At just before 10 p.m. on Tuesday, April 20, 2010, the Transocean Ltd.-owned and BP Plc.-operated floating oil rig Deepwater Horizon was boring an exploratory well in the Macondo Prospect—about 40 miles southeast of the Louisiana coast and nearly a mile underwater—when it exploded without warning from a well blowout. …BP has tried repeatedly to stop the flow, to no avail. (As of this writing on Tuesday evening, July 13, it remains to be seen whether the well cap installed last night, a Band-Aid pending completion of the long-awaited relief wells next month, will actually work.) The spill’s magnitude has beggared description or belief.