string or Helmholtz's vortex rings threading through each other. An article about the "Zootrope perfectionné" was published in French scientific magazine Le Cosmos in 1869, but the device was never marketed. Maxwell's original zoetrope and some strips are kept in the collection of the Cavendish Museum in Cambridge. Linear zoetropes A linear zoetrope consists of an opaque linear screen with thin vertical slits in it. Behind each slit is an image, often illuminated. A motion picture is seen by moving past the display. Linear zoetropes have several differences compared to cylindrical zoetropes due to their different geometries. Linear zoetropes can have arbitrarily long animations and can cause images to appear wider than their actual sizes. Subway zoetropes Japan Linear zoetrope-like advertising was in use in Japan in the early 1990s, for example on the line between the Narita airport and central Tokyo. United States In September 1980, independent filmmaker Bill Brand installed a type of linear zoetrope he called the "Masstransiscope" in an unused subway platform at the former Myrtle Avenue station on the New York City Subway. It consists of a wall with 228 slits; behind each slit is a hand-painted panel, and riders of passing trains see a motion picture. After falling into a state of disrepair, the "Masstransiscope" was restored in late 2008. Since then, a variety of artists and advertisers have begun to use subway tunnel walls to produce a zoetrope effect when viewed from moving trains. Joshua Spodek, as an astrophysics graduate student, conceived of and led the development of a class of linear zoetropes that saw the zoetrope's first commercial success in over a century. A display of his design debuted in September 2001 in the Atlanta subway system tunnel and showed an advertisement to riders moving past. The display is internally lit and nearly long, with an animation lasting around 20 seconds. His design soon appeared, both commercially and artistically, in subway systems around North America, Asia, and Europe. In April 2006, the Washington Metro installed advertisement zoetropes between the Metro Center and Gallery Place subway stations. A similar advertisement was installed on the PATH train in New Jersey, between the World Trade Center and Exchange Place stations. At around the same time, the San Francisco Bay Area Rapid Transit (BART) system installed a zoetrope-type advertisement between the Embarcadero and Montgomery stations which could be viewed by commuters traveling in either direction. The