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INDEX TO THE PRINCIPIA.
| Æquinoxes, their præcession—the cause of that motion shewn, | 413 | |
| “ | the quantity of that motion computed from the causes, | 458 |
| Air, its density at any height, collected by Prop. XXII, Book II, and its density at the height of one semi-diameter of the earth, shewn, | 489 | |
| “ | its elastic force, what cause it may be attributed to, | 302 |
| “ | its gravity compared with that of water, | 489 |
| “ | its resistance, collected by experiments of pendulums, | 315 |
| “ | the same more accurately by experiments of falling bodies, and a theory, | 355 |
| Angles of contact not all of the same kind, but some infinitely less than others, | 101 | |
| Apsides, their motion shewn, | 172, 173 | |
| Areas which revolving bodies, by radii drawn to the centre of force describe, compared with the times of description, | 103, 105, 106, 195, 200 | |
| As, the mathematical signification of this word defined, | 100 | |
| Attraction of all bodies demonstrated, | 397 | |
| “ | the certainty of this demonstration shewn, | 384 |
| “ | the cause or manner thereof no where defined by the author, | 507 |
| “ | the common centre of gravity of the earth, sun, and all the planets, is at rest, confirmed by Cor. 2, Prop. XIV, Book III, | 401 |
| “ | the common centre of gravity of the earth and moon goes round the orbis magnus, | 402 |
| “ | its distance from the earth and from the moon, | 452 |
| Centre, the common centre of gravity of many bodies does not alter its state of motion or rest by the actions of the bodies among themselves, | 87 | |
| “ | of the forces by which revolving bodies are retained in their orbits, how indicated by the description of areas, | 107 |
| “ | how found by the given velocities of the revolving bodies, | 110 |
| Circle, by what law of centripetal force tending to any given point its circumference may be described, | 108, 111, 114 | |
| Comets, a sort of planets, not meteors, | 465, 486 | |
| “ | higher than the moon, and in the planetary regions, | 460 |
| “ | their distance how collected very nearly by observations, | 461 |
| “ | more of them observed in the hemisphere towards the sun than in the opposite hemisphere; and how this comes to pass, | 464 |
| “ | shine by the sun s light reflected from them, | 464 |
| “ | surrounded with vast atmospheres, | 463, 465 |
| “ | those which come nearest to the sun probably the least, | 495 |
| “ | why they are not comprehended within a zodiac, like the planets, but move differently into all parts of the heavens, | 502 |
| “ | may sometimes fall into the sun, and afford a new supply of fire, | 502 |
| “ | the use of them hinted, | 492 |
| “ | move in conic sections, having their foci in the sun s centre, and by radii drawn to the sun describe areas proportional to the times. Move in ellipses if they come round again in their orbits, but these ellipses will be near to parabolas, | 466 |
| Comet's parabolic trajectory found from three observations given, | 472 | |
| “ | corrected when found, | 495 |
| “ | place in a parabola found to a given time, | 466 |
| “ | velocity compared with the velocity of the planets, | 466 |
| Comets' Tails directed from the sun, | 489 | |
| “ “ | brightest and largest immediately after their passage through the neighbourhood of the sun, | 487 |
| “ “ | their wonderful rarity, | 490 |
| “ “ | their origin and nature, | 463 |
| “ “ | in what space of time they ascend from their heads, | 490 |
