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 the École Polytechnique. Much to his credit, the greatest military genius the world has ever seen was always interested in the work of men of science, and greatly esteemed their talents. It was through the influence of Napoleon (then First Consul) that Alexander Volta was awarded a gold medal, a prize of 6000 francs (both of the Académie des Sciences), and the Cross of the Légion d'Honneur, for his electrical researches.

In the year (1809) that Napoleon defeated the Austrians at Wagram, and annexed Tuscany and the Papal States, Gay-Lussac announced his discovery of the law of volume. This all-important law is generally stated, in these days, in the following words: When gases or vapours, either elementary or compound, unite together to form a new product, the resulting product always occupies two volumes. Occasionally the resulting volume is the sum of the constituent volumes, but usually there is condensation. The following examples illustrate the law of Gay-Lussac:—

The resulting volume is always two.