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vapour-ocean constitutes an intermediate state of matter in 
unstable equilibrium with other states at all surfaces of 
contact. By interactions arising thereout, the simple static 
conditions of force existing prior to land-upheaval are now, 
in the view of the Author, partly replaced by more complex 
phases of force ; and thus light, heat, electricity, and magnet- 
ism, which are expressions of these complex phases, have 
their root in local reactions between unstable states of terres- 
trial matter at surfaces of abnormal contact when under the 
tension of cosmical force — -just as all these “imponderable 
elements” are evoked in the voltaic battery by surface, 
reaction of dissimilar solids and liquids in presence of atmo- 
spheric tension. In short, the ceaseless molecular changes 
and local motions of terrestrial matter would, on this 
hypothesis, be mainly referred to the differential action 
arising out of land-upheaval. 
Recurring to the “ wave of high water” which formed the 
special subject of the Paper, another phase of the present 
residual of that differential action would give rise to the tidal 
motions of ocean surfaces, the perturbative action centering 
on land areas, and attaining a maximum value on the shores 
of those areas. By discussing the hours of high water at 
full and change for the principal places of the globe, given 
in the Admiralty Tide Tables for 1863 (the data being first 
reduced to Greenwich mean time), the author arrived at the fol- 
lowing law of the progression of the wave of high water : — 
In all land areas in the northern hemisphere the leave of 
high water tends to revolve round the coast in the direction of 
the hands of a watch, and in like areas in the southern 
hemisphere against the hands of a watch. 
Theoretically, this law should hold good in proportion as 
land areas approximate to the circular form, with wide 
uninterrupted ocean spaces all round. In a perfectly circular- 
area of this kind, the differential action would have points 
of maximum and minimum effect on opposite shores at every 
