162 Proceedings of the Royal Society 
proceeded ro remark that, in order to prevent the condensation 
which would result, we must suppose some resistance to the farther 
approach of the particles, which we may typify by a repulsion ; 
and that these tendencies—the attractive and the repulsive—must 
be in equilibrium. A theory, then, which takes into account only 
one of these equilibrated antagonists, must necessarily be defective. 
And since, in all cases, the attraction supposed to exist between 
two sets of particles must necessarily be resisted by actions between 
them, there can be no tension like that which has been supposed to 
be exhibited by the superficial films of fluids. 
2. Theory of Construction of the Great Pyramid. By John 
Christie, Esq. Communicated by the Bev. W. Lindsay 
Alexander, D.D. 
In his early investigations on the principles of construction of 
the Great Pyramid, the author was forcibly struck with the follow¬ 
ing fact—viz., that if a perpendicular be drawn through the 
apex of the Pyramid to its base, and the unit angle with the hori¬ 
zontal thrown up from the base on each side of this perpendicular, 
the angle comes out on the faces of the Pyramid at the openings 
of the north and south ventilating air-channels; at the same time 
he was led to the conclusion that one-tenth of the base line, and 
the same tenths also applied to the faces of the Pyramid, ruled the 
entire structure. Following this out, and having erected per¬ 
pendiculars on each of these tenths, and horizontals from each 
of the facial divisions, the first step procured a grand central 
point—viz., in the centre of the grand gallery; the next step 
was to account for the position of the King’s Chamber, by the 
intersections of the first and second circles—used in the con¬ 
struction of the Pyramid, as shown in Diagram No. 1. Having 
thus obtained a central perpendicular for the King’s Chamber, he 
then made use of the direction of the celestial equator, and where 
it cut the last-named perpendicular, a third point was gained as a 
centre for the third circle, which completes the Pyramid in its 
external form. He next found, that by connecting the south out¬ 
crop of the air-channel with the north corner of the base, a 
