It passes through very uniformly. When I was a boy, anthracite was just coming into use. We were obliged to buy it in the lump, and break it up with a hammer. It was hard to keep up a fire in those days. We don't have that trouble nowadays, for the coal is sized. We have what is called " range" coal, of a very good size to burn, for ordinary grates and stoves. If we want to keep a large fire, we want it in larger lumps, so that the ashes will not fill up the spaces between, nor prevent the access of the air. The great secret of burning coal to advantage, is to have it so that the air will pass pretty freely through. It is found by experiments, that have been made with some care, that we generally use, in burning coal of almost any sort, twice as much air as is absolutely necessary. To support the combustion of coal, it is necessary to use the oxygen of the air, and to bring it into contact with the coal. If we break up coal very small, we can bring the air in closer contact: or, theoretically, it would be better to have the coal in the form of pea coal; the spaces are smaller, the oxygen is brought in closer contact, and it is used up. If we admit more air than is necessary, this air carries off the heat, for the air must go off a good deal hotter than the steam in the boiler, if it is steam we are making. We introduce cold air, and heat it up to four or five hundred degrees. It will go off generally, in most manufactories, at about 500° Fahrenheit. Of course, if we introduce double the amount, or treble the amount, of air that is necessary, as is sometimes done, it carries off a great deal of heat. Theoretically, if we could bring the air into complete contact with the burning coal, we should not use so much coal. The heat produced would be more intense and available. But, practically, I am not at all astonished to see the results that have been obtained. The pea coal produces an ash that fills up the spaces between. The spaces are very small: when the ash is formed, it fills them up, and you cannot separate it so easily; consequently the air will force itself through in some spots, and not in others. If you could keep the coal clean all the time, it would be another thing. If you have coarser coal, there is much less trouble with its filling up the spaces so that the air cannot get through equally to every part of the fire. Egg coal is a good deal better on that account, for keeping a clean fire. We have particles of slate and particles of ash, and they do not fill up completely the

spaces between. The air can get through, and we can have a pretty complete combustion. The ash in the red-ash coal will fuse to a clinker. That is objectionable, because the clinker fills up the grate, and prevents the access of air. If we have a very intense fire, we are very apt to get clinker. I think every one who has looked at this matter will find that with pea coal you have a pretty intense combustion right through the grate, just where the ash is most abundant, and is in a good position to be fused by this intense heat produced: And it will be found by careful examination that the amount of clinker produced by pea coal will be much greater than that produced by egg coal, or even by what we commonly call "steam coal," or furnace coal, coal of a larger size. The heat is very intense in just that spot, perhaps one or two inches above the grate.

I will mention here the experiments made by Deville, in France. He wanted to get up an intense heat that would melt. platinum. He found he could do it with a blast furnace, with coke broken up to the size of peas. He found that where the blast was introduced into a furnace of this sort, the intensest heat was just about two inches high. If we take pea coal, and have the air introduced by its own force, or blown into the ashpit, the heat is intense where we should prefer not to have it intense. We should prefer to have it intense near the top of the coal. If you use small coal, and have the fire of any depth, it is absolutely necessary to blow into the ash-pit, and you have the condition that Deville had when blowing air into his furnace. The combustion is very perfect in the small space where it is taking place, and the heat is intense, and fuses the ashes together, and the grate becomes covered with a sheet of clinker. But no further combustion can take place until that clinker is broken up. It would be interesting if we could have experiments made with still larger sizes. But it would be necessary in all cases to state the depth of the coal on the grate, of course. If we use the pea coal, and want to keep a good fire and have combustion complete, we cannot have a high stratum; for if we fill the fireplace pretty full, the small spaces will produce too much friction. If we use egg coal, we can have it deeper. If we use coal still larger, we can have it deeper still. But, if we take the very largest coal there is, one difficulty is that the largest coal is apt, when thrown into the

fire, to snap all to pieces, and we get coal of all sizes. Really here is an objection again; because, if it snaps to pieces in different sized lumps, the small lumps would fill up these spaces where the air ought to go through. If we take the lump coal and break it up rudely and throw it into the fire, we cannot expect to have the fire very deep, and have it burn to good advantage. You can probably have the deepest fire with coal of the egg size; that having been broken quite uniformly, it is not so liable to splinter when thrown into the fire. This splintering is occasioned by the gas retained by the anthracite coal. Anthracite coal has been found by late experiments to retain a large quantity of gas, a quantity which is equal to twenty times its own bulk,- by the peculiar force of attraction. Of course this is retained by the peculiar substance of the coal, and when coal is thrown into the fire the gas tends to escape, and the coal is blown to pieces. This will happen to a large extent with small coal as well as with large; but the smaller the coal is broken, the less in proportion there is of this splintering, and the less, therefore, there is of inequality produced in the size of the particles which are in the fire. If you have large lumps and small lumps in between them, you can fill up the spaces as completely as if the fire had been burning all the time, and it was filled with ashes. It is a great disadvantage to keep stirring the fire, for we shall let through the grate more or less of the small coal. That is a necessity, and you can't help it; and this small coal that passes through into the ash-pit is lost,-four or five per cent of all the coal used, in some cases. It amounts to a good deal more than the smoke which we get from bituminous coal. That looks large, but amounts to very little really. The anthracite coal, as we all know, is particularly advantageous for tubular boilers, because it does not make the smoke and soot which is liable to fill up the tubes. We can have tubes of two and a half to three inches diameter, and not have to clean them out very often. But on the other hand, the anthracite does make more ash than the bituminous. This ash is very light, and is carried forward into the tubes, so as to fill them up; and they must gradually be filled up. That is not so bad as the flakes of soot which accumulate in the tubes. The bituminous coal wants to be burned with pretty large flues; but undoubtedly the bituminous coal can be burned under boilers, provided we have three-inch tubes: the Cumberland coal is very good in that respect; it can never yield so

much refuse as anthracite, and the price per ton is about the same. If we take bituminous coal, or Province coal, we shall find, as a general thing, a pretty large amount of ash, and unfortunately that ash is very fusible. I have been astonished, in burning Pictou coal on a large scale, to see how soon the grate would be covered with a complete sheet of clinker. This is always the case where you want a pretty hot fire. You must run in your bars, break it up, and open the door and hook it out, and there is a great deal of heat lost in that process. A rule of prime importance in all cases where we have a fire is to keep the fire-door open just as little as possible: you find that firemen do not think very much often of this point. I have seen one keep his fire-door open, turn around and talk, and spend five minutes in that way. He ought to throw in the coal, and get all through with it in half a minute; then there would be very little trouble: the trouble is, that, if the grate-door is open, say, sixteen by twelve inches, the cold air is rushing in with prodigious velocity, carrying off the heat, mixing a great quantity of cold air with the hot air, and carrying it off up chimney. There is a great deal to be saved, I think, by getting men who understand the business of firing; we don't always exercise care enough about that. You will find all the difference in the world about that. Some men are naturally pretty slow in their motions, and it will take them two or three times as long to fire up, as it will other men. If a grate is to be cleaned out, it takes them two or three times as long as it does other men. I have seen this particularly in the smelting of lead, where I have had occasion to use a reverberatory furnace. I had two men, one working at night, and the other in the daytime; one man would always get out from the same charges and the same amount of firing one hundred and fifty pounds more of lead than the other. I paid those men the same price, but I got sick of it after a while. It is not worth while to pay one man a dollar and a half per day for wasting one hundred and fifty pounds of lead worth five cents per pound. People do not always think of this. I believe you will find it more advantageous to pay a man five or six dollars per day, than two: a better class of men, who will be intelligent enough to see to all these little points. It makes a difference whether you have your fire-door open five minutes or two; and it makes a great deal of difference whether you hook the coal unnecessarily, and let it through the grate. A great deal of this latter difficulty of letting coal

through the grate, has been attempted to be obviated by patent grates. We have all sorts of patent grates, some of them shaking grates, very good; others, grates with very small spaces, which, therefore, can be coated over with clinkers pretty easily, and soon are stopped up. The manufacturers will always warrant that they will save you thirty per cent at least of the fuel used before; I cannot say that this is exactly so. There is an advantage in the shaking grate, because you can clear out the ashes without opening the fire-door. Of course, if you can keep the grate clean, and break up the clinkers without opening the fire-door, it is a great deal better. I had occasion to look into this matter of grates a few years ago. A man came along with a particular grate-bar, supposed to save thirty per cent of the coal. He had certificates from manufacturers to show that it would do it, and was quite sure that that was the case. I told him I would take one set, and we would try those. The old grates were very heavy, -one hundred and twenty pounds per piece, and they had never been bent or got out of shape at all; they worked very well. We put in this set. When they came, I told our man to observe very carefully the amount of ashes he got through, and weigh it all, and the amount of ashes from the other fires. He did not find any difference at all in the amount of coal consumed, or in the amount of ashes; but in six months the new grate was used up pretty nearly,warped all out of shape. I took it out, and put in the old grate-bars, taken out of that same fire, and they lasted four or five years without any change. One of the advantages claimed for the new grate was, that it would never warp or get out of shape: it was said to be a great deal better than any of the old grates. I met this same man who introduced this grate a year afterwards in Providence, and asked him about his grate-bar. He said, "I have taken up another one now. That bar was not quite as good as the one I am introducing now. This new one is a great improvement on the old." I told him I didn't believe there was a great deal of improvement about the matter any way. I told him my experience with the grate-bar I had introduced in place of my old one. There is more in the fireman than there is in the grate-bar, and more in man than there is in the coal.

As to the question of the weathering of coal, of course it is important to keep coal covered on one account. It is disadvantageous to have coal out of doors in rainy weather or snowy