This is the first publication of the two most important notebooks created by William Henry Fox Talbot (1800-1877), the inventor of negative/positive photography. Notebooks P and Q span the period from the first public announcement of photography in 1839 through the 1843 plateau of Talbot's researches. They record both his false starts and his triumphs. While the emphasis is on the new art of photography, there is substantial reference to chemistry, electricity, light, optics, and railroad motive power. The notebook pages are reproduced in full, preserving the tempo and organization of Talbot's thoughts, and keeping his sketches in context. This book will fascinate anyone interested in the history of science or technology.