John James Wild made the bases of Cheops, Cephren, and Mycerinus, respectively, 80, 100, and 104·90 cubits above some point that he called Nile Level.
His cubit was, I believe, the Memphis, or Nilometric cubit—but at any rate, he made the base of Cephren 412 of them.
I therefore divided the recognized base of Cephren—viz., 707·75 British feet—by 412, and got a result of 1·7178 British feet for his cubit. Therefore, his measures multiplied by 1·7178 and divided by 1·685 will turn his cubits into R.B. cubits.
I thus make Cheops, Cephren, and Mycerinus, respectively, 81·56, 101·93, and 106·93 R.B. cubits above the datum that J. J. Wild calls Nile Level. According to Bonwick's "Facts and Fancies," p. 31, high water Nile would be 138½ ft. below base of Cheops (or 82·19 R.B. cubits).
Piazzi Smyth makes the pavement of Cheops 1752 British inches (or 86·64 R.B. cubits) above average Nile Level, but, by scaling his map, his high Nile Level appears to agree nearly with Wild.
It is the relative levels of the Pyramids, however, that I require, no matter how much above Nile Level.
Cephren's base of 420 cubits being 101·93 cubits, and Cheops' base of 452 cubits being 81·56 cubits above Wild's datum, the difference in level of their bases is, 20·37 cubits.
The ratio of base to altitude of Cheops being 330 to 210, therefore 20·37 cubits divided by 210 and multiplied by 330 equals 32 cubits; and 452 cubits minus 32 cubits, equals 420.
Similarly, the base of Mycerinus is 5 cubits above the base of Cephren, and the ratio of base to altitude 32 to 20; therefore, 5 cubits divided by 20 and multiplied by 32 equals 8 cubits to be added to the 210 cubit base of Mycerinus, making it 218 cubits in breadth at the level of Cephren's base.
Thus, a horizontal section or plan at the level of Cephren's base would meet the slopes of the Pyramids so that they would on plan appear as squares with sides equal to 218, 420, and 420 R.B. cubits, for Mycerinus, Cephren, and Cheops, respectively.