The heat laboratory is equipped for the calibration of the thermometers and pyrometers, and electrical and other physical apparatus used by the various sections of the Technologic Branch. For convenience in analyzing materials received from the various purchasing officers attached to the Government bureaus, this work is housed in a laboratory on the fourth floor of the Geological Survey Building in Washington. Large quantities and many varieties of building materials for use in public buildings under contract with the Supervising Architect’s office, are submitted to the laboratory by contractors to determine whether or not they meet the specified requirements. Further examinations are made of samples submitted by superintendents of construction, representing material actually furnished by contractors. It is frequently found that the sample of material submitted by the contractor is of far better quality than that sent by the superintendent to represent deliveries. The needed constant check on deliveries is thus provided. In addition to this work for the office of the Supervising Architect, similar work on purchases and supplies is carried on for the Isthmian Canal Commission, the Quartermaster-General’s Department of the Army, the Life Saving Service, the Reclamation Service, and other branches of the Government. About 300 samples are examined each month, requiring an average of 12 determinations per sample, or about 3,600 determinations per month. The chemical laboratory for testing Government purchases of structural materials is equipped with the necessary apparatus for making the requisite physical and chemical tests. For the physical tests of cement, there are a tensile test machine, briquette moulds, a pat tank for boiling tests to determine soundness, water tanks for the storage of briquettes, a moist oven, apparatus to determine specific gravity, fineness of grinding, etc. The chemical laboratory at Washington is equipped with the necessary analytical balances, steam ovens, baths, blast lamps, stills, etc., required in the routine chemical analysis of cement, plaster, clay, bricks and terra cotta, mineral paints and pigments, roofing material, tern plate and asphaltic compounds, water-proofing materials, iron and steel alloys, etc. At present, materials which require investigative tests as a basis for the preparation of suitable specifications, tests not connected with the immediate determination as to whether or not the purchases are in accordance with the specifications, are referred to the chemical laboratories attached to the Structural Materials Division, at Pittsburg. The inspection and tests of cement purchased in large quantities, such as the larger purchases on behalf of public-building construction under the Supervising Architect, or the great 4,500,000-bbl. contract of the Isthmian Canal Commission, are made in the cement-testing laboratory of the Survey, in the Lehigh Portland cement district, at Northampton, Pa.