substance as hard as flint and almost impossible to remove, and it is for this reason that the greater part of this class are worthless for practical use, although some of them may show a very fine fire for a few hours.

Many processes have been patented for the manufacture of this gas, and there are two or three which are operated with more or less success. One of the latest in the New England field, although used for some years in other parts of the country, is the Archer Gas Fuel Process, which is in practical use in one of our mills. In this process there is a form of apparatus called a producer, which generates the gas, and it is in this producer that the dissociation of steam for the production of hydrogen gas, and the volatilization and decomposition of liquid hydrocarbons are effected. It is a step-by-step process. The oil is forced through a small pipe to the producer, where the gas is made. Here it is passed through copper coils surrounded by superheated steam. Thus the heated oil with its vapors unites through an injector with highly superheated steam, and together enters the horizontal S-shaped vaporizers, where the free carbon of the oil seizes upon and unites with the oxygen of the steam, leaving a considerable percentage of free hydrogen which passes into a central cast steel retort and the gas let out through its top and piped to the boiler.

Let us now pass on to a comparison of the merits and demerits of the different systems. The uncertainty or difference of opinion among scientific men as to the most important feature, namely, the combustion itself, makes such a comparison more difficult than it would be otherwise. Again, if every user of oil or even a majority of users were surely informed as to the efficiency of their especial apparatus, we could by comparison of figures reach the desired results, the only unknown quantities remaining being the cost and care of apparatus and life of the same.

Now the facts of the case are that but a very small percentage of oil users have any definite idea as to what results they are obtaining, and I surely think that there is quite a

large percentage who have never given this question any serious thought. This, of course, is especially apparent throughout the central States, where oil is cheap and handy, and therefore the fuel account is of less importance than in New England.

I think until recently the opinion has prevailed, to a greater or less extent, that if we could find some safe method of burning oil the problem of cheap fuel would be solved in one short and easy lesson. Taking advantage of this fact, inventors with more imaginative than inventive minds have placed upon the market, from time to time, various apparatus, whose principal recommendations lay in the promises of the promoters before a trial and its rapid death soon after trial. Still, these impractical inventions have all had a tendency to shake the confidence of steam users, thereby rendering the introduction of oil fuel difficult.

Another element of uncertainty, and to me a most important one, is in the oil itself. There is no doubt that many apparatus with some merit have been abandoned on account of unsatisfactory results of a test in which the quality of the oil used played a most important part, while no doubt poor apparatus have been greatly aided in the same way.

With an experience covering eight months of constant testing on a battery of three one hundred and seventy horsepower boilers, I find that there is at least a difference of twenty per cent. in the efficiency of the oil, all supposed to be the same grade of crude. I do not say that we get this variation at all times, but occasionally, with the conditions. exactly the same in the boiler room, you will find that you are by necessity consuming much more oil to obtain the usual results, while your fires show red, with more tendency to carbon. This trouble can no doubt be avoided to a great extent by the parties who ship the oil, and it would be well to bear this in mind when ordering.

To detect the objections to most forms of apparatus requires but a slight acquaintance with the subject, and a very limited knowledge of the principles of combustion.

No burner using oil in its natural state, or in bulk, we might say, can obtain as good results as when it is sprayed or gasified, simply from this fact, that it is impossible to introduce air sufficient for complete combustion at the right point. The simple introduction of air into the fire-box is not all that is needed. It must be introduced in such a way as to become thoroughly mixed with the flame during combustion. For this reason the first fires were very unsatisfactory, being smoky and red without much heat. Occasionally even now we hear of some one who is trying one of these types of oil fires, and I know of a mill which, within a few weeks after looking the ground over for the best thing, adopted for trial a modified form of pan fire, the pan being on the outside of the fire-box, and the oil allowed to drip inside, and, after enduring the odor of the warm oil for a week or two, discovered that the fuel account was growing visibly larger. Perhaps it is not strange that these gentlemen are now firm believers in "good old coal.”

Allowing that the oil must be sprayed or atomized, which is the most desirable to spray with, air or steam? Here is a question the answer to which in my opinion must be looked for as much in practice and practical work as in theory.

There is certainly nothing hidden or uncertain in the burning of oil sprayed with air. The oil in its finely divided condition burns freely while combustion is aided by the access of oxygen, but when steam is introduced the effect is different.

Chemistry teaches that steam is decomposed at a high temperature, and in the decomposition hydrogen is liberated. This temperature is without doubt attained at times in the fire-box. We must, therefore, decompose the steam and liberate hydrogen. Now when hydrogen enters into chemical union with oxygen more heat is developed than in the burning of the same weight of any other substance. Stopping at this point we find that we have decomposed the steam, liberated hydrogen, and by burning have increased greatly the temperature of our fire, therefore increasing its efficiency.

This is a correct theory which you will hear advanced by those interested in steam injectors, or steam as against air burners. This, of course, although good theory is worthless in practice, as it costs as much to liberate hydrogen as you get from its combustion. Is there then any advantage in the use of steam over air? The best I can do is to use the old adage, "The proof of the pudding is in the eating;" and there is not the slightest doubt in my mind but that the steam injectors as a class are doing more satisfactory work under boilers than the air injectors. With the air injectors we get a short, sharp flame with rapid and perfect combustion, and particularly adapted to small fires and light work; with the steam injectors the combustion is much slower, and for this reason we get a longer, heavier flame and one better adapted to large furnaces and boiler work.

Among the oil regions of the Caspian, and throughout all Russia, the steam injector in some form or other is the only one in use, at least to any extent, and the same statement is true of this country. Travel where you will among our oilburning communities and you will note the decided preference given to the steam burners, and the highest evaporation per pound of oil as far as I can learn has been reached with this same class.

With these observations it is natural and fair to suppose that there must be some practical advantage in the use of steam over air, whether by the decomposition of the steam or otherwise.

As you have probably discovered, the burner itself is the principal part of most of the apparatus adapted to use steam, and although they vary one from another in detail of construction or method of regulation, as a rule there is one simple principle displayed throughout them all, namely, the bringing together of the steam and oil through concentric pipes. I do not mean to make here any rash statements, but I do firmly believe that a burner can be made in your own shop which will answer the purpose as well as most of the burners in use, the expense of which will be the cost of two

short pieces of pipe, one common T and two three-quarter valves, with fifteen minutes' labor. I do not mean to say that this burner will be as attractive in appearance or as efficient as some, but the principle is there complete, without a royalty. We can scarcely read an item or opinion on oil as a fuel without finding some mention of the liability of trouble arising from the stopping up of the pipes or burners, and many there are to-day who are struggling with this difficulty; and the cause of the trouble is not always from the formation of coke or carbon, but from dirt, or foreign substances in the oil which are too large to pass through the necessarily small orifice in the burner. At times the scale which forms in the pipes breaks off and the flakes lodge in the burners. Of course the smaller the oil outlet and the dirtier the oil the more liable you are to trouble.

Another difficulty which is found with all steam burners is the necessary variation in the condition of the fire, due to the fluctuation of the steam pressure in the main. It is easily understood how, with the steam pressure at one hundred pounds, the velocity of the fire, and therefore the condition, varies greatly from steam at fifty pounds. This can be avoided by the use of a separate boiler, where the pressure can be easily controlled, or by the use of a pressure regulator, which I do not think would work well under such conditions.

It is possible to get a very unsatisfactory fire from the best of the steam injectors, and more care is necessary in the application to boilers than with the air injectors, on account of the liability of the condensation. of the steam against cold surfaces before combustion takes place.

In the Archer Gas Fuel Process the gas is manufactured as fast as required and passed to the fire-box in pipes, no burners being used or contraction of the pipe in any way, therefore doing away entirely with the trouble from stoppages. The fires are extinguished by shutting off the supply of oil, thereby doing away with any accumulation of gas, while the