Includes index.

Formal aspects of method: Exploring the characteristics of a naturally occurring process: Embryology of the chick / Aristotle -- Process of digestion as chemistry / William Beaumont -- Deciding between rival hypotheses: Discovery of dip and the field concept / Robert Norman -- Circulation of sap in plants / Stephen Hales -- Conditions of imprinting / Konrad Lorenz -- Finding the form of a law inductively: Law of Descent / Galileo -- Measurement of the spring of the air / Robert Boyle -- Use of models to simulate otherwise unresearchable processes: Causes of the rainbow / Theodoric of Freibourg -- Exploiting an accident: Preparation of artificial vaccines / Louis Pasteur -- Artificial transmutation of the elements / Ernest Rutherford -- Null results: Impossibility of detecting the motion of the earth / A. A. Michelson and E. W. Morley -- Developing the content of a theory: Finding the hidden mechanism of a known effect: Direct transfer of genetic material / F. Jacob and E. Wollman -- Mechanism of perception / J. J. Gibson -- Existence proofs: Proof of the oxygen hypothesis / A. L. Lavoisier -- Electrolytic isolation of new elements / Humphry Davy -- Discovery of the electron / J. J. Thomson -- Decomposition of an apparently simple phenomenon: Nature of colours / Isaac Newton -- Demonstration of underlying unity within apparent variety: Identity of all forms of electricity / Michael Faraday -- Technique: Accuracy and Care in Manipulation: Perfection of chemical measurement / J. J. Berzelius -- Power and versatility of apparatus: Wave aspect of matter and the third quantum number / Otto Stern -- General bibliography -- Index of names -- Index of subjects.