He showed also that each particle of a crystal {183} that exhibits pyro-electricity is itself a source of the same sort of electricity and exhibits polarity. His experimental observations served to prove also that the pyro-electric state has an important connexion with the want of symmetry in the crystals of the substances that exhibit this curious property. In tourmaline, for instance, he found the vitreous charge always at the summit of the crystal which had six faces, and the resinous electricity at the summit of the crystal with three faces. His experiments soon showed him, too, that there were a number of other substances, besides tourmaline, which possessed this same electrical property when subjected to heat in the crystalline stage. Among these were the Siberian and Brazilian topaz, borate of magnesia, mesotype, sphene, and calamine. In all of these other pyro-electrical crystals, Haüy detected a corresponding deviation from the rules of symmetry in their secondary crystals to that which occurs in tourmaline. In a word, after he had concluded his experiments and observations there was very little left for others to add to this branch of science, although such distinguished men as Sir David Brewster in England were among his successors in the study of the peculiar phenomena of pyro-electricity. It may naturally enough be thought that, born in the country, of poor parents, and compelled to work for his living, Haüy would at least have the advantage of rugged health to help him in his {184} career. He had been a delicate child, however; and his physical condition never improved to such an extent as to inure him to hardships of any kind. One of his biographers has gone so far as to say that his life was one long malady. The only distraction from his almost constant suffering was his studies. Yet this man lived to be nearly eighty years of age, and accomplished an amount of work that might well be envied even by the hardiest. In the midst of his magnificent success as a scientist, Haüy was faithful to all his obligations as a priest. His name was known throughout Europe, and many of the scientific societies had considered that they were honoring themselves by conferring titles, or degrees, upon him; but he continued to be the humble, simple student that he had always been.