In connection with all these lines of fuel testing, certain research work, both chemical and physical, is carried on to determine the true composition and properties of the different varieties of coal, the changes in the transformation from peat to lignite, from lignite to bituminous coal, and from bituminous to anthracite coal, and the chemical and physical processes in combustion. Experiments are conducted concerning the destructive distillation of fuels; the by-products of coking processes; the spontaneous combustion of coal; the storage of coal, and the loss in value in various methods of storing; and kindred questions, such as the weathering of coal. These experiments may yield valuable results through careful chemical research work supplemented by equally careful observations in the field. _Inspection and Mine Sampling._--In the Geological Survey Building, at Washington, coal purchased for Government use on a guaranteed-analysis or heat-value basis, is inspected and sampled. Some of the employees on this work are constantly at the mines taking samples, or at public works inspecting coal for Government use, while others are stationed at Washington to look after the deliveries of coal to the many public buildings, and to collect and prepare samples taken from these deliveries for analysis, as well as to prepare samples received from public works and buildings in other parts of the country. [Illustration: Fig. 10. COAL-SAMPLING ROOM, GEOLOGICAL SURVEY, WASHINGTON, D.C.] The preparation of these samples is carried on in a room in the basement of the building, where special machinery has been installed for this work. Fig. 10 shows a plan of this room and the arrangement of the sampling and crushing machinery. The crushing of the coal produces great quantities of objectionable dust, and to prevent this dust from giving trouble outside the sampling room, the wooden partitions on three sides of the room (the fourth side being a masonry wall) are completely covered on the outside with galvanized sheet iron. The only openings to the room are two doors, which are likewise covered with sheet iron, and provided with broad flanges of the same material, in order to seal effectually the openings when the doors are shut. Fresh air is drawn into the room by a fan, through a pipe leading to the outer air. A dust-collecting system which carries the coal dust and spent air from the room, consists of an arrangement of 8-in. and 12-in. pipes leading from hoods, placed over the crushing machines, to the main furnace stack of the building. The draft in this stack draws all the dust from the crushers directly through the hoods to the main pipe, where most of it is deposited.