As already stated, the temperature at the beginning of combustion is the reading just before the current is turned on, or B in Fig. 25. The point C or the temperature at which combustion is presumably completed, should be taken at a point which falls well within the established final rate of radiation, and not at the maximum temperature that the thermometer indicates in the test, unless it lies on the straight line determining the final radiation. This is due to the fact that in certain instances local conditions will cause the thermometer to read higher than it should during the time that the bomb is transmitting heat to the water rapidly, and at other times the maximum temperature might be lower than that which would be indicated were readings to be taken at intervals of less than one-half minute, _i. e._, the point of maximum temperature will fall below the line determined by the final rate of radiation. With this understanding AB, Fig. 25, represents the time of initial radiation, BC the time of combustion, and CD the time of final radiation. Therefore to apply Pfaundler's correction, formula (19), to the data as represented by Fig. 25. N = 6, R = 0, R' = .01, T = 20.29, T' = 22.83, 20.29 + 22.54 + 22.84 + 22.88 + 22.87 + 22.86 T" = --------------------------------------------- = 22.36 6 _ _ | .01 - 0 | C = 6|0 + -------------(22.36 - 20.29)| |_ 22.85 - 20.29 _| = 6 × .008 = .048 Pfaundler's formula while simple is rather long. Mr. E. H. Peabody has devised a simpler formula with which, under proper conditions, the variation from correction as found by Pfaundler's method is negligible. It was noted throughout an extended series of calorimeter tests that the maximum temperature was reached by the thermometer slightly over one minute after the time of firing. If this period between the time of firing and the maximum temperature reported was exactly one minute, the radiation through this period would equal the radiation per one-half minute _before firing_ plus the radiation per one-half minute _after the maximum temperature is reached_; or, the radiation through the one minute interval would be the average of the radiation per minute before firing and the radiation per minute after the maximum. A plotted chart of temperatures would take the form of a curve of three straight lines (B, C', D) in Fig. 25. Under such conditions, using the notation as in formula (19) the correction would become, 2R + 2R' C = ------- + (N - 2)R', or R + (N - 1)R' (20) 2 This formula may be generalized for conditions where the maximum temperature is reached after a period of more than one minute as follows: