# Mechanical theory

In science, the mechanical theory, according to 1824 views of French physicist Sadi Carnot, explains the operation of machines which have for a motor the force of men (manpower) or of animals (horsepower), a waterfall (waterpower), an air current (windpower), etc., but not those which receive their motion form heat. [1] In general, the "mechanical theory" is a term that refers to a geometric physics of, pre heat engine period, machines, those such as screw presses, pulleys, water wheels, wind mills, etc., defined by fundamental principles and limits of operation owing to the geometry of movement of the parts and the laws of force.

History
The works of French engineer Lazare Carnot embody the logic of the mechanical theory to a large extent. [2] In particular, Lazare Carnot’s 1778 “Memoir on the Theory of Machines”, written fresh out of engineering school, submitted to the French Academy of Sciences in Paris, in efforts to win their coveted prize contest to formulate a general mechanical theory, acts as a good point representative of the birth of the mechanical theory. Specifically, in an advertisement in the Gazette de France of 18 April 1777, the Academy specified that this machine theory or subject needed to be: [3]

“The theory of simple machines with regard to friction and the stiffness of cordage, [requiring] that the laws of friction and the examination of the effects resulting from stiffness in cordage be determined by new experiments conducted on a large scale; [requiring] further that these experiments be applicable to machines used in the Navy such as the pulley, the capstan, and the inclined plane.”

His two-part entry was titled “Mémoire sur la Théorie des Machines”, part I being his experimental results, part II being the outline of his general theory of machines. [3] A number of more robust publications on the same subject soon followed out, culminating with the 1803 Fundamental Principles of Equilibrium and Movement.

Thermodynamics
The new "mechanical theory of heat", in a sense, can be considered as a formulaic combination:

Mechanical theory of heat (1865) = mechanical theory (1778) + mechanical equivalent of heat (1798) + theory of heat (1837)

developed largely by German physicist Rudolf Clausius between 1850 and 1865, explains the operation of machines which receive their motion from heat, a theory now known as the science of thermodynamics. [4]

References
1. Carnot, Sadi. (1824). “Reflections on the Motive Power of Fire and on Machines Fitted to Develop that Power.” Paris: Chez Bachelier, Libraire, Quai Des Augustins, No. 55.
2. Lazare, Carnot. (1783). Essay on Machines in General, art. 8, trans. Ivor Grattan-Guinness.
3. Gillispie, Charles C. (1971). Lazare Carnot Savant: A Monograph Treating Carnot’s Scientific Work. Princeton University Press.
4. Clausius, R. (1865). The Mechanical Theory of Heat – with its Applications to the Steam Engine and to Physical Properties of Bodies (URL). London: John van Voorst, 1 Paternoster Row. MDCCCLXVII.