ceramic chemist, who succeeded Robert Back, resigned, in cooperation with potteries in Ohio. The results will be published in a special report.

QUARRY TECHNOLOGY.

Nearly all the active marble quarries in the United States as far west as central Colorado were investigated, 64 being visited. Cooperative arrangements were made with the United States Geological Survey, the Bureau of Standards, and the Office of Public Roads. Representative marble specimens each weighing approximately 250 pounds, were taken from various quarries and shipped to the Bureau of Standards for testing. The investigations were directed toward two principal objects: (1) Increased safety in stone quarries and a consequent reduction in quarry accidents; (2) increased efficiency in marble quarrying and the elimination and utilization of waste.

Records of the causes of numerous quarry accidents in previous years were obtained, and from the information thus gained, and from examination of conditions in about 100 active quarries it was possible to determine the most prolific sources of danger and the means by which danger may be minimized. Various safety precautions, including the maintenance of machinery, equipment, and quarry walls in proper condition, are suggested, and their need emphasized in a report now in press.

Rock structure and rock imperfections vary greatly from place to place. Every limestone quarry can not be worked in the same way, and, to obtain the highest efficiency, methods must be modified to suit prevailing conditions. Great improvements in methods are possible at most quarries. An encouraging feature of the work is a strong and almost universal demand from quarry operators for information concerning the methods and conditions in the numerous quarries that they are unable to visit. To satisfy this demand a report has been prepared dealing with the varying problems that confront the quarry operator, and describing the different methods and types of machinery that will meet requirements in the most efficient and economical manner.

"Strain breaks" in marble quarries have received special attention. These irregular fractures resulting from rock stresses have caused heavy losses in a number of quarries. Through a study of conditions, and the cooperation of a marble company, a method has been devised of relieving the rock pressure so as to prevent destructive fracturing. As a consequence, great masses of valuable marble that otherwise would be wasted are now utilized.

Investigations of a similar nature to those outlined above are to be conducted during the coming year in the structural limestone and sandstone quarries of the country.

These quarry investigations are in charge of Oliver Bowles, quarry technologist.

WORK OF FUELS AND MECHANICAL-EQUIPMENT DIVISION.

The fuels and mechanical-equipment division is under the supervision of O. P. Hood, chief mechanical engineer, with headquarters at the Pittsburgh experiment station. The organization of the division has been given elsewhere in this report (p. 28).

During the fiscal year 1915 the work of the division included the preparation of plans for engineering laboratories and a power plant for the new buildings at Pittsburgh and the general direction of investigations relating to the utilization of fuels and to safety in mine equipment.

During the year the value of the purchase of coal on a specification basis, when conducted within the limitations determined by experience, has been more fully demonstrated. The bureau has rendered increasing assistance to other Government bureaus and departments as they have become aware of the aid it can give in any problem involving the more efficient use of fuel in Government plants.

Information that points to more rational designs for furnaces and more economical control of furnace fires has been obtained from a study of the combustion processes within and above the burning coal. Work on the problem of increasing the efficiency of heat transmission in steam boilers has begun. Investigation of electrical methods of precipitating smoke has shown that they are not sufficiently developed for practical use.

The bureau's engineers have concluded, after considerable investigation, that the slagging type of gas producer will not furnish a general means of utilizing bony coal and coal high in ash.

Believing that the substitution of approved electric lamps for open lights in all coal mines will greatly lessen the danger of fires and explosions, the bureau's engineers have cooperated with makers of miners' electric lamps in the effort to direct the rapid evolution of safe, efficient, and practicable lamps, approving such as meet the bureau's specifications.

Similar cooperation has been given the development of explosionproof motors and other electric equipment for mines.

MINE-EQUIPMENT INVESTIGATIONS.

During the year study of the problem of safety in mine equipment took such direction as the limited laboratory facilities at the Pittsburgh experiment station made necessary. The results of investigations of the effect of the exhaust gases from a gasoline mine locomotive on the health of miners, especially the limitations as to the size of engine and the condition of operation, were transmitted for publication.

A study of coal-mine hoisting equipment with especial reference to safety in handling men was begun, the construction, operation, and inspection methods of safety catches on mine cages being noted in an investigation that has covered most of the principal eastern coal fields. Supplementary data were collected on the other factors of the problem of safety in hoisting men.

Mechanism has been designed for use on mine-rescue cars for lighting, charging batteries, and pumping oxygen into containers, for certain equipment in exhibits at the Panama-Pacific Exposition, and for numerous devices used in special investigations.

The mine-equipment work and investigations mentioned was in direct charge of O. P. Hood, chief mechanical engineer.

DEVELOPMENT OF IMPROVED BREATHING APPARATUS.

Rescue crews have to do hard work in the poisonous atmosphere of a mine after an explosion or fire, and the breathing apparatus

they wear must be of the best design and construction. It must be absolutely reliable, must supply an artificial atmosphere of great purity, must be as light as is consistent with strength, and should impede the movements of the wearer as little as possible.

With a view to devising apparatus better than that of foreign make now used, investigations have been carried on at Columbia University, New York, by W. E. Gibbs, engineer of special research. Dr. Yandell Henderson, consulting surgeon, acted in an advisory capacity.

Such a breathing apparatus, a self-contained unit carried wholly on the back of the user, has been developed during the past year by Mr. Gibbs. It is light and its parts are well protected against injury.

By means of a special device oxygen is fed at the rate it is used, and although plenty is available for the wearer when working hard none is wasted when he is resting. Hence the new apparatus may be worn for a considerably longer time without recharging than models now in use. An unusually efficient carbon dioxide absorber that liberates little heat is another feature of the apparatus. Caustic soda, which is much cheaper than the potash salt formerly thought necessary, is used as the absorbent.

As a result of this investigation the United States will soon be independent of foreign makers of breathing apparatus, and the apparatus made in this country will be much better than any available when the investigation began.

Work on a portable electrolytic oxygen generator for use on the rescue cars has progressed enough to show that the cars can be made independent of outside sources of oxygen and that considerable economy will result from the use of the generator.

ELECTRICITY IN MINES.

Investigations relating to the use of electricity in mining and the other mineral industries are made part of the duties of the Bureau of Mines by the terms of its organic act. The purpose of these investigations is to devise and to point out methods for lessening danger from explosions, fires, or shock.

PORTABLE ELECTRIC MINE LAMPS.

During the year the bureau's electrical engineer and his assistants continued investigation of portable electric mine lamps, devising and conducting tests for safety and for practicability. Lamp manufacturers submitted 10 lamps for test. Two of these were rejected without test, one was rejected after complete tests had been made, one was approved, the tests of five others are nearly completed, and the tests of one lamp have not yet been started.

The design and construction of all these lamps were more or less changed by the manufacturers to conform with the bureau's requirements and suggestions. Many conferences were held with lamp manufacturers in the endeavor to assist them in their work.

During the year much information relative to portable electric lamps has been collected, and as a result the bureau completely revised its requirements and published them in Schedule 6A. As a consequence of the bureau's work several desirable improvements

have been made in the design of the lamps, notably those assuring a wider stream of light and more uniform illumination.

Probably the greatest advance through the bureau's efforts has been the improvement of the lamp bulbs, an advance made possible by the cooperation of the principal makers of bulbs in this country, who have agreed to make bulbs according to the bureau's specifications. The bureau's method of testing portable electric lamps has been improved and practically standardized.

The work on electric lamps was carried on by L. C. Ilsley, assistant electrical engineer, and R. W. Crocker, junior electrical engineer.

ELECTRIC SHOT FIRING.

In the coal mines on the segregated Indian lands in Oklahoma, the Secretary of the Interior has, as a result of representations made by the bureau, required the use of outside shot-firing systems or the use of permissible explosives. In this connection outside shot-firing systems in use were examined to ascertain the feasibility of using them in Oklahoma, and operators who were interested in installing such systems were interviewed. Many tests were made, and a report on existing conditions, with recommendations as to outside shot-firing systems, was submitted to the mine operators of Oklahoma. A report on outside shot firing was also submitted for publication by the bureau.

The field work was done by N. V. Breth, mine electrician, and the work at the Pittsburgh station by H. H. Clark, electrical engineer.

EXPLOSION-PROOF MOTORS.

The first motor submitted to the bureau for test and approval for use in gaseous mines was finally approved in October, 1914, after the manufacturer had made extended changes in accordance with the bureau's suggestions.

As no other motors had been submitted at the time that the test of the first motor was completed, all work on explosion-proof motors was stopped. Six more applications for test were received later, but lack of funds prevented the opening of the investigation during the year. Funds are available for tests in the coming year. The work has been done by R. W. Crocker, junior electrical engineer. A technical paper on permissible explosion-proof motors by H. H. Clark, electrical engineer, was published by the bureau.

RULES FOR THE INSTALLATION AND USE OF ELECTRICITY IN MINES.

Much time has been given to drafting a proposed set of rules for the use of electricity underground. The first draft, prepared by C. M. Means, consulting engineer, was completed, sent out for criticism, revised, and sent again for criticism to representatives of the American Institute of Mining Engineers, American Institute of Electrical Engineers, the Mine Inspectors Institute of America, and various manufacturers and mine operators.

OTHER ELECTRICAL WORK.

Among miscellaneous activities of the electrical engineer and his assistants are the following:

Supervision of the portable electric lamps at the bureau's experimental mine, development of a storage-battery lamp for rescue

parties, experiments with a methane detector, tests of gas-filled lamps in the presence of methane, and designing of equipment for the electrical laboratory under construction. A technical paper on electric lights for use about oil and gas wells, by H. H. Clark, electrical engineer, was published.

INSPECTION OF GOVERNMENT FUEL PURCHASES.

The work of fuel inspection is under the immediate direction of G. S. Pope, engineer, assisted by P. M. Riefkin and N. H. Snyder, assistant engineers, and D. M. Obler, J. B. Riefkin, and M. M. Shaw, junior engineers, all with headquarters in Washington. A junior fuel engineer was temporarily stationed in New York City and another at Norfolk, Va., to inspect coal shipments for the Isthmian Canal Commission and the Panama Railroad Co.

The purchase of coal by the Government under contracts that specify the heating value, the ash and the moisture content, and other factors was first adopted in 1906. Now, the plan, variously modified in form but the same in principle, has been adopted by all departments of the Government, and is applied to almost all contracts large enough to warrant samplying and analysis and tests of heating value. The aggregate cost of fuel purchases for the Government under specifications prepared by the Bureau of Mines is now approximately $4,800,000 per annum, and the cost of additional fuel bought under the general advice of the bureau aggregates some $3,000,000 per annum more, making a total value of not less than $7,800,000.

As the specification method had been generally adopted prior to the beginning of the fiscal year, the number of tons of coal purchased under contract for the fiscal year under specifications prepared by the Bureau of Mines did not show any marked increase, and the status of work done was about the same as in the year before, but the simplifying of specifications and the improving of methods of sampling and analysis were given particular consideration.

During the year, 7,527 samples of coal were received for analysis. The work of fuel inspection includes the collection, analysis, and testing of samples representing coal purchased for the Government under specifications in order to ascertain whether the deliveries conform to the contract stipulations. In such a contract a bidder guarantees the quality of the coal he offers, and the quality guaranteed by the successful bidder becomes the standard of his contract. Analyses of samples of deliveries determine whether the coal delivered is of the guaranteed standard. If it is not, the price to be paid is proportionately decreased; if the coal is of higher quality, the price is proportionately increased.

A number of the States, many of the larger cities, and a large number of corporations and business concerns in different parts of the country have followed the general plans adopted by the Government for the purchase of its coal.

During the year a considerable number of samples of coal from the States of New York, Indiana, Minnesota, and Maryland were analyzed and tested. Authority for doing such work for State governments is given by the new organic act of the bureau.

At the request of the Navy Department, the mining and shipping facilities of mines from which purchase of coal for that department is proposed are carefully examined by engineers of the bureau, and