All the next year was devoted to work upon “Sharp Eyes,” which appeared in the late autumn of 1891. The intent and scope of the book has been told in the author’s letter to his friend. He puts his purpose succinctly in a paragraph of the introduction, which he quaintly entitled “Through My Spectacles”: “‘Sharp Eyes,’ then, is, in brief, a cordial recommendation and invitation to walk the fields and woods with me and reap the perpetual harvest of a quiet eye, which Nature everywhere bestows; to witness with me the strange revelations of this wild _bal masqué_, to laugh, to admire, to study, to ponder, to philosophize,--between the lines,--to question, and always to rejoice and give thanks.” Meantime, he was hard at work pushing the studies for his botany. With the sketches he was making for this purpose, he was also making more water-colors, sending them to the various exhibitions, and arranging sales of his own. He was at work on new articles for the “Young People” continuing the unexhausted vein he had opened for these pages. For older readers he was beginning the articles on the cross-fertilization of flowers which foreshadowed the wonderful charts and lectures with which he delighted and informed the whole country. He had begun to lecture too, and he notes in his journal, July 23, 1891, “At Mrs. Van Ingen’s suggestion, I have concluded to give a series of ten familiar talks on Nature, covering botany, entomology, and ornithology, two each week.” This was the beginning of successive series of lectures, covering four years. From these home talks his work in this field grew and multiplied. Soon he was lecturing with these amazing charts before the clubs in New York, before colleges and schools, and finally before popular audiences. In the winter of 1893-94, he made the venture of a series of six lectures in Hardman Hall, New York City, which netted him the handsome sum of eight hundred and fifty dollars, and drew from the veteran manager, Major Pond, an expression of wonder: “The news of your success in Hardman Hall is phenomenal. I can assure you that you are the only man in the United States who could have done such a business.” Then the calls began to come from all over the country. The same energy, industry, and genius which he had put into his painting and his writing he threw with increasing intensity into this new work. In 1894 he lectured sixty-four times. His success in the new field was instant and complete. It was as thoroughgoing with scientific folk as it was with the children and the plain people. The press had nothing but wonder and commendations. It was an epoch in the popular presentation of scientific fact and research unequaled since the days of Agassiz.