By the 1760s (or earlier) German artisans had invented a so-called "pulse hammer" (Pulshammer). In 1767 Benjamin Franklin visited Germany, saw a pulse hammer, and in 1768, improved it. Franklin's pulse hammer consisted of two glass bulbs connected by a U-shaped tube; one of the bulbs was partially filled with water in equilibrium with its vapor. Holding the partially filled bulb in one's hand would cause the water to flow into the empty bulb. In 1872, the Italian physicist and engineer Enrico Bernardi combined three Franklin tubes to build a simple heat motor that was powered by evaporation in a way similar to the drinking bird.