164 Proceedings of the Royal Society 
angle, which it would not do had its length, breadth, or thickness 
been different, in which case the complement of these blocks would 
have been too large or too small for the coffer content. 
Record of Physical Facts — Water-Levels. 
The King’s Chamber is a noted index of these. That this was 
intended by the Pyramid builder seems to be demonstrated by 
the fact of the rock on which the Pyramid stands having been 
scarped down to the level of the Pyramid’s base, so as to procure 
a horizontal line midway between the external physical fact to 
be recorded, and the internal index of that fact contained in the 
King’s Chamber, serving as it did, at the same time, astronomical 
purposes, neither of which would have held good had the rock not 
been so scarped down. 
These water-levels have been previously indicated by other 
modes than those by which they are now illustrated. It will be 
observed that the circles used to indicate them have also peculiar 
references to other parts of the Pyramid besides those they bear to 
the King’s Chamber. One marked instance may be noted here. 
The circle, which indicates the High Nile-level, touches the floor 
of the King’s Chamber in the centre, and also indicates the angle 
of the floor of the grand gallery. Reference may also be made 
here to one of the circles used in the construction of the chambers 
and passages, it being of a very marked and significant character. 
This circle has its centre in the Pyramid’s base, in the point where 
the “direction of the celestial equator” cuts the base, its radius is 
the prime central point in the centre of the grand gallery, and in 
its course it touches — ls£, The mouth of the entrance passage ; 2 d, 
The step leading down to the Queen’s Chamber ; 3d, The “bottom 
of well” in the lower part of descending passage; 4 th, Rounds 
the Low Nile-level; and 5th, Where it cuts the lower portion of 
the direction of the celestial equator, the High Nile-level. The 
difference between the mean Nile-level and the mean sea-level is 
indicated by an equilateral triangle, the apex of which is in the 
mean sea-level, and the base the mean Nile-level, the length of 
the latter being contained between two perpendiculars — the first 
from the north corner of the Pyramid’s base, the second from the 
first remarkable perpendicular joint in the entrance passage. 
