Bridges I have crossed

In this paper, types of electrical measurement apparatus based on bridge circuits are discussed. Instruments based on Wheatstone´s bridge such as Christie´s bridge, Leeds & Northrup Wheatstone bridges, Kelvin bridge and General Radio AC bridges are discussed. These instruments range from the most basic to ones with many enhancements. All of the bridges described and illustrated were donated by various American college and university physics departments. These tools offer a history of the quickly developing field of electrical measurement in the late 19th and early 20th Centuries.