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��itself felt; weeks must elapse before sufficiently luxuri- ant vegetation has sprung into being so that the courses of the canals can be traced each spring and s u m - mer. And the pe- culiar manner in which the canals seem to creep down from the poles at the rate of two and a half miles an hour lends color to the explanation.

The Groivth and Death of

Vegetation on

Mars This elaborate network of sluices divides the planets into plains of more or less geometrical shape. Blue, green and orange are the colors of these plains — colors that proclaim the char- acter of the areas in question. The blue-green areas are fertile regions fed by the canals ; the orange sections are deserts, hopelessly arid. This distinction Professor Lowell draws by reason of the peculiar fluctuations in hue which the blue-green patches undergo with the ad- vent of spring and winter. As autumn approaches they assume a russet tint, which renders it almost impossible to dis- tinguish them from the orange deserts. When the polar snows begin to melt they gradually deepen in shade until they as- sume the characteristic color of vegeta- tion. Inasmuch as these changes are closely linked with the waxing and wan- ing of the canals, it is evident that the one phenomenon is dependent upon the other.

That the spots toward which the ca- nals converge are the objective points of

���Dr. Percival Lowell, who erected at Flagstaff, Arizona, the finest private ob- servatory in the world for the special study of the planets. Here for many years he has made those observations of Mars which have made him the foremost au- thority on that planet in the world

��Martian irrigation, is demonstrated by the scientific pre- cision with which the canals have been drawn to meet them. Not a soli- tary spot is any- where to be found. Three, four, six, even seventeen ca- n a 1 s concentrate their floods on a single spot. In di- ameter the spots range from seven- ty-five to one hun- d r e d and fifty miles. Like the ca- nals they have been designed with ge- ometrical economy. If there are cities on ]\Iars, it is not unlikely that they are situated in these spots.

Like the canals the spots disappear with the approach of winter; but be- fore they are ex- tinguished the ca- nals have faded away. This is as it should be. Be- fore our time the spots were thought to be lakes and were named accordingly. Professor Lowell regards them as oases studding the Mar- tian deserts. Lakes would never deepen in color; only vegetation can cause the characteristic fluctuations to which the spots are subject.

Are the Canals Real or Merely Illusions f

The amount of ink that has been spill- ed over the canals and their meaning would fill a hogshead. IMany astrono- mers deny that the canals exist at all and regard them as optical illusions produced by eye-strain. But none of these skeptics has had the opportunity of studying Mars night after night in a clear atmos- phere, far from the smoke of cities. Doubting astronomers who have troubled

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