Ernst Chladni at the understanding of electron orbitals. Since at least 1738, a musical instrument called a "Glasspiel" or "verrillon", created by filling beer glasses with varying amounts of water, was popular in Europe. The beer glasses were struck by wooden mallets shaped like spoons to produce "church and other solemn music". Benjamin Franklin was sufficiently impressed by a verrillon performance on a visit to London in 1757 that he created his own instrument, the glass armonica, in 1762. Franklin's armonica inspired several other instruments, including two created by Chladni. In 1791, Chladni invented the musical instrument called the "euphon" (not to
Social class in 18th-century Spain Social class in 18th-century Spain The social structure of Spain in the 18th century continued to be based upon nobility and peasantry. However, the period also saw the growth of a middle class, centred upon the growing bureaucracy associated with Bourbon rule, and upon a limited development of commerce and industry. In Spain at this period there were a large number of nobles. Some of them were rich while others were poor workers. Although their number decreased during the second half of the century, they continued numerous, due in part to the large number of "hidalgos" in the north of