These lectures were first given during my tenure of a Walker Ames Visiting Professorship in the Department of Astronautics and Aeronautics at the University of Washington, November 2-12, 1964. I am grateful for the interest shown there and for the tranquil hospitality of Dr. JOHN BOLLARD and Dr. ELLIS DILL, which allowed me the leisure sufficient to write the first manuscript. I thank Dean ROBERT Roy and Dr. GEORGE BENTON for the unusual honor of an invitation to deliver a series of public lectures at my own university. Apart from the footnotes on pp. 49, 50, and 85, which have been added so as to answer questions allowed by the slower pace of silence, and the obviously necessary note on p. 106, the lectures of this second series are here printed as read, February 9-25, 1965. Thus I may call these, in imitation of a famous example, " Bal timore Lectures." Acknowledgment The first lecture is based largely upon my Bingham Medal Address of 1963, part of which it reproduces verbatim. The filth lecture may be regarded as a partial summary of my course on ergodic theory at the International School of Physics, Varenna, 1960. Much of the last lecture runs parallel to my article "The Modern Spirit in Applied Mathematics," ICSU Review of World Science, Volume 6, pp. 195-205 (1964), and some paragraphs are taken from my address to the Fourth U. S. National Congress of Applied Mechanics (1961)."

Providing a comprehensive and up-to-date treatment of observational cosmology, this advanced undergraduate textbook enables students to use quantitative physical methods to understand the Universe. The textbook covers recent developments such as precision cosmology and the concordance cosmological model, inflation, gravitational lensing, the extragalactic far-infrared and X-ray backgrounds, downsizing and baryon wiggles. It also explores the future missions and facilities likely to dominate cosmological research in the future, including radio, X-ray, submillimetre-wave and gravitational wave astronomy. Each chapter contains full-colour figures, worked examples and exercises with complete solutions. Clearly identified key facts and equations help students easily locate important information. Suggestions for further reading provide jumping-off points for students aiming to further their studies. Reflecting decades of Open University experience in undergraduate teaching, this textbook brings students to the forefront of the rapidly developing field of observational cosmology. Accompanying resources to this textbook are available at: http://www.cambridge.org/features/astrophysics.

Orienting us with an insider's tour of our cosmic home, the Milky Way, William Waller and Paul Hodge then take us on a spectacular journey, inviting us to probe the exquisite structures and dynamics of the giant spiral and elliptical galaxies, to witness colliding and erupting galaxies, and to pay our respects to the most powerful galaxies of all-the quasars. A basic guide to the latest news from the cosmic frontier-about the black holes in the centers of galaxies, about the way in which some galaxies cannibalize each other, about the vast distances between galaxies, and about the remarkable new evidence regarding dark energy and the cosmic expansion-this book gives us a firm foundation for exploring the more speculative fringes of our current understanding. This is a heavily revised and completely updated version of Hodge's Galaxies, which won an Association of American Publishers PROSE Award for Best Science Book of the Year in 1986.