Library of Useful Knowledge: Natural philosophy, Volume 31834 |
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Page 8
... known , and go by the name of the poles of the hea vens . They are points , as we have already seen , in the meridian of every place , and therefore they no where ap- pear either in the East or West side of the heavens ; if however we ...
... known , and go by the name of the poles of the hea vens . They are points , as we have already seen , in the meridian of every place , and therefore they no where ap- pear either in the East or West side of the heavens ; if however we ...
Page 31
... known period , its mean place at a known time , the mean time of the occurrence of a given event , are easily found ; for the intervals of the mean time , and the rate of the mean motion being always the same , we only want to know how ...
... known period , its mean place at a known time , the mean time of the occurrence of a given event , are easily found ; for the intervals of the mean time , and the rate of the mean motion being always the same , we only want to know how ...
Page 46
... known . Conversely , if the declination , or North polar dis- tance of the body be known , and its alti- tude when on the meridian of any place observed , the elevation , or zenith dis- tance , of the Pole there may be ascer- tained ...
... known . Conversely , if the declination , or North polar dis- tance of the body be known , and its alti- tude when on the meridian of any place observed , the elevation , or zenith dis- tance , of the Pole there may be ascer- tained ...
Page 67
... known by the name of fixed stars . It is not necessary here to detail all the precautions necessary in observing these variations ; they are very small in amount , the greatest known not being more than 4 " in the course of a year , and ...
... known by the name of fixed stars . It is not necessary here to detail all the precautions necessary in observing these variations ; they are very small in amount , the greatest known not being more than 4 " in the course of a year , and ...
Page 69
... known , the other may be computed : for P , the length of the year , is known . The angular motions however both of the sun and moon are variable , and this method therefore seems to give but an inaccurate mode of estimating the ...
... known , the other may be computed : for P , the length of the year , is known . The angular motions however both of the sun and moon are variable , and this method therefore seems to give but an inaccurate mode of estimating the ...
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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...