This volume gives in brief scope some of the most significant changes in fundamental concepts that have resulted from the extraordinary advances made in recent years in the field of experimental physics. These changes have important bearings on nature and life in general as well as on physics. Originally published in 1932. A UNC Press Enduring Edition -- UNC Press Enduring Editions use the latest in digital technology to make available again books from our distinguished backlist that were previously out of print. These editions are published unaltered from the original, and are presented in affordable paperback formats, bringing readers both historical and cultural value.