The improvements and additions embodied in the new London edition are fully enumerated in the Author’s Preface. The American publishers have supplied what was much needed, a complete Glossary of Scientific and Technical Terms; which, with some few additions scattered through the pages, and enclosed in brackets [ ], were prepared by Dr. Ruschenberger.

These additions, while they have improved the work, have added materially to the number and size of the pages. The publishers, consequently, trust that it will be found more effectually suited to the wants of the private reader as well as to those of the higher classes in schools.

Philadelphia, December, 1849.