What do Thornton and his partners find after a long search? Why does this cause Buck to move toward the Call of the Wild?
Near the end of the narrative of Jack London's Call of the Wild, Thornton and the others find what all the other adventurers to Alaska have dreamed of: "the mother lode." While they have originally been searching for the fabled Lost Cabin mine, their discovery is even more fantastic. In a "shallower place in a broad valley where the gold showed like yellow butter across the bottom of the washing pan," Thornton and the others finally stop. Each day they then bring forth from this mine "thousands of dollars in clean dust and nuggets." They work long and hard days that turn into months, stockpiling the gold in bags of fifty pounds.
Because the men are so busy with their mining, there is nothing for the sled dogs to do but help in the hauling of meat for the camp, so "Buck spent long hours musing by the fire." He notices the fear in the men, too, especially the "hairy man" who can climb trees and peer fearfully out into the wilderness.
And closely akin to the visions of the hairy man was the call still sounding in the depths of the forest. It filled him with a great unrest and strange desires. It caused him to feel a vague, sweet gladness, and he was aware of wild yearnings and stirrings for he knew not what.
Without the occupation of pulling a sled and the interaction with the driver, Buck's natural instincts are given the time and opportunity to arise within him. "Sometimes he pursued the call into the forest, looking for it as though it were a tangible thing...." These irresistible impulses of instinct, having no conflict with the chores of man, become stronger and stronger until Buck responds to this wild call in the forest, springing to his feet and hunting the animals he sees. One night Buck awakens to the atavistic call that lies within him: the howling of wolves. After Buck catches up with the wolf and the wolf's attempts to flee this larger dog prove futile, the wolf finally realizes that Buck means him no harm, so he sniffs Buck's nose in a friendly manner. Buck, then, runs happily with his "wood brother."