Spirograph a hypocycloid. Spirograph Spirograph is a geometric drawing toy that produces mathematical roulette curves of the variety technically known as hypotrochoids and epitrochoids. It was developed by British engineer Denys Fisher and first sold in 1965. The name has been a registered trademark of Hasbro Inc. since 1998 following purchase of the company that had acquired the Denys Fisher company. The Spirograph brand was relaunched worldwide with original product configurations in 2013 by Kahootz Toys. In 1827 English architect and engineer Peter Hubert Desvignes developed his "Speiragraph", a machine to create elaborate spiral drawings, intended to prevent bank note forgeries.
Denys Ovenden Denys Ovenden Denys Ovenden was born on April 1, 1922. His preoccupation with drawing began very early, since there are drawings on the fly-leaves of books from that period. His natural history interest began. Watercolor is the basic medium for his work, with occasional "gouache" for highlighting or detail. His preferred working surface is a "fashion" type board, "CS2 not surface" being the favorite. Reference sources are most important, and Denys uses a body-live, pinned or pickled, to work from, as pinned and set specimens can be misleading due to shrinkage, discoloration or loss of parts. He does use photographs