besides the 'seas' of various sizes there were numerous very small black
spots apparently quite circular and occurring at every intersection or
starting-point of the 'canals.' Many of these had been seen by
Schiaparelli as larger and ill-defined dark patches, and were termed
seas or lakes; but Mr. Pickering's observatory was at Arequipa in Peru,
about 8000 feet above the sea, and with such perfect atmospheric
conditions as were, in his opinion, equal to a doubling of telescopic
aperture. They were soon detected by other observers, especially by Mr.
Lowell in 1894, who thus wrote of them:

"Scattered over the orange-ochre groundwork of the continental regions
of the planet, are any number of dark round spots. How many there may be
it is not possible to state, as the better the seeing, the more of them
there seem to be. In spite, however, of their great number, there is no
instance of one unconnected with a canal. What is more, there is
apparently none that does not lie at the junction of several canals.
Reversely, all the junctions appear to be provided with spots. Plotted
upon a globe they and their connecting canals make a most curious
network over all the orange-ochre equatorial parts of the planet, a mass
of lines and knots, the one marking being as omnipresent as the other."

_Changes of Colour recognised._

During the oppositions of 1892 and 1894 it was fully recognised that a
regular course of change occurred dependent upon the succession of the
seasons, as had been first suggested by Schiaparelli. As the polar snows
melt the adjacent seas appear to overflow and spread out as far as the
tropics, and are often seen to assume a distinctly green colour. These
remarkable changes and the extraordinary phenomena of perfect straight
lines crossing each other over a large portion of the planet's surface,