SAINT CROIX NOTES: River Mornings, Radio Nights by Noah Adams (Norton: $18.95; 218 pp.) . Noah Adams, host of National Public Radio's "All Things Considered," is an anchor in the best sense of the word: a quiet, gentle, folksy voice that, like the chain securing a ship to the stable ocean floor in a rough sea, gives us something to hold onto while listening to stormy stories of political violence and upheaval. These essays, first read on a public radio program that replaced Garrison Keillor's "Prairie Home Companion," are too relaxed to "get the news from poetry," as William Carlos Williams, one of the author's mentors, put it. But in writing of the pleasures of brushing snow off the cat or of canoeing with his wife in a thick fog, "enclosed in ourselves," Adams succeeds in reminding us of the value of the intimate world, lest it be overshadowed by the real one he reports on the radio.