First published in 1927 as the second edition of a 1925 original, this book was intended as a general introduction to the principles of thermodynamics for university students involved in the physical sciences. Birtwistle gives a brief overview of the history of science relating to heat and the conservation of energy as well as practical examples to back up salient points in his explanation of key ideas. This book will be of value to anyone with an interest in the history of science.