Foundations of Christianity: From the Beginnings to 1650. By J. Bruce Burke and James B. Wiggins. New York: The Ronald Press Co., 1970. ix + 316 pp. $6.50. - Christianity Through the Thirteenth Century (A Volume in “The Documentary History of Western Civilization,” Eugene C. Black and Leonard W. Levy, General Editors). Edited by Marshall W. Baldwin. New York: Walker and Co., 1970. 431 pp. $10.00. (Available also as a Harper Torchbook, $3.95).