I have added the thicknesses for each course and the difference between the N.E. and S.W. readings, both in thickness and in level. It is hoped that these additional entries will give a much clearer picture of how the overseer kept to his levels as each course was laid one upon the other. Understandably, the data raises innumerable questions about method.
Some observations related to the chart appear at the bottom of the page.
We really do not know which is which because Petrie doesn't tell us. As there is only one chance in six that Petrie's NE and SW data reflect the greatest thickness variation for each course most of the entries in the four corner column above will be greater than his. In some cases the total variation for individual courses far exceeds the data given by Petrie, courses 108 and 109 for example. In these two cases the NE and SW thicknesses have been identified as those represented by two bars very close together and greatly separated from at least one other. Course 144 has 5 corner entries marked in.