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according already appearance astronomers atmosphere axis bodies brightness called cause celestial centre clouds colour comets compared considerable constellation continuous dark described diameter dimensions direction disappear disk distance distinguished Earth eclipse entire equal equator existence extends extreme fact follows give given globe greater heat heavens hemisphere Herschel horizon idea increase intensity Jupiter known laws length less light luminous lunar magnitude Mars mass mean measure Mercury miles Milky Moon move movement naked eye nature nearly nebulć night observed occupy orbit pass period phenomena physical planet poles portion position present rays regions relative remains remarkable represented ring rise rotation round satellites Saturn seasons seen separated side situated solar sometimes southern space stars surface surrounded telescope terrestrial varies various Venus visible zone
Síđa 86 - Astronomers, with a view of obtaining a convenient and uniform measure of time, have recourse to a mean solar day, the length of which is equal to the mean or average of all the apparent solar days in a year. An imaginary Sun, called the mean Sun...
Síđa 174 - It follows that in the course of a year Mars presents its various regions to the Sun, nearly like our globe, so that the length of the days and the nights, in the different latitudes, is distributed in the same manner. The extreme zones, tomd and frigid, are a little more extended, proportionally, which consequently reduces the surface of the temperate zones.
Síđa 223 - We see it as Columbus saw America from the shores of Spain. Its movements have been felt, trembling along the far-reaching line of our analysis, with a certainty hardly inferior to that of ocular demonstration.
Síđa 162 - ... the most remote condition, of which we have positive evidence, was that of small, detached, melted globules, the formation of which cannot be explained in a satisfactory manner, except by supposing that their constituents were originally in the state of vapour, as they now exist in the atmosphere of the Sun ; and, on the temperature becoming lower, condensed into these
Síđa 131 - Beyond the second ridge a talus slopes gradually down north ward» to the general level of the lunar surface, the whole presenting an appearance reminding the observer of the concentric moraines of the Rhone glacier. These ridges are visible for the whole period during which that portion of the moon's surface is illuminated, but it is only about the third day after the first quarter and at the corresponding phase of the waning moon (when the sun's rays falling nearly horizontally, throw the details...
Síđa 131 - ... and streaks of the lunar surface, are not improbably due to former glacial action. Notwithstanding the excellent definition of modern telescopes, it could not be expected that other than the most gigantic of the characteristic details of an ancient glacier bed would be rendered visible.
Síđa 176 - D' Arrest, deduced from this circumstance the evident proof of a common origin. ' One fact,' he says, ' seems above all to confirm the idea of an intimate relation between all the minor planets ; it is, that, if their orbits are figured under the form of material rings, these rings will be found so entangled, that it would be possible, by means of one among them taken at hazard, to lift up all the rest.
Síđa 42 - ... the observation commenced, about half-past eleven on the date given, the tongue of facula was extremely brilliant ; by one o'clock, it had become apparently less brilliant than any portion of the penumbra. At the same time it seemed to be ' giving out,' at its end, and a portion of the umbra between it and the penumbra appeared to be veiled with a stratus cloud evolved out of it. After a time, condensation seemed going on on the following portion of the cloudy mass. So that a very brilliant mass...
Síđa 153 - ... the phases of the eclipse are reproduced in an inverse order, until the entire emersion of the Moon. The Moon, therefore, does not always completely disappear in total eclipses. The cause of this fact lies in the refraction of the solar rays in traversing the lower strata of the Earth's atmosphere ; they are diverted, and purple our Moon with the tints of sunset. It sometimes happens, however, that the Moon becomes quite invisible during a total eclipse ; as examples of this we may quote the...