The theoretical and observed values thus agree within the limit of error in the measurements. The theoretical curve is shown in Curve A, Fig. 80 (with the observed points marked, for comparison). The curve B shows the theoretical curve of the decay of the activity of Th X and the emanation, supposing there is no further change into the active deposit. Curve C shows the difference curve between the curves A and B, i.e. the proportion of the activity at different times due to the active deposit. The activity due to the latter thus rises to a