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The economy grew and government did not grow , and government went down a little as a fraction of income . Beginning in 1565 , when Swiss physician Conrad Gesner of Zurich first described a pencil as a writing rod held in a wooden case , the pencil underwent a slow development eraser on the end , paint to forestall splinters , flat sides to retard rolling that hit a plateau more than a century ago . It uses a diagram as a heuristic to guide the theorem prover 's search , eliminating subgoals when not satisfied by the diagram . Due to modern equipment and tools , it is currently experiencing a revival as a versatile medium in the contemporary art world .