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Page:Popular Science Monthly Volume 24.djvu/262

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THE POPULAR SCIENCE MONTHLY.

to fifty—days from the end of December to the beginning of February. Among these, sixteen evenings were remarkably favorable, so much so that the greatest magnifying powers could be used.

It was therefore possible, notwithstanding the fact that the apparent diameter of Mars was not over 16" (against 19" in 1877), to obtain results which surpass all previous endeavors. Beginning with the white polar spots, Schiaparelli first mentions that the northern polar spot was always more or less visible. During the months of November and December it appeared separated into several branches or masses, as was also the case in 1879. In the latter half of January these branches began to amalgamate and form a regular, continuous, and uniform calotte, the diameter of which reached about 50° at the beginning of February, and then decreased in a distinctly noticeable manner; while, On the contrary, the southern polar spot remained invisible during the entire period of the observations, even in January and February, when the south pole entered the field of view 2°. From this, in connection with the experience gained in 1879 relative to the visibility of the spot, he concludes that eight months after the southern solstice it had not yet attained a diameter of 20°—a diameter which, according to the observations during the previous opposition, it generally attained to a few weeks before this solstice.

During the course of the observations, various white or whitish spots made their appearance at the southern edge of the planet, greatly resembling the polar spot, but after exact examination and measurement proved to be one or the other of the well-known southern islands of the planet, which appeared white around their edges in consideration of a property peculiar to these localities.

The dark portion (ocean?) which surrounds these islands did not seem to possess this property; and, in order to explain how the polar spot, during the southern winter on Mars, can occupy a part of this locality, it becomes necessary to make the assumption that at such times this part undergoes such changes that it is enabled to appear of a bright white color.

Similar white or whitish spots were observed at intervals at other points of the yellow surface of the planet; some of the better determined points, which had already been noticed in 1877 and 1879, were also visible on this occasion, while others remained invisible. A number of white spots were observed, which, however, were only temporary, particularly in the neighborhood of the northern polar calotte. Emanating from this position, there often would be noticed white inclined stripes passing toward the equator of the planet; the arrangement of these seemed to be dependent upon the rotation of Mars—other positions near the edge of the planet likewise presented a whitish appearance.

A general dimming of the white spots which hid the configuration of the planet was observed on the 18th of January, between