These movements of science have produced a copious literature which has not enjoyed the same attention and reading as imaginative books, because, once the ideas are known and incorporated into the existing body of scientific knowledge, these scientific writings tend to acquire chiefly an historical interest. Yet they are monuments of the advance of civilization, and deserve a better fate. Many of them are still interesting to read as human documents because they illustrate how painfully and slowly man’s exact knowledge of verifiable phenomena has been accumulated. No one outside of the small company of highly trained scientists can read all of them through, yet most of them have sections which are as readable and as exciting as any modern novel. It is the purpose of this book to present to the young college student and to the general reader some of the more representative of these classics in the literature of science, bringing together in this convenient form at least some reminders of a vast field of reading where one may browse for a lifetime with interest and profit. If it be used in conjunction with a history of science it will readily supply a vivid sense of the movement of the mind of western civilization, increasing in us a respect for the effort of our ancestors, and inspire us to encourage and to forward the work of contemporary scientists, and restrain us at least from hindering them in their efforts. Although the selections may be used as a textbook in courses like Introduction to Modern Civilization, Philosophy, and The History of Science now given in the more progressive colleges and universities, it may also profitably be used as a text for freshman or sophomore readings in English courses given in colleges predominantly technical or scientific, like Engineering, Agricultural, and Forestry Colleges. In those English courses where emphasis upon ideas is made to provide the inspiration for writing, these selections will be found, as I found them in my own work, to stir up considerable discussion and to provide opportunities for reading modern scientific literature. Moreover, the literary style of science at its best will be found to be excellently illustrated in these straightforward, coherent sentences written by some of the world’s clearest thinkers. They illustrate concretely what Tyndall remarked in his closing words of the famous _Belfast Address_: “It has been said that science divorces itself from literature. The statement, like so many others, arises from lack of knowledge. A glance at the less technical writings of its leaders--of its Helmholtz, its Huxley, and its Du Bois-Reymond--would show what breadth of literary culture they command. Where among modern writers can you find their superiors in clearness and vigor of literary style? Science desires no isolation, but freely combines with every effort toward the bettering of man’s estate. Single-handed and supported not with outward sympathy, but by inward force, it has