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absorption angle angular appears astronomical atmosphere axis bright lines called carbon cause celestial sphere centre changes chromosphere circle colour comet dark lines density diameter direction disc distance earth earth's orbit ecliptic equator equatorial equinox fixed stars formed Fraunhofer lines gravity heat heavenly bodies hemisphere horizon hydrogen increase iron Jupiter known latitude length lens light longitude lunar magnetic Mars mass mean measured meridian metallic meteorites meteors miles minerals moon moon's motion move nearly nebula needle node northern hemisphere observed orbit parallax parallel particles passing perihelion period photosphere planet point of Aries pole position precession pressure prism produced proper motion radius rays reflected refraction revolution revolving right ascension rocks rotation round the sun satellites seen sidereal sidereal day slit sodium solar spectrum spectra spectroscope spots sun's telescope temperature terrestrial tides tion Uranus vapour velocity Venus vernier vertical winds zenith
Page 239 - Newton generalized the law of attraction into a statement that every particle of matter in the universe attracts every other particle with a force which varies directly as the product of their masses and inversely as the square of the distance between them; and he thence deduced the law of attraction for spherical shells of constant density.
Page 202 - Ascension, and the interval between the departure of any meridian from the mean Sun and its succeeding return to it is the duration of the mean solar day. Clocks and chronometers are adjusted to mean solar time ; so that a complete revolution (through 24 hours) of the hour hand of...
Page 263 - in whatever direction a body moves on the surface of the earth, there is a force arising from the earth's rotation which deflects it to the right in the northern hemisphere, but to the left in the southern.
Page 305 - ... years ago, or we should not have so much as the least observed underground increment of temperature. That is to say, I conclude that Leibnitz's epoch of emergence of the consistentior status was probably between those dates.
Page 132 - Calorie is the amount of heat required to raise the temperature of one kilogram of water one degree Centigrade. It is therefore one thousand times as large as the small calorie. The British Thermal Unit (BTU) is the heat required to raise the temperature of one pound of water one degree Fahrenheit.
Page 133 - The essential principle of the explanation is this ; at some period of time, long past, the sun's initial heat was generated by the collision of pieces of matter gravitationally attracted together from distant space to build up his present mass ; and shrinkage due to cooling gives, through the work done by the mutual gravitation of all parts of the shrinking mass, the vast heat-storage capacity in virtue of which the cooling has been, and continues to be, so slow.
Page 298 - I. All self-luminous bodies in the celestial spaces are composed of meteorites, or masses of meteoritic vapour produced by heat brought about by condensation of meteor-swarms due to gravity. II. The spectra of all bodies depend upon the heat of the meteorites, produced by collisions, and the average space between the meteorites in the swarm, or in the case of consolidated swarms upon the time which has elapsed since complete vaporization.
Page 306 - The process by which this balance is maintained has been called isostasy,80 and the crust is said to be in an isostatic state. The dynamics of the superficial strata with the attendant phenomena of folding and faulting are thus referred to gravitation alone, or to gravitation and whatever opposing force the rigidity of the strata may offer. In a mathematical sense, however, the theory of isostasy is in a less satisfactory state than the theory of contraction. As yet we can see only that isostasy...
Page 202 - As the time deduced from observation of the true Sun is called true or apparent time, so the time deduced from the mean Sun, or indicated by the machines which represent its motion, is denominated mean time.