填空题. A．principal B．lubricating C．yield D．Crude E．substitute F．collecting G．surplus H．impractical I．smelting J．gathering K．produce L．rivaled M．competed N．petroleum O．Coarse An important new industry, oil refining, grew after the Civil War. 11 oil, or petroleum, a dark, thick ooze from the earth had been known for hundreds of years, but little use had ever been made of it. In the l850s, Samuel M. Kier, a manufacturer in western Pennsylvania, began 12 the oil and refining it into kerosene. Refining, like 13 , is a process of removing impurities from a raw material. Kerosene was used to light lamps. It was a cheap 14 for whale oil, which was becoming harder to get. Soon there was a large demand for kerosene. People began to search for new supplies of 15 . The first oil well was drilled by E. L. Drake, a retired railroad conductor. In 1859 he began drilling in Titusville, Pennsylvania. The whole venture of drilling seemed so 16 and foolish that onlookers called it "Drake's Folly". But when he had drilled down about 70 feet (21 meters), Drake struck oil. His well began to 17 20 barrels of crude oil a day. News of Drake's success brought oil prospectors to the scene. By the early 1860s these wildcatters were drilling for "black gold" all over western Pennsylvania. The boom 18 the California gold rush of 1848 in its excitement and Wild West atmosphere. And it brought far more wealth to the prospectors than any gold rush. Petroleum could be refined into many products. For some years kerosene continued to be the 19 one. It was sold in grocery stores and door-to-door. In the 1880s and 1890s refiners learned how to make other petroleum products such as waxes and 20 oil. Petroleum was not then used to make gasoline or heating oil.