PREFACE. Often while plotting the adiabatic curve on an indicator card taken from an ammonia compressor, I have wished to shorten the time required and simplify the process. This led to working out the constants in Table No. l. Having these constants, Table No. 2 naturally suggested itself to still further simplify the work. In addition to this I have added such other matter as seemed pertinent to a work of this character, hoping to place before the reader all necessary references for one who may have to work up indicator cards taken from an ammonia compressor. If my reader appreciates the value of the adiabatic curve after looking through this work, and learns to use Table No. 2, I feel that my aim will have hit the mark....