JIM SUHRST. LOUIS (AP) â¿¿ Arch Coal Inc., one of the world's biggest coal producers, is scheduled to report earnings for the third quarter before the market opens on Friday. WHAT TO WATCH FOR: Analysts may be especially interested in Arch's performance in recent months because of the headwinds coal miners have faced from weaker demand in the global economy. The coal industry and its stocks have been battered as utilities switched to cheap natural gas from coal to generate electricity. Natural gas prices earlier this year reached the lowest levels in years because of booming production. Lately those prices have risen, buoying optimism that power plants increasingly will switch back to coal. Arch's latest earnings may reflect its June announcement that it was laying off about 750 workers in the Kentucky, Virginia and West Virginia coalfields. Arch blamed the move on market pressures and a challenging regulatory environment that it said has pushed U.S. coal consumption to a 20-year low. Among the first of the coal sector's big players to report each quarter, rival Peabody Energy â¿¿ the world's biggest private-sector coal company â¿¿ on Monday said its third-quarter profit plummeted 84 percent, marking the third quarter in a row it posted lower net income. But the company, which had adjusted results for the July-September period that still topped Wall Street expectations, said it sees the global market stabilizing. Peabody projected that U.S. coal demand will decline by about 120 million tons this year but insisted that most of that drop-off already has happened. Arch this week got a legal victory in Montana, where the state's Supreme Court ruled that a board headed by the governor didn't violate the state Constitution when it leased 587 million tons of coal without an environmental review. But the high court, affirming a lower court ruling in a lawsuit brought by the Sierra Club and other groups, found that environmental studies still must take place before Arch can mine more coal.