Introduction A VIGNETTE* of the stages of development of inertial navigation at the M.I.T. Instrumentation Laboratory has been provided by the author. An earlier work provides a tutorial reference on the basic principles of the instruments and systems that were developed. Because this technology grew largely from classified programs, publication of the description of the technology for specific systems has often lagged by a decade or more, and sometimes has lacked coverage altogether. Also because of the author's responsibility for these classified programs, he was often constrained from publishing until after someone less intimately involved had already disclosed information on the programs of inertial navigation. Even at this late date, a description of the Mark 14 "Draper Sight" has not appeared in the open literature. It is the purpose of this treatise to describe some of the major systems that contributed to the evolution of inertial navigation, and to provide a record of the performance of some of these historically significant programs. An underlying theme is the continuity of gyroscopic sensor technology from the fire control systems of the Mark 14 vintage to the first successful inertial navigators. It is shown how the single degree of freedom gyroscopic element was adapted to perform simultaneously both the sensing and computation requirements for solving the fire control problem associated with close-in attacking aircraft. Refinements made to this gyroscopic element, including precise control of torques applied to the output gimbal, and eventual flotation led to the sensor technology that was eventually adapted to solving the inertial navigation problem.