Principles of natural philosophy, or, A new theory of physics founded on gravitation, and applied in explaining the general properties of matter, the phenomena of chemistry, electricity, galvanism, magnetism, & electro-magnetism This book, "Principles of natural philosophy", by Thomas Exley, is a replication of a book originally published before 1829. It has been restored by human beings, page by page, so that you may enjoy it in a form as close to the original as possible.