Perhaps, for the cooler young suburbanite, this will underline his lucky comfort. For the lower income city kid, it's a mirror. Emilio, a Puerto Rican boy slowly getting slower under the stifling heat of his city block, trapped under one of those broiling summer days--with everybody nearly paralyzed, in and outside the tenements, by the need for a breeze. The juvenile release comes with the arrival of a sprinkler truck and Emilio and his friends rush into a wild splashing, cooling respite. Chicago had a riot that started over disputed hydrant water for children...The unholy heat comes over in the words and pictures here, a mood book that gets the mood across.