. The practice of silviculture : with particular reference to its application in the United States . Forests and forestry. 254 FOREST PROTECTION and Oregon. Climate and forest conditions are responsible for this grouping. Throughout the southern haK of the coun-' try, fires, while prevalent, are of a less severe character. To bring out the location and extent of large fires in the past a map prepared by the United States Forest Service/ showing historic fires, is reproduced. (See Fig 82.). Fig. 82. Map showing the location of the principal historic forest fires which have occurred in the United States since the year 1800. Copied from "Forest Fires," by F. G. Pluramer, Bulletin 117, Forest Service, United Stotes De- partment of Agriculture, page 22. Factors Influencing the Spread and Severity of Forest Fires. — All silvicultural operations should so far as practi- cable be conducted in a manner that will minimize the creation of conditions favorable for the spread of forest fires. Unfortu- nately most of the factors influencing the spread and severity. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.. Hawley, Ralph C. (Ralph Chipman), 1880-. New York : John Wiley & Sons, Inc.