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. Fig. 21. R.B. Cub. Apex of Cephren above Base Cheops 295·98 Apex of Cheops above Base Cheops 287·77 Apex of Mycerinus above Base Cheops 156·51 Base Cephren above base of Cheops 20·37 Base Mycerinus above base of Cheops 25·37 Piazzi Smyth makes the top of the tenth course of Cheops 414 pyramid inches above the pavement; and 414 divided by 20·2006 equals 20·49 R.B. cubits. But I have already proved that Cheops' 420 cubit base measure occurs at a level of 20·37 cubits above pavement; therefore is this level the level of the top of the tenth course, for the difference is only 0·12 R.B. cubits, or 2½ inches. * * * * * I wish here to note as a matter of interest, but not as affecting my theory, the following measures of Piazzi Smyth, turned into R.B. cubits, viz.:-- PYR. INCHES. R.B. CUBITS. King's Chamber floor, above pavement 1702· = 84·25 Cheops' Base, as before stated 9131·05 = 452·01 King's Chamber, "True Length," 412·132 = 20·40 " " "True First Height," 230·389 = 11·40 " " "True Breadth," 206·066 = 10·20 He makes the present summit platform of Cheops 5445 pyramid inches above pavement. My calculation of 269·80 R.B. cub. (See Fig. 21) is equal to 5450 pyramid inches--this is about 18 cubits below the theoretical apex.