This speech by the eminent British physicist John Tyndall reflects on the nature and significance of scientific inquiry in the 19th century. It covers a range of topics related to science and philosophy, including the role of experiment, the nature of matter, and the relationship between science and religion. With its clear and insightful prose, it offers a compelling perspective on the scientific enterprise for both scientists and general readers. This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work is in the "public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.