Appropriate celebration of the centennial of anthracite coal is being considered by the citizens of the town of Plymouth, Pa. In 1807 the first shipment of the "black stone" was made by boat down the Susquehanna River, from Plymouth to Columbia, Pa. This date marks the beginning of the use of anthracite, which, according to records of the United States Geological Survey, was discovered about 1790, but was burned only by the use of blowers and forced draft before 1807. It was the discovery that anthracite must be freed from every impurity and crushed to a uniform size before it could be successfully burned, which started the great industry that this year will probably have an output of 70,000,000 tons. People had become accustomed to burning soft coal, which contained so much gas that lumps of any size could be readily ignited and burned without difficulty. Few would have predicted that, unlike soft coal, which is sent to market as it comes from the mine, hard coal would require preparation for market almost as complicated as the manufacture of flour from wheat. The actual mining of anthracite is only the beginning of a long series of processes which produce the accurately sized pure coal which is so satisfactorily burned to-day in millions of homes and in heating plants of large buildings which must have smokeless chimneys. As it comes from the mines anthracite varies in size from lumps as large as a watermelon to those as small as a walnut. The large lumps are individually examined on benches, by men who are expert in detecting layers of black slate or other impurities which look much like coal and which are unavoidably mined with it. With small axes the lumps are cracked, and every vestige of unburnable material is removed before the coal is passed on to be crushed and sorted, by passing over moving screens, into the numerous sizes ready for loading on the cars. Lumps too small to be separately inspected on the start, are crushed first and screened into uniform sizes, after which boys pick out all the impurities r.s the coal passes slowly in thin layers down long chutes. In some localities considerable dirt adheres to the coal, and in addition to the crushing and sizing it is necessary to subject it to several washings during preparation so that it will be clean and bright and all impurities can be readily seen and removed.