Dr. Leslie was not much of a singer, but he presently lifted what little voice he had, and began to favor Nan with a not very successful rendering of "Bonny Doon." Every minute seemed more critical to the girl beside him, and she thought of several good ways to enter upon a discussion of her great subject, but with unusual restraint and reserve let the moments and the miles go by until the doctor had quickly stepped down from the carriage and disappeared within his patient's door. Nan's old custom of following him had been neglected for some time, since she had found that the appearance of a tall young woman had quite a different effect upon a household from that of a little child. She had formed the habit of carrying a book with her on the long drives, though she often left it untouched while she walked up and down the country roads, or even ventured upon excursions as far afield as she dared, while the doctor made his visit, which was apt to be a long one in the lonely country houses. This morning she had possessed herself of a square, thin volume which gave lists and plates of the nerve system of the human body. The doctor had nearly laughed aloud when he caught sight of it, and when Nan opened it with decision and gravity and read the first page slowly, she was conscious of a lack of interest in her subject. She had lost the great enthusiasm of the night before, and felt like the little heap of ashes which such a burning and heroic self might well have left. Presently she went strolling down the road, gathering some large leaves on her way, and stopped at the brook, where she pulled up some bits of a strange water-weed, and made them into a damp, round bundle with the leaves and a bit of string. This was a rare plant which they had both noticed the day before, and they had taken some specimens then, Nan being at this time an ardent botanist, but these had withered and been lost, also, on the way home.