AbstractThe determination of aquifer transmissibility by the bail‐test method can be considerably simplified if proper attention is paid to the regular spacing of bailer cycles. The transmissibility calculation will then depend on the evaluation of the difference between two numbers, instead of on the evaluation and summation of a large set of numbers, one number for each bailer cycle. The mathematical development on which this method is based is given briefly and a table listing the sums of the reciprocals of the natural numbers, which is used in the simplified determination, is also presented.The formula for the recovery of the water level after repeated bailing of a well completed in a confined aquifer (Skibitzke, 1958) may be written (Ferris et al., 1962