Jack McCallum didn't mention the most unusual and, I think, the most interesting fact about Spearfish, S.Dak., in his account of An American Summer (A Vacation from a Vacation, July 31). Spearfish experienced the steepest rise of temperature in the shortest period of time ever recorded. On Jan. 22, 1943, at 7:30 a.m. the temperature was—4� F. By 7:32 a.m. it had risen to 45�. At 8:45 a.m. the temperature was 55�, and within 42 minutes it had dropped again to -4�. According to a weather observer on that day, Roland R. Hamann of the U.S. Weather Bureau in Rapid City, the wildly fluctuating temperature was the result of an "air-mass discontinuity," or a strong change in wind direction. That day's weather graph (left) is on display at the Montana-Dakota Utilities Co., a few blocks from the Spearfish fish hatchery.
R.L. TUNSTALL Trumbull, Conn.