Library of Useful Knowledge: Natural philosophy, Volume 31834 |
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Page 8
... earth to verify the conclusions we have already formed respecting the mo- tions of the stars . The earth being con- vex at all points , the horizons of different places , which are always planes touch- ing the earth at those points ...
... earth to verify the conclusions we have already formed respecting the mo- tions of the stars . The earth being con- vex at all points , the horizons of different places , which are always planes touch- ing the earth at those points ...
Page 47
... earth ; and that , with some allowance for local and accidental causes , it does so in nearly the same manner everywhere . The earth there- fore being considered as spherical ( for its variation from an accurately spherical form may ...
... earth ; and that , with some allowance for local and accidental causes , it does so in nearly the same manner everywhere . The earth there- fore being considered as spherical ( for its variation from an accurately spherical form may ...
Page 48
... earth , is necessarily a vertical plane there : the effect of refraction therefore takes place entirely in a ... earth's surface is very small . According to the table given in the treatise on Optics , p . 6 , the ratio of the sine of ...
... earth , is necessarily a vertical plane there : the effect of refraction therefore takes place entirely in a ... earth's surface is very small . According to the table given in the treatise on Optics , p . 6 , the ratio of the sine of ...
Page 57
... earth is a body of large magni- tude ; the distances therefore at which different observers may be placed from each other on its surface may be very great , and the differences between the apparent positions even of very distant bodies ...
... earth is a body of large magni- tude ; the distances therefore at which different observers may be placed from each other on its surface may be very great , and the differences between the apparent positions even of very distant bodies ...
Page 60
... earth is not accurately spherical , the distance TO will not be exactly the same for all places ; nor will the line TO , when produced , necessarily pass exactly through the zenith . All our deductions concerning parallax there- fore ...
... earth is not accurately spherical , the distance TO will not be exactly the same for all places ; nor will the line TO , when produced , necessarily pass exactly through the zenith . All our deductions concerning parallax there- fore ...
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Common terms and phrases
aberration altitude angle apogee apparent diameter appear ascer ascertained astronomers axis calculated called centre circle comet consequently corresponding course declination deduced degree determined direction diurnal motion ecliptic elevation equal equator equinox excentricity fixed stars given greater greatest heavenly bodies heavens Hipparchus horizon hour angle inferior planet instance Jupiter Kepler known latitude latter length less longitude lunar mean anomaly measured meridian method moon moon's nearly node nutation observed orbit parallax parallel passing perigee perihelion period perpendicular planet pole position precession proportion Ptolemy quantity radius refraction remarkable represent respect retrograde motion revolution revolve right ascension rotation round the earth round the sun satellites seen side sidereal sine solar solstice South sphere spherical sun's supposed supposition Surya Siddhanta synodic period tables tance tion triangle true tude variation velocity whole zenith distance
Popular passages
Page 54 - If two triangles have one angle of the one equal to one angle of the other and the sides about these equal angles proportional, the triangles are similar.
Page 18 - ... invisible. These animals are of a great variety of shapes and sizes, and in such prodigious numbers, that, in a short time, the whole surface of the rock appears to be alive and in motion. The most common...
Page 137 - D'Alembert, was the Precession of the equinoxes and the Nutation of the earth's axis, according to the theory of gravitation.
Page 15 - The lowest and most level parts of the earth, when penetrated to a very great depth, exhibit nothing but horizontal strata composed of various substances, and containing almost all of them innumerable marine productions. Similar strata, with the same kind of productions, compose the hills even to a great height. Sometimes the shells are so numerous as to constitute the entire body of the stratum. They are almost...
Page 18 - The examination of a coral reef during the different stages of one tide, is particularly interesting. When the tide has left it for some time it becomes dry, and appears to be a compact rock, exceedingly hard and ragged ; but...
Page 2 - Scotland was divided into two provinces — the one on the north, and the other on...
Page 169 - ... the squares of the periodic times are as the cubes of the distances from the common centre, the centripetal forces will be inversely as the squares of the distances.
Page 3 - ... they pass rapidly along the surface of the sea, and continue a quarter of an hour or more before they disappear. A notion has been entertained that they are very dangerous to shipping, owing to the descent, at the instant of their breaking, of a large body of water sufficient to sink a ship ; but this does not appear to be the case, for the water descends only in the form of heavy rain.
Page 15 - On the barren flank of a rock grows a tree with coriaceous and dry leaves. Its large woody roots can scarcely penetrate into the stone. For several months of the year, not a single shower moistens its foliage. Its branches appear dead and dried; but when the trunk is pierced, there flows from it a sweet and nourishing milk. It is at the rising of the sun that this vegetable fountain is most abundant. The blacks and natives are then seen hastening from all quarters, furnished with large bowls to receive...
Page 3 - Whirlwinds sometimes arisfi from winds blowing among lofty and precipitous mountains, the form of which influences their direction, and occasions gusts to descend with a spiral or whirling motion. They are frequently, however, caused by two winds meeting each other at an angle, and then turning upon a centre. When two winds thus encounter one another, any cloud which happens to be between them is of course condensed and turned rapidly round ; and all substances sufficiently light are carried up into...