If one can recall the appearance of forests in the southern and middle part of Maine, say from Bethel or Bangor, fifty years ago, he will remember that from the top of any hill a stretch of dark blue forest was to be seen as far as the eye could reach, and now from the same elevations one can see only an occasional clump of blue forest, while the remaining surface is, according to the season, either bright green, yellow with ripening vegetation, or white with snow, out of which the dark clumps of forest growth are most conspicuous. Considering the contrasting colors in one year covering hundreds of thousands of square miles in various portions of the country, the question naturally arises which of these contrasts would be most conspicuous,--the colors just mentioned of solid land surfaces of vegetation, snow, and desert, or diaphanous clouds with their gray shadows. We are told that Jupiter, with the mean distance at opposition of nearly 400,000,000 miles, shows its clouds, its red spot, and the shadow transits of its satellites. Surely if these conditions are seen from the Earth, the changes in the Earth's appearance above described might be seen from Mars, which at its nearest opposition is only 35,000,000 miles away, and, conversely, any change of similar character in Mars would certainly be visible from the Earth. X COMMENTS AND CRITICISM _Nothing is more difficult and requires more caution than philosophical deduction, nor is there anything more adverse to its accuracy than fixity of opinion._ FARADAY. It will be of interest to examine the writings of certain astronomers, and writers on astronomy, to appreciate the unreasonable conservatism, not to say narrow-mindedness, which color their opinions. It ill becomes students of science to ridicule the honest and persistent labors of such men as Schiaparelli, Lowell, Perrotin, and others, unless they can show an equal devotion to the work. They do not recall the deluge of essays, reviews, and sober treatises which followed Darwin's great work, viewing the evidences of Darwin not thoughtfully, nor based upon any knowledge of the subject, but with contempt, and, in many instances, with vituperation. So rapid, however, was the recognition of Darwin's interpretation of Nature's facts that most of these writers lived long enough to see their protests entirely discredited, or to become enthusiastic advocates of the theory. In their own domain of astronomy these writers are equally forgetful of the earnest and even bitter controversies regarding the demonstration by Chandler of the oscillation of the poles, and consequent variation of latitude, and the final establishment of Chandler's views, in the teeth of opposition, by the greatest astronomers.