absolute pressures, it will be quite necessary for the reader to know at this time what is meant by absolute pressures and temperatures.

Absolute Pressure.-It is perhaps not necessary to explain to the ordinary fireman that the earth is surrounded by a gaseous mixture about fifty miles thick, called atmospheric air, which, except for a few minor gases, is composed chiefly of nitrogen and oxygen, the amount of oxygen being about 21 per cent. by volume and 23 per cent. by weight, the other 80 per cent. being nitrogen. Now this enormous thickness of air exerts a pressure upon the earth, and it is found to be equal to about 14.7 pounds to the square inch at sea level. This may not be easy to understand. Supposing a piece of board measuring four square feet were lying down and a man attempted to pick it up. There being a pressure of 14.7 pounds on each square inch and its area being 576 square inches, it would have a pressure of 8,467 pounds upon it, and he would be unable to lift it were it not for the fact that there is an equal pressure of air beneath it which overcomes the downward pressure.

If we take a piece of iron or steel of the same size as the receiver of an air pump, grind it to a perfect level, and have the receiver of the air pump ground to match it, making sure that it will be an air-tight fit when the piece of metal is placed over the receiver opening, and then pump all the air out of the receiver, we find that we are unable to lift it off. We say that it is held there by suction, but it is not; it is held there by atmospheric pressure.

We may take a tumbler and fill it with water, place a piece of thin cardboard perfectly air-tight upon the top, then turn it bottom upwards on our hand, lift it by the other hand from that one, and the cardboard will keep the water from running out, even though the tumbler is bottom up. If a pinhole were inserted in the bottom of the glass, which is now on top, the water would immediately run out, the reason for this being that before the hole was made the pressure of the atmosphere of 14.7 pounds per square inch was holding up the cardboard against the weight of the water, but as soon as the pinhole was made the same pressure was exerted above the water as that below it, and there was then nothing to support it, and water being heavier than

air it would naturally fall out. Now absolute pressure is figured from the condition of an empty space, or a vacuum, that has no pressure upon it. A pressure gauge on a locomotive shows, say, 160, 180 or 200 pounds per square inch; that is steam pressure above atmospheric pressure, so when making calculations which take into consideration the absolute pressure it will be necessary to add 14.7 pounds to any of the above gauge figures thus, 174.7, 194.7, 214.7.

So.

Absolute Temperature.-We naturally think that zero F. would be absolute temperature for our purpose, but it is not Absolute temperature is the temperature at which all vibrations of bodies, gaseous or other, cease. Everyone knows that a tuning fork, if struck, vibrates and gives off a musical note owing to the number of vibrations per second. Now at an extremely low temperature we could not get this note because the vibrations would cease, and it has been found by calculation that at about 460 degrees F. below zero F. all these vibrations cease. This is called absolute zero. To find the absolute temperature we add 460 degrees to the known temperature. Say steam at 200 pounds pressure has a temperature of 387.5 degrees F. The absolute temperature of steam at 200 pounds pressure then would be 387.5+460=847.5 degrees = absolute temperature.

We now understand what is meant by absolute temperature and absolute pres

sure.

Returning now to the subject of superheated steam, it is found that the steam in the locomotive which is heated on its way from the boiler to the cylinder is made more efficient not by extra pressure nor scarcely by extra volume (because the flow is continuous while engine is working), but by the temperature to which it is heated. It is calculated that if steam is heated 100 degrees F. above the temperature at which it issues from the boiler the resulting temperature is sufficient to thoroughly dry the steam. This of course makes it more efficient, and if heated again another 100 degrees it will prevent condensation due to the work it performs. Now it is calculated that with an engine carrying 160 to 200 pounds of steam pressure 20 to 30 per cent. of the power is actually unobtainable, due to condensation of the steam. without saying, then, that if an engine is provided with a good system of super

It goes

heating much more power ought to and will be obtained with the same gauge pressure. An engine carrying 160 pounds of steam with a good superheater will be nearly as efficient as an engine carrying 200 pounds without one.

As was noted when treating on the "Mechanical Equivalent of Heat," every degree of heat represents so much power, and though it is not practical to measure the exact amount of additional power due to a superheater on a locomotive it is easy to see the great advantage to be gained from its use, especially when we consider that this extra power is derived without any additional expense for fuel or for labor on the part of the fireman or engineer, giving as it does more efficient work at the same cost of labor and fuel, or, in other words, the same amount of work-with less labor and less cost of fuel-as could be had with steam of higher pressure not superheated, which is another point in favor of fuel economy on a railroad.

The superheater on a stationary boiler has an advantage over the locomotive superheater in that the results are greater and the trouble less. In the construction of a locomotive superheater arrangements have to be made whereby the hot gases can be prevented from overheating the superheater apparatus while the steam is shut off, such as when running down a grade or into a station, owing to the start ing valve being located between the boiler and the superheater, or the pipes and tubes would be burned out. In the case of a stationary boiler the starting valve is located beyond the superheater, and consequently when the steam is shut off from the engine the superheater can still be doing good work by reheating the steam, sometimes passing it up again through a long steam pipe that is in the center of the boiler, thereby adding heat to that of the water in the boiler. see that there is no need of shutting off the heat to this kind of superheater, as the flow of steam is continuous. Some day perhaps an inventor will come along with a new arrangement whereby the main operating valve of a locomotive will be placed beyond the superheater, between it and the steam chests, so that the superheater can be continuous in its action, and thereby produce greater efficiency than it does at present. There are a great many superheaters in use at the present time, and one of the best no doubt

We

is that in service on the Canadian Pacific Railway of Canada, called the "VaughanHorsey superheater." This is very efficient and is one of the easiest to do repairs to.

If any of the small superheater pipes give out it is only a small job to uncouple that set and replace it with a new one, owing to the couplings on the headers being very easy to get at. This is one of the most important attainments of the superheater inventor, i. e., to build it in such a way that repairs can be made at any roundhouse by the local staff in a few hours instead of having to hold an engine off its run for perhaps two or three days. The one in question receives well merited praise from shop and locomotive foremen on account of this important feature. There are several reasons why a superheater may not do good work, and failures have been due to things that will sometimes happen. Should the superheater tubes become blocked the apparatus is practically of no use until it is cleared. There is very little chance for the hot gases to pass through these tubes if choked, in which case the superheater pipes through which the steam flows would be receiving very little additional heat. If a fireman notices that his fire does not burn so well on the back section of the grates as formerly it would be well for him to acquaint the engineer of the fact, as the cause may be "choked tubes."

What has been said of firing on the back section of the grates, and the economical results obtained due to this, applies with greater force in connection with a superheater. In the first place, most of the hot gases pass through the upper tubes if the engine is drafted that way, and as their temperature is very high they are then making the superheater doubly effective by bringing such an intense heat to it. If most of the firing is done on the front section of the grates a lesser amount of hot gases will be going through these upper tubes, and of course that much effective heat will be taken away from the superheater tubes. Again, by keeping such an intense and constant heat going through these tubes and up at the tube sheet it is to a certain extent a

prevention against these large tubes leaking, which, should this occur, usually disables the engine until they are fixed.

As it is not intended that this should be a mechanical work we will not pursue this subject further.

Approaching a Grade.

It has often been asked how a man would prepare his fire for taking a grade. His own practical experience should tell him that if he has a full glass of water and a full head of steam he will have that much energy stored up to assist him in his heavy work up the grade. As to the depth of the fire, this can only be governed by the class of coal in use, but in the majority of cases it will be found of great advantage to put in a few extra scoops full on approaching a grade of any length. The light exhaust of the engine while running on the level stretch of track before reaching a grade will usually burn off some of the gases or volatile matter, though there may be a certain amount of loss due to unconsumed gases going out of the stack as smoke. However, this is more than made up for afterwards in the greater efficiency of the body of the fire, which, owing to the extra amount of coal put in, does not need replenishing so often, the largest amount of heat units being derived from the body of the fire and the extra heavy exhaust at the time of going up the grade being just what is needed for complete combustion. Again, there is another advantage to the fireman in this method of approaching a grade. He does not have to open the firebox door so often while the engine is working hard, and this is a means of assisting in keeping the tubes and sheets from leaking. Everyone knows how detrimental it is to an engine to have its firebox door opened too often while the engine is working hard. I am offering this more as a suggestion, giving the possible advantages to be gained by this means, and have offered the same suggestion to a few heads of locomotive departments, and they were agreed as to its advantage. I am sure that it will be worth the while

of any fireman to take it into consideration, giving it a trial whenever possible. His practical knowledge and experience with the engine he is firing, combined with this suggestion, ought to be productive of good results. Speaking of the bad effect of opening the fire door too often, I do not wish to give the impression that it is the right thing to do to make a practice of opening the door only once in a while and then putting in a heavy fire. I once saw a fireman put in twenty-one scoops of coal in two fires, just before arriving at a station, on a passenger train, and directly the signal was given and the engineer opened the throttle the door was opened and thirteen scoopfuls were piled in at one firing, with the result that while going up the three-mile grade volumes of smoke rolled out of the stack all the way. However, as the coal was one which would be called by enginemen quick steaming coal, he got plenty of steam. If it had been some classes of coal the engine would have stalled under such treatment. As it was, a great amount of heating power was lost and the company who purchased this coal were the losers, while of course it was considerably more work for the fireman to put in this amount of coal than if he had put in two-thirds of it, which would have been plenty. If this had been coal with a heavy body, having plenty of tarry matter, it is more than probable that they would not have made the grade. This heavy charging would have resulted in cooling off a large part of the firebox area and lowering the temperature of the gases, so that the tarry matter would start clinging to the netting, and even if it did not choke it completely it would have so affected the draft that not enough air could have got through for the complete combustion of either the gases or the coke.

Extra Trains.

The Standard Code of Train Rules defines an extra train as being a train not authorized by time-table schedule. Rule 97 puts the authority for the running of

an extra train in the hands of one person, the train dispatcher, so that proper protection may be arranged between opposing extra trains when necessary. But it will be noticed that there is no superior

ity between extra trains unless it is made by train order, with the exception that at meeting points between extra trains the train in the inferior time-table direction must take the siding. A careful study of the rules will show that one extra cannot be made superior to another under a Form C order by authority of such form, although as a matter of fact orders are issued on nearly all roads giving one extra right over another extra, but without the authority or the restraining guidance of specific rules properly explained. The Train Rules Committee who framed the Standard Code refused to insert an example under Form C which could be used between extra trains, claiming that as extra trains had no schedule such practice would virtually fix a meeting point in any case. For example, if engine 546 is given an order to run extra from A to B with right over extra 234, which is moving from Z to A, it would hold extra 234 at B for extra 546, and the committee seemed to think that a meeting order would be better than a right of track. But it ofttimes happens that one extra train is of such importance that it is not desirable to fix a meeting point for it with an opposing extra for fear that it may be unnecessarily delayed, and it is in such cases that a right of track order supplemented by a wait order is desirable if not necessary. The third example of Form G furnishes an example which can be used in some cases to advantage, but owing to its length few dispatchers have time to use the order, and for this reason it is my opinion that an example should be added to Form C as follows: "Extra 546 has right over extra 234 A to H and waits at F until 9 a. m. and G until 9:30 a. m. for extra 234." This should be followed by an explanation stating that the first named train has right over the second named train between the points designated, but must not pass the intermediate designated points before the time specified unless the second named train has arrived, with a further explanation that the second named train must be clear of the main track by the specified time at the designated point or before reaching it. In issuing a right of track order between extra trains there is danger unless the right of track is given to the end of the run of the first named train, or to the end of single track, or to a

point already reached and at which the order is received by the second named train. In starting an extra train from a point at which it is to meet an opposing extra train the order should read, "After extra 234 arrives at A engine 546 will run extra A to B."

Form G is for running extra trains, and there are three examples given. The first example directs an engine to run extra from one designated point to another, and under this example an extra need not protect against opposing extra trains unless it is directed by train order to do so. The second example is for running an engine extra from one point to another and return to a certain point; under such an order the extra must go to the second point named in the order before it is permitted to return. That is, the order must be fulfilled in the way in which it is given. If for any reason the extra has to return to the third point named in the order before it reaches the second point, it must have another order to run extra. The third example

is generally used for passenger trains and is so arranged as to make a schedule for the extra train. Ofttimes such an order gives the extra right over all trains, and in some cases trainmen have been known to run through yard limits at the same rate of speed as though it was a firstclass train instead of an extra. It must be remembered that an extra, moving under such an order, is still an extra, and, while it has right over all trains, it must be governed by the rules directing the movements of an extra while it is passing through yard limits.

In the case where an extra train ties up on the road for a certain length of time and then reports for orders, the Standard Rules do not provide any form for giving this extra train information as to what trains, which are overdue, have arrived or left that station. If the extra happens to be tied up at a register station this information can be obtained from the train register, but if it is not it becomes of great importance that it receive dependable information as to what schedules have been fulfilled. To cover such cases as this an order should be isused to the extra reading as follows: "All trains due at H at 6 a. m. have arrived or left except No. 3 and No. 4." Such an order is necessary in order to conform with Rule 83, which states that