models, insects and other objects, instead of pictures, with perfect success." The horizontal slits (like in Czermak's Stereophoroskop) allowed a much improved view, with both eyes, of the opposite pictures. William Ensign Lincoln & Milton Bradley's Zoetrope (1865–1867) William Ensign Lincoln invented the definitive zoetrope in 1865 when he was about 18 years old and a sophomore at Brown University, Providence, Rhode Island. Lincoln's patented version had the viewing slits on a level above the pictures, which allowed the use of easily replaceable strips of images. It also had an illustrated paper disc on the base, which was not always exploited on the commercially produced versions. On advice of a local bookstore owner, Lincoln sent a model to color lithographers and board game manufacturers Milton Bradley and Co. Some shop owners advertised the zoetrope in American newspapers in December 1866. William E. Lincoln applied for a U.S. patent for his Zoëtrope on July 27, 1866 as an assignor to Milton Bradley, and it was granted on April 23, 1867. It was also patented in the U.K. on June 7, 1867 (application March 6, 1867) under no. 629, by Henry Watson Hallett (as a communication to him by Milton Bradley), and in France by Charles William May (filed May 14, 1867). Over the years Milton Bradley released at least seven numbered series of twelve zoetrope strips each, as well as a set of twelve strips by Professor Robert Hallowell Richards showing the gradual transformations from one isometric form to another, and one separately available strip showing the progress of the Grecian bend (a woman morphing into a camel). The London Stereoscopic & Photographic Company was licensed as the British publisher and repeated most of the Milton Bradley animations, while adding a set of twelve animations by famous British illustrator George Cruikshank in 1870. French licensee F. Delacour & Bakes produced the "Zootrope, ou cercle magique", of which newspaper Le Figaro ordered 10,000 copies to sell to subscribers at a reduced price. James Clerk Maxwell's improved zoetrope In 1868 James Clerk Maxwell had an improved zoetrope constructed. Instead of slits it used concave lenses with a focal length equaling the diameter of the cylinder. The virtual image was thus seen in the centre and appeared much more sharp and steady than in the original zoetrope. Maxwell drew several strips that mostly demonstrated subjects relating to physics, like the vibrations of a harp