Secretary of the Interior in regard to the use of explosives in those mines.

Examinations and tests of mining explosives in order to increase safety and efficiency in use are important features of the bureau's efforts to prevent coal-mine explosions and safeguard miners. During the fiscal year 2,071 explosives were examined. Nearly 22,000,000 pounds of explosives approved by the bureau as permissible for use in gaseous or dusty coal mines were used in the calendar year 1915, as compared with 2,000,000 pounds in 1908, the year in which Government tests of mining explosives began. The use of these permissible explosives in gaseous mines is required by the laws of several coal-mining States.

As a result of the bureau's investigations, approved electrical switches and motors and approved lamps for miners, the use of which will greatly lessen the danger of mine explosions, are now being manufactured; also several States have enacted stricter laws regarding the use of electricity in mines.

Fuel investigations.-In its efforts to increase efficiency in the use of mineral fuels the bureau is studying the properties of these fuels and the methods of burning them in furnaces and gas producers. Also it is collecting, analyzing, and testing samples of coal purchased under specifications for Government use. In the fiscal year 1916 the aggregate cost of the coal represented by these samples was $7,800,000. During the year the bureau continued to assist, in the capacity of a consulting fuel engineer, various departments and establishments of the Government in solving problems relating to the purchase of fuel and the efficient use of fuel for heating or power. The results of the bureau's investigations are being embodied in reports that are meeting a widespread demand for authoritative information on the utilization of fuel.

Problems of mineral technology. The mineral technology investigations of the Bureau of Mines cover the minor metals, the rare and the precious metals, the metalloids and the nonmetals, brass and other nonferrous alloys, abrasives, cement, mineral products used as building materials, and many different minerals used in the arts. In the United States 75,000 persons annually die of cancer. Through the radium investigations of the bureau, in cooperation with the National Radium Institute, two great hospitals obtained during the year a goodly supply of radium for the treatment of that disease. Low-grade radium-bearing ore, heretofore wasted, was concentrated successfuly in a mill especially designed for the purpose. This concentrate, as well as high-grade carnotite ore, is being treated at the Bureau of Mines plant at Denver, which is now producing radium at the rate of 5 grams a year. The cost of production since operations began in June, 1914, has been less than $40,000

a gram, as compared with a market price of $100,000 to $120,000 a gram. This radium is not sold but is to be used in the treatment of

cancer.

Incidental to the production of radium at the Denver plant many tons of iron vanadate that can be used in the manufacture of highgrade vanadium steel, and many tons of uranium oxide, used in coloring glass and making tool steel, have been produced. For an expenditure of less than $35,000 the Bureau of Mines will receive as its share of the results of the cooperative agreement at least $100,000 worth of radium.

In normal times the metal losses in brass melting in the United States annually amount to $3,000,000, and during the past year of high prices and large production have probably been nearer $10,000,000. As a result of its investigations of these losses the Bureau of Mines has devised an improved electric melting furnace which will be thoroughly tested on a commercial scale during the coming year. Also, because of the excessive loss of metal, sometimes running as high as 40 per cent, in melting scrap aluminum, the bureau ' has investigated methods of melting aluminum chips and is publishing the results.

In its clay-industry investigations the bureau has studied methods of so treating the secondary kaolins found in almost unlimited quantities in the Coastal Plain region of Georgia and the Carolinas as to render them applicable to the production of white wares. The results have demonstrated that these kaolins can be cheaply purified and that the purified material is superior to the best English china clay for making china, white crockery ware, and white tile.

Increasing efficiency and lessening waste in the petroleum and natural-gas industries.—Through its petroleum division the Bureau of Mines is investigating problems of technology, engineering, and chemistry in the production and utilization of oil and gas. The petroleum-technology investigations deal chiefly with practicable methods of eliminating waste in drilling wells and of recovering a larger proportion of the oil or gas stored in the productive sands; the engineering-technology investigations deal with storage, the prevention of losses from fires, and the manufacture of gasoline from natural gas; and the chemical-technology investigations deal with the mechanical development of the Rittman process for manufacturing gasoline, toluene, and benzene, and the improvement of methods for analyzing and testing petroleum and petroleum products.

Operators in different fields have been shown the need of properly protecting oil and gas sands from infiltrating water and of sealing wells so as to confine the natural gas securely until such

time as it is utilized. Also, the bureau demonstrated the advantages of using mud fluid in drilling wells. Operators in Kansas and in the Blackwell field of Oklahoma are successfully using methods the bureau advocates. In the Blackwell field the operators should recover at least 80 per cent of the gas in the gas sands, whereas in older fields the recovery has been less than 10 per cent. A conservative estimate of the value of the gas that will be saved through the use of approved methods in the Blackwell field is $20,000,000.

The bureau is cooperating with the Bureau of Indian Affairs in the supervision of oil and gas operations on Indian lands.

Mechanical details of the Rittman process for making gasoline, benzene, and toluene were perfected during the year and the process was shown to be successful on a commercial scale. Tests have indicated how cheaply gasoline can be made from stove distillate.

Various gasolines sold in this country in 1915 were tested to determine their value as motor fuel. Other investigations included the production of gasoline from natural gas and the examination and analysis of petroleum.

Study of metallurgical problems.-In its metallurgical work the bureau continued to cooperate with the Selby and Anaconda smelter commissions, and during the year published as a bulletin the comprehensive report of the Selby Smelter Commission on alleged nuisance and damage occasioned by the Selby smelter in California. Especial attention is being given to the removal of sulphur from smelter gases. Cooperative work with the Anaconda Smelter Commission in the improvement of smoke conditions at the Anaconda smelter in Montana has led to the construction at the smelter of the first units of an electrical apparatus for treating smoke and to the operation of the first units of a sulphuric-acid plant that is to have a daily capacity of 140 tons of acid. Studies to effect the utilization of the acid in the manufacture of phosphates in Montana are in progress.

Under a cooperative agreement with the University of California the bureau has established a mining experiment station at Berkeley, Cal., where it is investigating problems relating to the smelting of lead and copper ores. Some of these problems are the absorption and purification of the sulphur dioxide in smelter smoke and the reduction of the gas to elemental sulphur by the wet Thiogen process. A study of the reduction of barium sulphate, a substance used in making paints and in various chemical industries, was completed.

Other work at Berkeley includes investigation of the improvement of the cyanide and other hydrometallurgical processes for

treating ores of gold through the study of the efficiency of machines. for crushing ores, the settling of slimes, and the behavior of aluminum in cyanide solutions.

Investigations at the Salt Lake City experiment station, conducted in cooperation with the University of Utah, deal chiefly with methods of preventing wastes in the concentration and metallurgical treatment of nonferrous ores, especially ores of lead and zinc, with the purpose of making available as ore the great bodies of material now considered waste. Encouraging results have been obtained in the treatment of lead ores by a chloridizing roast and leaching with a solution of common salt, in a volatilization process for treating oxidized ores of zinc, and in investigations of the flotation process for concentrating ores.

An investigation of hazards at blast furnaces in Pennsylvania was made in cooperation with the Pennsylvania Department of Labor and Industry. The dangers peculiar to work about Bessemer converters and open-hearth furnaces at steel plants have been investigated, and an investigation, in cooperation with the Federal Public Health Service, of health conditions in the steel and metallurgical plants of the Pittsburgh district was completed.

Comprehensive studies of the corrosion of metals in mines, with especial reference to damage to mining equipment and the corrosionresisting qualities of various metals were continued through the year.

Investigation of the fluidity of blast-furnace slags, one purpose of which is to furnish metallurgists and furnace men with reliable data for use in smelting lean and complex ores, is being continued, and the results are being published. A new high-temperature viscosimeter has been developed by which the viscosity of slags can be accurately measured to a temperature of 2,900° F., or about 900° higher than the highest temperature previously used in viscosity measurements of any substance.

In cooperation with the State School of Mines of Missouri, the bureau is continuing a study of the milling of lead and zinc ores in the Joplin district. Mo., with particular reference to milling losses and the possibilities of treating the ores by flotation.

Chemical researches. In addition to the chemical investigations already mentioned, the bureau studied the composition and properties of mine gases and natural gas. The investigations included an absorption method of extracting gasoline from natural gas which, if generally applied, will make possible the recovery of 100,000,000 gallons of gasoline from natural gas each year; the errors that may arise in commercial methods of measuring natural gas at high pressure; the perfecting of a gas detector for use in mines and other places; methods of gas analysis; the chlorination of natural gas

with a view to making tetrachloride, chloroform, and other valuable products; and the fusibility of coal ash as related to the formation of clinker in fuel beds.

Other investigations.-Special investigations that were described in reports published during the year or are stil. in progress include placer-mining methods, especially the use of gold dredges; iron-ore mining and iron making in the United States; utilization of lowgrade fui; gas-producer practice; and factors controlling the use and the market prices of fuel.

SOME URGENT NEEDS OF THE BUREAU.

Coal and metal mining investigations.-Additional funds are needed to carry on certain mining investigations that demand attention. Some of these investigations are as follows:

Ventilation of metal mines, a complex problem, some phases of which are still unsolved even by operators of large mines, should receive detailed study. The health of a large number of metal miners is being impaired by the character of the air that they breathe in deep or remote workings.

Subsidence, earth pressures, and roof supports in mines are of so much importance in both coal mining and metal mining, as well as in various engineering enterprises, that investigations should be made to include the testing of roof supports and the compressibility of rock and ore. Because of the complexity of the problem an engineer skilled in the application of higher mathematics should be engaged to work with other investigators.

Explosives intended for use in metal mines and quarries should be tested in order to determine the conditions under which they can be used with least danger to the health and safety of miners. Buildings should be provided at the bureau's experimental mine for carrying on this work.

Sinking of shafts and driving of tunnels.-The driving of tunnels under bodies of water, the sinking of shafts through waterbearing strata, and the special methods to be used are problems of much importance. Serious accidents in driving tunnels for water supply or for transportation purposes at different cities emphasize the need of thorough investigation of these problems.

Petroleum investigations.-Adequate funds for conducting investigations relating to petroleum and natural gas are urgently needed. In the calendar year 1915 more than 281,000,000 barrels of petroleum, valued at $180,000,000, was produced in the United States, more than 65 per cent of the total output of the world. However, the petroleum resources of this country are not unlimited, and the demand for gasoline and other products is bound to increase. It is