Harriet, Harriet,/ Born a slave./ Work for your master/ From your cradle/ To your grave . . . . Harriet, Harriet,/ Born to be free,/ Led her people/ To liberty."" In a text that tells it like a hymn of praise, in paintings that are expressions not illustrations, Harriet Tubman ""grow(s) bigger, grow(s) stronger,"" gets the sign that the time is right, leads her first runaways toward the Promised Land ""As Moses led his people/ 'Cross the burning sand."" Mr. Lawrence is of course the noted Negro artist whose black people were beautiful twenty-five years ago; in similar flat planes and stripped-down compositions, with telling distortions of size and perspective, he has created a sequence of scenes that are arresting, discomfiting, sometimes confusing. (Most of the confusion is intentional, a matter of losing the runaways in the landscape.) Certainly they will be controversial. It remains to be seen whether art as rigorous, as unpretty, as this will work in a picture book -- except that this is not entertainment or even instruction for little children, it should be shared with groups of all ages.