THE DISCOVERY THAT LIGHT VIBRATES TRANSVERSELY

ARAGO, DOMINIQUE- FRANCOIS et AUGUSTIN FRESNEL. -

Mémoire Sur l'Action que les rayons de lumière polarisés exercent les uns sur les autres.

Paris, Crochard, 1819. 8vo. Contemporary half calf with raised bands and gilt spine. Very light wear along edges. Small stamps on verso of title-page and on verso of plates. In "Annales de Chimie et de Physique", Tome X, 2. Series. 448 pp. a. 2 folded engraved plates. (Entire volume offered). Arago and Fresnel's paper: pp. 288-306.

First appearance of this seminal paper in which Arago and Fresnel described the experiments which demonstrated that light vibrates transversely to its direction of forward movement.

"In a further letter to Arago, dated 29 April 1818 Young recurred to the subject of transverse vibrations, comparing light to the undulations of a cord agitated by one of its extremities. This letter was shown by Arago to Fresnel, who at once saw that it presented the true explanation of the non-interference of beams polarised in perpendicular planes, and that the latter effect could even be made the basis of a proof of the correctness of Young's hypothesis; for if the vibration of each beam be supposed resolved into three components, one along the ray and the other two at right angles to it, it is obvious from the Arago-Fresnel experiment that the components in the direction of the ray must vanish; in other words THAT THE VIBRATIONS WHICH CONSTITUTE LIGHT ARE EXECUTED IN THE WAVE-FRONT." (Edmund Whittaker in "A History of the Theories of Aether and Electricity I", p. 115). - Parkinson, Breakthroughs 1819 P. - Magie "A Source Book in Physics, p. 325 ff.

The volume contains another groundbreaking paper, in which THE CONNECTION BETWEEN ATOMIC WEIGHT AND ATOMIC HEAT WAS ESTABLISHED - THE "LAW OF DULONG AND PETIT".

DULONG, (PIERRE) & (ALEXIS) PETIT. Recherches sur quelques points importans de la théorie de la chaleur. Vol. X, pp. 395-413. (In the volume offered).

"They (Dulang and Petit) were concerned with the specific heats of elements; but if these elements really existed as atoms, it seemed possible that there might be a connection between the weight of the atom and the amount of heat acquired to raise the temperature of a given weight of that element by a certain amount." (DSB). - "One of his (Dulong) most important researches was made in collaboration with Alexis Thérese Petit (1791-1820), with whom he announced the law that the product of atomic weight and specific heat is constant (1819). It rendered a distinct service in fixing atomic weights, especially when these were in question, and enabled Berzelius and later Cannizzaro to arrive at correct atomic weights and the correct number of atoms in molecules." (Leicester & Klickstein, A source Book in Chemistry 1400-1900, p. 273). Magie "A Source Book in Physics", p. 178 ff. - Parkinson, Breakthroughs (1819).

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