The report summarizes, mainly in a series of diagrams, the results of an investigation of the temperature distribution in a region of Lake Michigan, roughly bounded by Lat. 43 degrees 00' and 43 degrees 30' N, during the period of summer stratification in 1963. Measurements were made with bathythermographs from a railroad ferry vessel and from a research vessel, which was also used, at a mid-lake anchor station, as a platform to measure the vertical distribution of current speed and direction. The measurement program was designed to test the writer's predictions (Mortimer, 1963) that a dominant component of the internal wave pattern, in Lake Michigan in summer and in regions remote from shores, could be described in terms of Poincare waves with characteristic periods close to but always less than the local inertial period (17.5 hr) and with associated currents exhibiting clockwise rotation of the same periodicity and following an elliptical track. The report is prefaced by an illustrated account of internal wave (long wavelengths) and current patterns, associated with Kelvin and Poincare waves, in a rotating, two-layered, rectangular basin of uniform depth and of Great Lakes dimensions. Events observed in Lake Michigan are interpreted in terms of this model. (Author).

"Mortimer chronicles three centuries of inquiry into Lake Michigan from the Native Americans, who called it Michigani (Great Waters), to the French explorers, whose first recorded observations date from the 1600s, to present-day scientists, who use satellite views of the Great Lakes from outer space." "Lake Michigan in Motion is a source of information for amateur naturalists, students, teachers, public officials, a wide variety of scientists and natural resource managers, residents of Lake Michigan's shores, and others who use the lake for their livelihood and recreation."--Jacket.