The laboratory was in charge of J. D. Davis, chemist, who reported to the chief chemist at Pittsburgh. Mr. Davis was aided by H. M. Cooper, assistant chemist, and E. L. Wallace, J. G. Fairchild, J. P. Bader, G. Bornscheuer, W. A. Gonzales, and I. M. Bortman, junior chemists. and A. Christie and A. Engel, analysts.

BOILER AND FURNACE EFFICIENCY.

When the Government began the systematic testing of coal at the fuel-testing plant in St. Louis in 1904 the factors controlling the efficient utilization of coal in steam-boiler plants were given especial attention and have since been part of its fuel-testing investigations.

At the close of the fiscal year 1914 unfinished work included tests at Pittsburgh of two types of heating boilers for the Treasury Department and the preparation of a report on saving fuel in heating a house. During the fiscal year 1915 the boiler tests were continued, and recently a new boiler of different design has been substituted for one of those tested. A report on heating a house is in process of publication.

At the request of the War Department, tests of a large number of American coals and of coke, oil, and wood in several types of small residence-heating boilers are to be made. The results will be of great value to the public.

During the year tests have been conducted in connection with the award of contracts for coal at the workhouse for the District of Columbia and at the Carlisle Indian School.

At the request of the Public Printer, acceptance tests of new boiler and stoker equipment for the Government Printing Office power plant were made, and later clinker troubles at that plant were studied. Similar troubles at the power plant in the General Land Office building in Washington were also investigated and were corrected through cooperation with the fuel-inspection section of the bureau.

A representative of the bureau assisted in a test of Matanuska (Alaska) coal on board the armored cruiser Maryland. In nearly every way this coal compared favorably with the eastern coal regularly used by the Navy.

Comparative tests were run to ascertain the effect of using a socalled coal-saving powder. Claims of the increased fuel value of coal treated with this powder were not substantiated.

Plans were developed for testing during the coming year various devices for observing or recording the density of smoke.

Conditions in the power plant of the New York Navy Yard were studied, and ways of increasing the output of the power plant and decreasing the amount of smoke were recomended.

The investigations of boiler and furnace efficiency were under the direction of S. B. Flagg, engineer, aided by G. C. Cook, assistant fuel engineer, and R. L. Beers, junior fuel engineer.

FUEL-EFFICIENCY LABORATORY.

The fuel-efficiency laboratory at the Pittsburgh experiment station is making small-scale experiments to ascertain the relative importance of different features of boiler and furnace construction on the capacity and efficiency of steam power plants and the economic utili

zation of fuels under steam boilers. The work during the year consisted mainly of two groups of investigations, as follows: (a) The study of the combustion of coal, with the aim of determining proper designs of furnaces for burning each kind of fuel and the most efficient method of firing it; (b) the study of the transmission of heat from the hot products of combustion into the boiler water, in order to obtain accurate data for designing efficient boilers.

THE COMBUSTION OF COAL.

Combustion of solid fuels takes place partly on the grate and partly in the space above and beyond the fuel bed. In the fuel bed the fixed carbon of the fuel is partly burned, and the volatile matter is distilled from the freshly fired coal. In the combustion space above and beyond the fuel bed the volatile matter is burned and also the partly burned fixed carbon that rises from the fuel bed in the form of carbon monoxide.

About 50 tests were made in a hand-fired furnace specially designed for studying combustion, samples of gas being taken and temperatures measured at various heights from the grate. Three kinds of fuels were used-Pittsburgh coal, anthracite coal, and coke.

These tests show definitely that no matter how much air is forced through the fuel bed all the free oxygen is used in the first 3 to 4 inches above the grate. Beyond this height the products of combustion are largely combustible gases, so that if a fuel bed is 4 to 6 inches thick and level the gases rising from it constitute fairly good producer gas. This is true with all ordinary rates of combustion, with 20 to 180 pounds of fuel per square foot of grate per hour, and with all three fuels. Hence, enough air for complete combustion can not be supplied through such a fuel bed more than 4 inches thick, even with forced-draft apparatus, and air must be added over the fuel bed to insure complete combustion and to eliminate smoke.

As regards clinker formation, these tests showed that the ash fuses in the reducing layer of the fuel bed and solidifies and forms a sheet of clinkers as it sinks toward the grate. A series of tests has been started to ascertain the relation between the fusing temperature of ash as determined in the chemical laboratory and the formation of clinker in boiler furnaces.

A report on the process of combustion in the fuel bed is about completed.

In the study of combustion in the space beyond the fuel bed one series of tests with a furnace having a long combustion chamber and a Murphy stoker has been completed. The stoker is being replaced with a hand-fired furnace, and another series of tests is planned with the modified apparatus.

An important conclusion from the investigations made is that with a Murphy stoker efficient combustion of high-volatile coals can not be obtained with a combustion space shorter than 10 feet-a combustion space larger than that used in many commercial plantsso that in those plants efficient combustion is clearly impossible.

HEAT TRANSMISSION INTO STEAM BOILERS.

To investigate the transmission of heat into steam boilers a tubular boiler 20 feet long and a furnace for burning natural gas were used. In future tests the size and length of the tubes of the boiler will be

varied. The tests with this apparatus are well under way, and the results are consistent, accurate methods of temperature measurement at all points of the heat transfer having been developed. The data obtained from these investigations will help to place boiler designing on a rational basis; also hazy ideas on the effect of scale on boiler efficiency will be cleared up.

A report on heat transmission through boiler tubes, by Henry Kreisinger and J. F. Barkley, was completed and is in course of publication by the bureau.

The work of the fuel-efficiency laboratory was in charge of Henry Kreisinger, engineer, assisted by C. E. Augustine, assistant engineer, J. F. Barkley, junior electrical engineer, and E. M. Muncey, physical laboratory aid.

GAS-PRODUCER INVESTIGATIONS.

Investigations of the value of different coals as gas-producer fuel and the study of the factors governing the combustion of fuels in gas producers were begun by the Government at the fuel-testing plant at St. Louis, Mo., in 1904, and were continued at Norfolk, Va., and Pittsburgh, Pa.

Early in the fiscal year 1915 an experimental U-tube gas producer of the slagging type was completed, but owing to a lack of funds tests were suspended in September, 1914, before enough tests could be made to show the operating characteristics of the new design. However, in all of the tests made the slagging of the ash was very unsatisfactory.

The results of the bureau's investigation of the slagging type of producer proved a disappointment, because positive results were not obtained. It is believed, however, that the results obtained are not conclusive and that further study and experiment might give more favorable results. The results of the work done prior to discontinuing the gas-producer investigations have been largely negative, but the following general conclusions may be drawn:

1. With good metallurgical coke and an ample supply of blastfurnace slag for flux, a gas producer of the blast-furnace type may operate continuously and yield good gas and satisfactory slag.

2. With any fuel other than good coke the slag chills and collects in the slag pot, necessitating a shut-down.

3. There is little prospect of bony coals or other high-ash fuels being utilized in slagging producers.

4. With a slagging producer, the problem is not to make satisfactory gas, for the gas is invariably of good quality, but to produce a slag that will not solidify within the producer.

5. The slagging producer is in many respects similar to a small blast furnace and requires more intelligent supervision than the common gas producer.

6. The use of limestone or dolomite as a flux without the addition of blast-furnace slag or some similar substance is unsatisfactory and sooner or later causes chilling of the slag.

7. The high temperatures within the slagging type of producer greatly hasten the deterioration of the brick lining, and make frequent repairs and renewals necessary.

8. Blast-furnace slag being needed for fluxing, the use of the slagging type of producer is limited to localities in which blast-furnace slag is readily and cheaply obtained.

9. The need of using metallurgical coke as fuel practically eliminates the slagging producer from consideration for most industrial

uses.

The investigation of slagging gas producers was conducted by C. D. Smith, engineer, aided by F. E. Woodman, assistant engineer.

USE OF COKE AS DOMESTIC FUEL.

An investigation of the possible extension of the use of different kinds of coke as domestic fuel with a view to lessening the production of smoke in cities where high-volatile coals are burned for most purposes is being conducted by C. D. Smith, engineer.

COKING OF COAL AND RECOVERY OF BY-PRODUCTS.

In its efforts to lessen waste of high-grade coals in the manufacture of coke through the use of more efficient devices than the beehive oven and the utilization of lower-grade coals, the Bureau of Mines has kept in touch, through correspondence and inspection of plants, with progress in by-product coking.

The possibility of increasing the manufacture of coal-tar products in the United States and the supply of raw materials therefor was investigated, and a technical paper on the subject, by H. C. Porter, was published.

Small-scale experiments on the low-temperature distillation of coal and the recovery of oils and other by-products were begun. These inquiries were in charge of H. C. Porter, chemist.

STORAGE AND SPONTANEOUS COMBUSTION OF COAL.

On October 1, 1914, the final analyses were made in connection with a 5-year test of the deterioration of high-grade steaming coal used by the Navy Department. The results of these tests and of other storage tests of different coals under various conditions are being compiled for publication. This investigation has been carried out by H. C. Porter, chemist, assisted by F. K. Ovitz, assistant chemist, and later by the general analytical laboratory under A. C. Fieldner, chemist.

Studies of the causes and the methods of controlling spontaneous combustion in stored coal were continued. Several cases of spontaneous fires in the coal stocks of Government establishments were investigated and recommendations for lessening the hazard were made. Careful laboratory experiments were made by S. H. Katz, assistant physical chemist, to ascertain the rate of oxidation of coal and the effect of the size of coal on the passage of air through a pile or a bin of it. The bearing of these factors on spontaneous heating was shown by experiments with large piles of coal, made by H. C. Porter, who investigated the cases of spontaneous heating in coal stocks and had general charge of the investigations.

STUDIES OF OXIDATION OF COAL.

The oxidation of coal at ordinary temperatures was studied in the laboratory at Pittsburgh, by S. H. Katz, in order to ascertain the primary cause of spontaneous heating and deterioration of stored coal, and to find out why different coals vary in ease of ignition.

MOISTURE IN COAL.

In the course of an investigation to determine the mode of occurrence of water in coal, experiments made to ascertain the effect of size of the coal on the draining of the mechanically held water showed that in some instances six or eight times as much water was retained by finely divided coal or slack as by screened lump coal, and that much of the water in coal, the proportion differing with the kind of coal, is held in a state of hydration. This hydrated water is more difficult to remove by drying than free superficial moisture. Results of the investigations were compiled in a technical paper on the water in coal, by H. C. Porter and O. C. Ralston.

INFLAMMABILITY OF COAL DUST.

Ignition of coal dust and other inflammable dusts in air was studied in order to determine whether inflammability depended on the ease of distillation of volatile matter, the ease of oxidation as a whole, or some other property. G. B. Taylor, assistant chemist, made many experiments, in which a cloud of coal dust was momentarily heated. The results have seemed to indicate the amount of distillation that takes place. This investigation is still in progress.

CARBONIZATION OF COAL.

The carbonization of coal in coke ovens and gas retorts and in furnace fuel beds was studied in the laboratory by Mr. Taylor. Some of the results were used in connection with some of the tests of fuel efficiency in boiler furnaces.

INVESTIGATIONS OF PEAT AND LIGNITE.

The investigation of peat is specifically authorized by the act of Congress establishing the Bureau of Mines. The bureau's investigations of both peat and lignite are of especial importance to those people who live remote from good coal fields but near extensive unused deposits of these fuels.

Before the Government's investigation of peat began, little was known of the extent of the peat deposits in the United States or of methods of extracting, drying, and preparing peat, or of the practicability of producing peat fuel at a profit and on a commercial scale. To get definite information about these and related subjects was the aim of the work planned; similar work was arranged for lignites.

Investigations during the past year have therefore continued technical, scientific, and educational work begun in former years. Peat deposits in parts of the country, as Maine and Minnesota, where cooperation was asked by State authorities, were examined and