I have said almost nothing about the investigators and teachers of natural science in the United States and Canada. One ought to speak of those great botanists, John Torrey and Asa Gray, the latter the earliest champion in the United States of the Darwinian view of organic evolution. And there is Louis Agassiz (ag'-gah-see), who combined with the intellectual keenness of the investigator wonderful power of inspiration as a teacher. He it was that first aroused the educational leaders of the country to the need of scientific instruction for the masses. He gathered about him in Cambridge a group of special students just after the close of the Civil War, almost all of whom became famous for research and as publicists. His seaside school on Penikese Island, off the Massachusetts coast, in 1873, was the forerunner of all our summer-schools. Spencer F. Baird did much the same service at Washington, founding that body of men who have made history at the Smithsonian Institution, the Fisheries Bureau, and other scientific agencies of the Government prolific in research and in practical benefit to mankind. To these patient, hard-working men we owe not only precious additions to original knowledge, but learned instruction. Most of them have been teachers in our colleges and high schools, leading writers in the best magazines, lecturers to whom we have listened with profit, and the authors of our school books and works of reference. Without their unselfish labors in the search for facts, and the generous gift of their learning to the public, the pleasant matter of our Nature books would rest on the same fanciful foundation as did the fables and wonder-tales of the Middle Ages. _SUPPLEMENTARY READING_ AUDUBON THE NATURALIST, 2 vols; _by Francis Hobart Herrick_. LOUIS AGASSIZ, His Life and Correspondence; _by Elizabeth Carey Agassiz_. A LIFE OF HENRY D. THOREAU; _by F.B. Sanborn_. OUR FRIEND JOHN BURROUGHS; _by Dr. Clara Barrus_. THE STORY OF MY BOYHOOD AND YOUTH; _by John Muir_. JOHN MUIR MEMORIAL NUMBER OF THE SIERRA CLUB BULLETIN, vol. X. [**Asterism] Information concerning the above books may be had on application to the Editor of The Mentor. THE OPEN LETTER [Illustration: HENRY D. THOREAU] [Illustration: Courtesy of Houghton Mifflin & Co. Publishers of Thoreau's Works. THOREAU'S FLUTE, SPYGLASS, AND HIS COPY OF WILSON'S "ORNITHOLOGY"] Some folks living in and near Concord way back in the '50's used to say that Thoreau was a thriftless individual who wasted his time in the woods out at Walden Pond and on the Merrimac River--that he was of little use in the world and would not stick to any job. The world does not know who the folks were that said that, and the world doesn't care very much about them. But the world cares a great deal about Thoreau, and wants to know all about him. * * * * *