18. The Water of Rivers contains many Particles of different Metals, Minerals, Sands, oleaginous and other Substances; as alfo certain fubtile Spirits of Vitriol, Salt, Sulphur, &c.

19.

The Rivers that have Gold-Sand enumerated. 20. The Waters of most Rivers differ in Colour, Gravity, and other Qualities.

21. Certain Rivers are fo inlarged, at stated Times, as to overflow their Banks.

22. To enumerate thefe Rivers, and their Caufes. 23. To explain the Origin and Rife of Springs. 24. To find whether a Spring, or Well, may be made in a Place affigned.

25. To make a Well in a given Spot; if the Thing be poffible.

26. To make an apparent Spring in a Place affigned; if the Thing be poffible.

27. To bring a River from a Spring, or from another River, to a given Place, if the Thing be possible. 28. The Art of Levelling, or taking the Fall of Water, &c.

29. The great Rivers of a long Course enumerated. 30. Certain Rivers have Whirlpools and Swallows. 31. River-Water lighter than Sea-Water.

CHA P. XVII.

Of Mineral-Waters, Hot-Springs, &c. Page 359 1. No Water found pure and elementary.

2. Mineral Waters defined.

3. Three general Kinds of Mineral Waters.

4. To explain the Origin of Mineral Waters.

5. That the particular Species of Mineral Waters are infinite.

6. To enumerate the more remarkable and extraordinary Differences of Waters.

7. Of the Acidulæ, or tart Waters,

8. Of Hot Springs.

9. Of oily and unctuous Waters. 10. Of bitter Waters.

11. Of extreamly cold Springs.

12. Of fuch Waters as tranfmute or alter Substances. 13. Of poisonous and Mortal Waters.

14. Of coloured Waters.

15. Of Salt-Waters.

16. Of bubbling, or boiling, Springs, and such as break forth with a violent Spirit.

17. Springs that run only at stated Times.

CHA P. XVIII.

Of the Change, and Origin of dry Parts and watery, on the Earth.

Page 395 1. To examine the extant Surface of the Earth, and that covered with Water.

2. The Surface of the Land and Water not perpetually the fame.

3. To compute how much Sand, and how much Water the Earth contains.

4. Waters for fake the Shores, and leave them dry on many Accounts; and first, as in Mears and Bogs. 5. Rivers forfake their Banks and Chanels, and afford new Land.

6. Lakes are dried up, and changed to Land. 7. Streights are dried up.

8 Bays are dried up.

9. Parts of the Ocean are dried up.

10. To explain the Origin of Sand-Banks.

11. Whether Sand-Banks may become a part of the neighbouring Continent.

12. Ilands are formed feveral Ways.

13. The more extraordinary Ways wherein Islands are formed.

14. Of Floating Islands.

15. Rivers change their Chanels many Ways, or run over new Traits of Land.

6. Lakes

16. Lakes, Meers, and Bogs poffefs Spaces of Land they did not occupy before.

17. The Ocean poffeffes new Tracts of Land, where it did not appear before.

18. Whether the entire Surface of the Earth may be folely poffeffed by Water alone, or Land alone. 19. Why there are few Iflands in the middle of the Ocean; but many Shoals of them near Continents, or larger Islands.

20. Why Lands prove fertile or barren; and why on the Sea-Shore the kind of Earth alters that covers the Fields.

CHA P. XIX.

Of the Air and Atmosphere.

Page 419

1. Exhalations continually rife from the Parts of

the Earth.

2. The State of the Atmosphere.

3. Exhalations are thicker or thinner at different Times, and in different Places.

4. Various Kinds of Exhalations.

5. The Particles of the Air reflect the Sun's Rays, like a Speculum.

6. The upper Parts of the Atmosphere are more rarified than the lower.

7. Exhalations are driven upwards by a violent Motion; tho' their natural Tendency is downwards. 8. The Atmosphere when warmed poffeffes a larger Space, and when cold a lefs.

9. To make a Thermometer, or Weather-Glass. 10. How, or to what Degree, the Air may be rarified. 11. Why the Air is generally thick and Cloudy in the Frigid Zone.

12. Why the Air is thin and clear in violently frosty Weather.

13. Why the Air appears thicker at the Horizon. 14. Whether the Air, or Atmosphere, be of the fame Height in all Places.

15. The

15. The Condenfation and Rarifaction of the Air does not alter it's Height.

16. The Height of the Air the fame at all Times, and in all Places.

17. The Atr more condenfed in the Winter, and at Night, than in the Summer, and by Day.

18. The different Denfity of the Air in different Places. 19. The middle Region of the Air nearer the Earth in Places contiguous to the Pole.

20. In Places adjacent to the Pole the hot Region of the Air, or the beginning of the upper Region,

is more remote.

21. The Rays of the Sun, Moon, and Stars are refracted in the Air.

22. On Account of this Refraction the Sun and Moon appear to rife fooner than they ought.

23. The thicker the Air, the greater the Refraction. 24. The thicker the Air, the fooner the Sun and Moon appear to rife.

25. The lower the Air that causes the Refraction, the fooner the Stars appear to rife.

26. The Refraction of a Star may be the fame in the fame Situation, tho' the Height of the Air be different. 27. If the Air be thicker, or lower, in one Place than in another, the Sun or Moon will appear fooner in the former than in the latter.

28. If the Air be thicker and higher in one Place than another, the Stars will accordingly be seen to rife Sooner, or later.

29. Two Refractions being taken at two Altitudes, to find from thence both the Height and Thickness of the Air, with Respect to the Ether, or the Law of Refraction.

80. To find the leaft poffible Height of the Atmosphere.
31. To find the Law of Refraction.

32. To find the Refraction at any Inclination.
33. To find the Refraction at the given Height of a Star.
34. The Light of the Stars, particularly the Sun and
Moon, are reflected by the Particles of Air.

35. This

35. This Reflection is the principal Caufe of the Twilight. 36. When the Twilight begins.

37. The Height of the Air not to be found from the Quantity of the Twilight.

38. The Height of the Air, upon a Suppofition that a double Reflection is the Caufe of the Twilight. 39. The Height of the Air being given, to compute it's Quantity.

40. The Air bas certain Peculiarities, in certain Places.

CHAP. XX.

Of the Motion of the Air, Winds in general, and the Points of the Compass.

1. Winds defined.

Page 477

2. Moft Winds blow from one Point to the oppofite. 3. Points of the Compass defined.

4. The Number of Points and Winds.

5. Two and thirty Points and Winds.

6. A more accurate Enumeration of the Points and Winds.

7. The Winds according to the Antients enumerated. 8. Another Enumeration of the Winds.

9. Oppofite Winds.

10. Various Caufes of Winds.

11. Why Winds may blow perpendicularly to the Horizon of a Place.

12. Why the Winds blow not in continued, but interrupted Blafts.

13. Why Winds very feldom blow perpendicularly upon a Place from above, but generally oblique. 14. Why the South and West Winds are warm. 15. Why the Weft Winds blow feldomer than the East. 16. Why the North and Eaft Winds are stronger, and the South and Weft Winds weaker.

17. Why a fmall, thick, and blackish Cloud foretels Wind from that Quarter.

18. Why Winds are frequent in the Spring and Autumn.