I recall riding alone down the eastern slope one afternoon, while prodigious rivers of cloud--white as wool and soundless as light--descended the canon on my right and spread above the foothills, forming a level sea out of which the high dark peaks rose like rocky islands. This flood came so swiftly, flowed so marvelously and enveloped my world so silently that the granite ledges appeared to melt beneath my horse's feet. At times the vapor closed densely round me, shutting out even the rocks of the trail and as I cautiously descended, I almost bumped astonished steers whose heads burst from the mist as if through a covered hoop. The high granite crags on the opposite side of the ravine took on the shapes of ruined castles seated on sloping shores by foaming seas, their smooth lawns reaching to the foam. At one point, as I came out upon a ledge which overlooked the valley, I perceived my horse's shadow floating on the phantom ocean far below me, a dark equestrian statue encircled with a triple-ringed halo of fire. In all my mountain experiences I had never seen anything so marvelous. At another time while riding up the trail, I perceived above my head a far-stretching roof of seamless cloud. As I rose, coming closer and closer to it, it seemed a ceiling just above my reach, then my head merged in it. A kind of dry mist surrounded me--and for ten or fifteen minutes I mounted through this luminous, strangely shrouding, all pervasive, mountain cloud. My horse, feeling his way with cautious care, steadily mounted and soon we burst out into the clear sunlight above. While still the mist curled about my horse's hoofs, I looked across a shoreless ocean with only Cloud Peak and its granite crags looming above its surface. I describe these two spectacular effects out of many others merely to suggest the splendors which inspired me, and which, as I imagined, enriched the daily walk of the forest guard. "To get into my story some part of this glory, my hero must be something of a nature lover--as many rangers are," I argued, and this was true. Before a man will consent to ride the lonely road which leads to his cabin high in the forest, he must not only have a heart which thrills to the wonder of the lonely places, he must be self-sufficing and fearless. I rode with several such men and out of my experiences with them I composed the character of _Ross Cavanagh_. The actual writing of this novel was begun on my forty-ninth birthday at my desk in the old Homestead, and I started off with enthusiasm notwithstanding the fact that Fuller, who was visiting me at the time, expressed only a tepid interest in my "theme." "Why concern yourself with forestry?" he asked. "No one wants to read about the ranger and his problems. Grapple with Chicago--or New York. That's the only way to do a 'best seller.'"