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43 less than a degree wide, or about 30 miles in the narrower instances; in the broader, a little more than a degree, or about 45 miles. Between the two lines, in the cases where the gemination, as it is called, is complete, lies reddish-ochre ground similar to the rest of the surface of the bright regions. Deducting the two half-widths of the bordering canals, we have, therefore, from 120 to 175 miles of clear country between the paralleling lines. The gemination of a canal is a phenomenon individual to the particular canal. Each canal differs from its neighbor not only in the distance the lines lie apart, but in the time at which the duplication occurs. The event seems to depend both upon general seasonal laws governing all the duplications, and upon causes intrinsic to the canal itself. Within limits, each canal doubles at its own good time and after its own fashion. For example, although it seems to be a rule that north and south canals double before east and west eT ere ee Cees bs OO Ae OOS OD MEE. RODS ones, nevertheless, of two north and south lines, one will double, the other will not, synchronously with a doubling running east and west; the same is true of those running at any other inclination. Now this shows that the duplication is not an optical illusion at this end of the line; for, by any double refraction here, all the lines running in the same direction over the disc should be similarly affected, which they are not. On the contrary, there will be, say, two cases of doubling in quite different directions co-existent with several single canals. Nor is there any probability of its being a case of double refraction at the other end of the line,--that is, in the atmosphere of Mars; for in that case it is hard to see why all the lines should not be affected, to say nothing of the fact that, to render such double refraction possible, we must call upon a noumenon to help us out, as we know of no substance capable of the quality upon so huge a scale. Furthermore, what is cogent to the observer, though of no particular weight with his hearers, the phenomenon has no look of double refraction. It looks to be, what it undoubtedly is, a double existence. Strengthening this conclusion is the mode of development of the doubling. This appears to take place in two ways, although it is possible that the two are but different instances of one and the same process. Of the first kind, during this last opposition, the Ganges was an example. The Ganges was in an interesting protoplasmic condition during the whole of last summer. About to multiply by fission, it was not at first evident how this would take place. Hints of gemination were visible when I first looked at it in August. It showed then as a very broad but not dark swath of dusky color, of nearly uniform width from one extremity to the other, with sides suggestively even throughout. It is probable that they were then, as afterward, parallel, and that the slight convergence apparent at the bottom was due simply to foreshortening. The swath ran thus N. N. W. all the way from the Gulf of the Dawn to the Lake of the Moon. By moments of better seeing its two sides showed darker than its middle; that is, it was already double in embryo, with a dusky middle- ground between the twin lines.