First edition of the author’s first publication.

“Haüy is often called the founder of crystallography, and the law of rational indices still bears his name. In this work he showed how the structure of a crystal could be accounted for by the various geometrical arrangements of its integrant molecules in three dimensions. He not only explained using geometrical principles the six basic forms of crystals; he also explained the phenomena of twinning, pseudomorphism, etc. The Essai is the first truly scientific treatise on crystallography, and Haüy’s mathematical explanations of the structure of crystals greatly assisted in the discovery and classification of new minerals” (Neville).

René Just Haüy (1743-1822), “founder of the science of crystallography, [this work] enunciated ‘Haüy’s law of rational indices’ of the faces of crystals” (Horblit).

“In 1784 [Haüy] published Essai d’une théorie sur la structure des cristaux which laid the foundation of the mathematical theory of crystal structure” (DSB).

Some occasional foxing, binding expertly restored.