New York Times: Children at a day camp near here were pulled from the swimming pool once an hour so the lifeguards could plunge in and cool off. Commuter trains in Washington were slowed because of overheating tracks. Horse-racing tracks were closed in Philadelphia and Wilmington, Del. Up and down the Eastern Seaboard on Tuesday, safety concerns upended the usual routines as a brutal blast of heat brought temperatures in excess of 100 degrees in several cities, with little relief expected for days to …