The U.S. Supreme Court, in a case closely watched by energy companies and thousands of landowners began considering who owns vast deposits of natural gas that are mingled with coal on large tracts of land. In arguments before the U.S. high court, lawyers from Amoco Production Co., now part of BP Amoco PLC and for the Southern Ute Indian tribe sparred over what appears to be simple question: What did Congress mean by "coal" when it wrote certain laws in 1909 and 1910? The answer could determine who owns the rights to billions of dollar's worth of minerals beneath about 16 million hectares in the Western U.S. and Alabama.