With the soil samples from various fields arranged in neat piles on the white paper Grant set to work on matters which were, for the most part, mysterious to the farmer. A Bunsen burner was connected with the chandelier in the room. Small portions of the soil from each pile were placed in separate test tubes. Then each was heated, mixed with small portions of the matter from the various bottles and packages which had been gotten at the drug store. Each test tube was treated in identically the same way and as he finished with each one Grant entered figures in his note book. He was working on the last tube when a knock came on the door, and in response to Grant's "Come" the door opened and Dixie Mason entered. The little Secret Service operative remained silent while Grant finished the test tube. He jotted some figures in his note book, then snapped it shut, and turned toward her smiling. "You have discovered something?" Dixie asked. "I think so," answered Grant. "But first let us hear what you have discovered, to see if it fits in with my find." "It isn't an awful lot," answered Dixie. "In the first place every fire has started in the portion of the field nearest to the road or a railroad, and almost invariably there has been water near the place where the fire started. The only strangers which have been observed in the vicinity were a couple of traveling geologists, who did most of their traveling on foot and carried the samples they had collected in little cloth bags. That is about all." "It is enough," said Grant. "The point of origin of the fire in the first field I examined attracted my attention because it had been burned with a more intense heat than burning grain would make. I took a sample there and then for purposes of comparison took another sample of the soil some distance away. It was easy to determine the place of the origin of the fires in the other fields, for in each place I found a spot where there had been intense heat. The samples from these spots which I have analyzed show a large percentage of phosphorus oxide, while the other samples are free from it. Phosphorus oxide is formed by the burning of phosphorus." "Which makes it very clear as to how the fires started," commented Dixie. "It may be to you," interjected the farmer, "but I can't see what started the phosphorus burning even if some was placed in the field."