he fragmentary curves are steep and receding far from
the equator; or whether they are flat and lying close along the
equator; whether they span less or more than 180 degrees; the
curves determined on the supposition that they are the work of
satellites revolving round Mars agree with the mapped curves;
following them with wonderful accuracy; possessing their
properties, and, indeed, in some cases, actually coinciding with
them.

I may add that the inadmissible span of 180 degrees and spans
very near this value, which are not well admissible, are so far
as I can find, absent. The curves are not great circles.

You will require of me that I should explain the centres of
radiation so conspicuous here and there on Lowell's map. The
meeting of more than two lines at the oases is a phenomenon
possibly of the same nature and also requiring explanation.

In the first place the curves to which I have but briefly
referred actually give rise in most cases to nodal, or crossing
points; sometimes on the equator, sometimes off the equator;
through which the path of the satellite returns again and again.
These nodal points will not, however, afford a general
explanation of the many-branched radiants.

It is probable that we should refer such an appearance

193

as is shown at the Sinus Titanum to the perturbations of the
satellite's path due to the surface features on Mars. Observe
that the principal radiants are situated upon the boundary of the
dark regions or at the oases. Higher surface levels may be
involved in both cases. Some marked difference in topography must
characterise both these features. The latter may possibly
originate in the destruction of satellites. Or again, they may
arise in crustal disturbance of a volcanic nature, primarily
induced or localised by the crossing of two canals. Whatever the
origin of these features it is only necessary to assume that they
represent elevated features of some magnitude to explain the
multiplication of crossing lines. We must here recall what
observers say of the multiplicity of the canals. According to
Lowell, "What their number maybe lies quite beyond the
possibility of count at present; for the better our own air, the
more of them are visible."

Such innumerable canals are just what the present theory
requires. An in-falling satellite will, in the course of the last
60 or 80 years of its career, circulate some 100,000 times over
Mars' surface. Now what will determine