Whether in the laboratory of the chemist or the physicist, in the machine shop or the engine-room, every means of measurement must be based on standards created with the highest skill and guarded with the utmost care. For the United States these ultimate standards, in full variety, are brought together at the Bureau of Standards at Washington, of which Dr. S. W. Stratton is director. Here are safeguarded copies of the international metre and the kilogram adopted by Executive Order in 1893 as fundamental units of length and mass; here, too, are standard yards and pounds, bearing fixed legal relations to the international metre and kilogram. The Bureau is prepared to determine the length of any standard up to fifty metres, to calibrate its subdivisions, and to determine its coefficient of expansion for ordinary temperatures. To the credit of American workmanship be it said that at times the micrometers received from leading manufacturers, for use in workshops of the best class, are so refined in their measurements as to tax to the utmost the resources of the Bureau. Its precision balances, by Rueprecht of Vienna, and Stuckrath of Berlin, weigh a kilogram within 1/200 part of a milligram, that is, within one two-hundred-millionth part of its load. In the department of electricity a resistance may be measured all the way from 1/100,000 of an ohm to 100,000 ohms. Here are voltmeters, and wattmeters of the best types. Magnetism, as swiftly summoned or dismissed in the cores of dynamos and motors, is here measured with the utmost exactitude. In some of the instruments fused quartz has been used as a means of suspension because its high elasticity and great strength allow it to be drawn as extremely fine threads. Dr. K. E. Guthe, now of the University of Iowa, while at the head of the section of magnetic measurements, found that fibres equally serviceable may be drawn from steatite, or soapstone, such as forms a common kind of gas-burner. Thick quartz threads break easily when bent, those of steatite do not. In thermometry, a section in charge of Dr. Waidner, much work goes forward in testing clinical and other thermometers for manufacturers. The whole range of heat measurement is covered by instruments adapted to recording the highest attainable temperatures until we reach apparatus by which, through observation of its light, the absolute temperature of the electric arc has been found to be 3720° C. Measurements of light proceed in another section. Here a photometer designed by Mr. Edward P. Hyde, of the Bureau staff, has reached the hitherto unexampled accuracy of one part in 200. The Bureau has an extensive workshop where new designs for improved apparatus are constantly in hand. For services on behalf of the national or any state government the Bureau makes no charge; moderate fees are required from firms and individuals. In its new and adequate quarters the Bureau is doing work as authoritative as that of any similar institution in the world.