Library of Useful Knowledge: Natural philosophy, Τόμος 31834 |
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Σελίδα 23
... extreme variations produce a difference of more than about one - fifteenth . The main causes of the different warmth of the seasons are to be found in the different lengths of the time during which he is above the horizon , and the ...
... extreme variations produce a difference of more than about one - fifteenth . The main causes of the different warmth of the seasons are to be found in the different lengths of the time during which he is above the horizon , and the ...
Σελίδα 29
... extreme power at different places , his average power may be accurately com- pared . The whole time for which the sun in the course of a year is above the horizon , is everywhere the same or nearly so . If , in fig . 5 , eq be a circle ...
... extreme power at different places , his average power may be accurately com- pared . The whole time for which the sun in the course of a year is above the horizon , is everywhere the same or nearly so . If , in fig . 5 , eq be a circle ...
Σελίδα 30
... extreme cold , and the countries near the equi- noctial to be equally so from extreme heat . The experience of modern times has proved that both suppositions were extravagant : and it has farther shewn that the heat of different places ...
... extreme cold , and the countries near the equi- noctial to be equally so from extreme heat . The experience of modern times has proved that both suppositions were extravagant : and it has farther shewn that the heat of different places ...
Σελίδα 44
... extreme accuracy is hardly ne- cessary in a matter which , after all , is more of popular than scientific import- ance . An error of less than a day in 4000 years cannot derange the ordinary calculations of time ; and astronomers , in ...
... extreme accuracy is hardly ne- cessary in a matter which , after all , is more of popular than scientific import- ance . An error of less than a day in 4000 years cannot derange the ordinary calculations of time ; and astronomers , in ...
Σελίδα 49
... extreme stratum R , R2 , the results there will be exactly the same as those previously deduced for a single stratum of uniform density , for it is one ; and then we have al- ready seen that the deflection at R2 will be less than if the ...
... extreme stratum R , R2 , the results there will be exactly the same as those previously deduced for a single stratum of uniform density , for it is one ; and then we have al- ready seen that the deflection at R2 will be less than if the ...
Άλλες εκδόσεις - Προβολή όλων
Συχνά εμφανιζόμενοι όροι και φράσεις
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
Δημοφιλή αποσπάσματα
Σελίδα 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.
Σελίδα 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...
Σελίδα 137 - D'Alembert, was the Precession of the equinoxes and the Nutation of the earth's axis, according to the theory of gravitation.
Σελίδα 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...
Σελίδα 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...
Σελίδα 2 - Scotland was divided into two provinces — the one on the north, and the other on...
Σελίδα 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.
Σελίδα 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.
Σελίδα 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...
Σελίδα 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...