Intimate contact with Nature, which, because of the artificial conditions of city life and of traditional education, few children can know, had a decisive influence on Pierre's development. Guided by his father, he learned to observe facts and to interpret them correctly. He became familiar with the animals and plants of the environs of Paris. He knew which ones could be found at each season of the year in the forests and fields, the streams and ponds. The ponds in particular had for him an ever new attraction with their characteristic vegetation and their population of frogs, tritons, salamanders, dragonflies, and other denizens of air and water. No efforts to obtain the objects of his interests seemed too great for him. He never hesitated to take any animal in his hands in order to examine it more closely. Later, after our marriage, in our walks together, if I made some objection to letting him put a frog into my hands, he would exclaim: "But no, see how pretty it is!" He loved always, too, to bring back bouquets of wild flowers from his walks. Thus his knowledge of natural history progressed rapidly. At the same time, also, he was mastering the elements of mathematics. His classical studies, on the contrary, had been much neglected, and it was principally through general reading that he acquired a knowledge of literature and history. His father, who was widely cultured, possessed a library containing many French and foreign works. Having himself a very pronounced taste for reading, he was able to communicate it to his son. When he was about fourteen years old, a very happy event occurred in Pierre's education. He was put under an excellent professor, A. Bazille, who taught him elementary and advanced mathematics. This master was able to appreciate his young pupil, became much attached to him, and directed his work with the greatest solicitude. He even helped him to advance in his study of Latin, in which he was very much behind. At the same time Pierre and Albert Bazille, his professor's son, became friends. This teaching had, I am sure, a great influence on the mind of Pierre, aiding him to develop and to sound the depth of his faculties and to realize his capacities for science. He had a remarkable aptitude for mathematics, which expressed itself chiefly by a characteristic geometric spirit and a great power of spatial vision. He, therefore, progressed rapidly and joyfully in his studies under M. Bazille, for whom he always felt an unalterable gratitude.