1903.] LOWELL—THE CARTOUCHES OF MARS. 30a 
THE CARTOUCHES OF MARS. 
BY PERCIVAL LOWELL. e 
(Read December 4, 1903.) 
That changes take place upon the surface of Mars is manifest to 
anyone who has given the planet prolonged study. Not only do 
the polar caps wax and wane with regular rhythm, but the dark 
markings with which the disk is diversified deepen in tone or fade 
away as the months succeed each other. The phenomena known 
as the ‘‘canals’’ are likewise subject to transformation. At times 
they are conspicuous; at times invisible. And what is yet more 
striking, each canal has its own times and seasons, its exits and its 
entrances. What dates the one does not date its neighbor; and 
still less its antipodes. The Ganges will be seen when the Titan is 
invisible and the Titan. be evident when the Ganges can scarcely 
be made out. 
Particular ‘‘ canals’’ are not sole instances of such change. 
On occasion ‘‘canals’’ in whole regions appear to be blotted out. 
The most careful scrutiny fails to detect them, though distance be 
at its minimum and definition at its best. Yet before or after, 
under conditions much less favorable, the region stands out peopled 
with lines. Even the strongest and best known of these strange 
pencilings seem at certain seasons but wan ghosts of their usual 
selves. As for their more tenuous companions, it almost taxes faith 
to believe that they can ever have existed at all. 
In order to discover what, if any, law underlay these shifting 
phenomena, I bethought me some two years ago of deducing from 
my drawings the percentage of visibility of given markings at in- 
tervals during an opposition, and of then collating the results. The 
great number of drawings at my disposal at once suggested this 
method and increased its trustworthiness, since the accuracy of a 
percentage heightens with the number that go to make it up. 
To get the percentage I had recourse to the following plan. 
Taking the mean longitude of the marking from the map, I 
considered all the drawings which, from the longitude of their 
centres, might be expected to show the marking within certain 
zones from the central meridian, and then noted the appearance or 
non-appearance in each of the marking in question. Three such 
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