was specially designed for oil fuel and high rates of forcing, while the one tested in 1910 was designed primarily for coal as fuel. The difference is mainly in the much larger amount of furnace volume in the "Oklahoma's" boilers. On this test, the unprecedented rate of 1.23 pounds of oil and 18.7 pounds of water from and at 212° per square foot of heating surface was obtained.

The importance of adequate furnace volume is very great, and this is one of the features in which the Babcock & Wilcox boiler is superior to all others. Indeed this boiler is specially adapted to the use of liquid fuel, and a comparison of its performance with those of other boilers shows a higher efficiency (at least ten per cent.) and a higher capacity.

ADVANTAGES OF LIQUID FUEL

Among the advantages of liquid fuel for marine boilers may be mentioned:

Greater convenience and uniformity of operation.

Greatly increased cleanliness.

Increased bunker capacity due to greater thermal value.

Ability to utilize double-bottom and other spaces not available for coal.

Greatly reduced fire room force.

Ease and rapidity of taking fuel on board.

Higher efficiency of boiler due to uniform conditions of working, absence of opening doors for firing, and no loss from ashes and unburnt fuel.

Absence of the nuisance of ashes and cleaning fires.

Elimination of "stand-by" losses.

The following table gives the specific gravity and weight of oil corresponding to readings on Baumé scale:

The two following tables are given to show equivalent values of coal and of oil in heat effect and at varying prices. In comparing the heat effect, allowance has been made for the greater efficiency of the boiler when using

BABCOCK & WILCOX BOILER, U. S. NAVAL OIL-FUEL TESTING-PLANT, NAVY YARD, PHILADELPHIA, PA. THIS BOILER HOLDS THE WORLD'S RECORD FOR ECONOMY AND CAPACITY, HAVING EVAPORATED 18.7 LBS. OF WATER PER SQ. FT. OF HEATING SURFACE PER HOUR AND 15.3 LBS. OF WATER PER LB. OF OIL (BOTH F. AND A. 212° F.) WHEN BURNING 1.23 LBS. OF OIL PER SQ. FT. OF HEATING SURFACE PER HOUR. THE BOILER HAS 4000 SQ. FT. OF H. S., AND IS A DUPLICATE OF TWELVE FOR U. S. S. "OKLAHOMA."

oil. Tests on the same boiler at the Babcock & Wilcox works showed that the efficiency with oil is ten per cent. (of the coal efficiency) greater than with coal. The thermal value of the oil has been taken at 19,000 B. T. U., which is an average value for Texas crude. In the second table, comparing costs, coal of 14,000 B. T. U. (Cumberland or George's Creek) has been used. The density of the oil has been taken at .932 specific gravity (20.7 Baumé), which makes the weight of a barrel of 41 gallons, 314 pounds. A ton of coal is taken as 2240 pounds.

The chemical composition and the calorific value of oils vary even with samples from the same general locality, so that, in accurate work, it The following table gives Mexican oils.

is always necessary to have an analysis made. data of some analyses of Texas, California, and

CALORIFIC VALUE, SPECIFIC GRAVITY, ETC., OF FUEL OILS

The burner used by The Babcock & Wilcox Company is the invention of Mr. E. H. Peabody. He thus describes it in a paper read before The Society of Naval Architects and Marine Engineers, November, 1912:

"In the light of our experiments begun in 1907 we have come to believe that the best rotative effect on the oil is produced by the tangential delivery method, and it seems plain that the best way to reduce friction is to reduce the amount of surface to which the oil is exposed in its travel through the burner after it begins to whirl and until its exit from the tip. We have also come to attach great importance to simplicity in everything connected with oil burning and believe that the oil burner itself should be of simple construction, easily taken apart, and so designed that when taken apart all the small passages and wearing surfaces will be exposed for inspection, cleaning, and repair.

"The results of the writer's efforts to construct a burner to meet these requirements are shown in the cut on p. 69. Oil is delivered under pressure to an annular channel cut into the face of a nozzle upon which is screwed a tip having a very small central chamber communicating with a discharge orifice. Between the nozzle and the tip a thin washer or disc is inserted and held firmly in place. This has a hole in the center corresponding with the diameter of the central chamber of the tip, and small slots or ducts, extending tangentially from the edges of the central opening outward toward the periphery of the washer, long enough to overlap the annular channel of the nozzle and put it in communication with the central chamber. The effect is that, when the burner is assembled with the washer in place, oil is delivered through the ducts tangentially to the central chamber where it rapidly revolves and almost immediately is discharged through the orifice in the tip.

"In order to correct a popular fallacy I beg to call attention here to the fact that no mechanical atomizer produces a revolving spray, but the particles of oil fly off in straight lines under the influence of centrifugal force, thus forming

a hollow, conical spray. The fineness of this spray, i. e., the minuteness of the particles forming it, has a most important bearing on the results obtained in the furnace. It is possible with some forms of steam atomizers to atomize oil so finely that no flame at all will be produced, the incandescent combustion chamber being filled with a clear invisible gas and every brick being discernible. I doubt if this condition of flameless combustion can be produced with mechanical atomizers and heavy oil, nor is it desirable under any circumstances for the simple reason that it costs too much.

"With the production of flame, however, furnace design assumes an added importance, for the flame must be distributed evenly and without localizing on the heating surface of the boiler, and the gases must be given time and space in which to expand and burn as nearly as possible to completion before being cooled and the flame extinguished by contact with the tubes of the boiler. These points become exceedingly vital when the boiler is forced to the requirements now demanded in naval service."

AIR REGISTER OR IMPELLER

This device for regulating and directing the admission of air, and referred to on page 63, is the invention of Messrs. Peabody and Irish, and reference is made to it in the paper of Mr. Peabody, just quoted, as follows:

"Great delicacy is required in introducing the air for combustion, very slight changes affecting the results in unsuspected ways, and while almost any method may result in smokeless combustion, maximum economy and capacity can be secured only by careful and intelligent design.

"It is not necessary to give the air a whirling motion but, judging from our rather exhaustive experiments, better gas analyses are secured, lower air pressures are required, and less refinement of adjustment is needed if the air is brought into contact with the oil spray with the right sort of a twist. We have found the impeller plate, illustrated on this page, most effective in accomplishing this mixture, and our most satisfactory results have been obtained with it."