Supposing therefore such a Circulation, as above, 'tis to be considered that to the Northward of the _Indian_ Ocean there is every where Land within the usual limit of the Latitude of 30, _viz._ _Arabia_, _Persia_, _India_, _&c._ which for the same reason as the _Mediterranean_ Parts of _Africa_, are subject to unsufferable Heats when the Sun is to the North, passing nearly Vertical; but yet are temperate enough when the Sun is removed towards the other _Tropick_; because of a ridge of Mountains at some distance within the Land, said to be frequently in Winter cover'd with Snow, over which the Air, as it passes, must needs be much chill'd. Hence it comes to pass, that the Air coming according to the general Rule, out of the N. E. in the _Indian_ Seas, is sometimes hotter, sometimes colder, than that which by this Circulation is return'd out of the S. W. and by consequence, sometimes the under Current or Wind, is from the N. E. sometimes from the S. W. That this has no other Cause, is clear from the times wherein these Winds set in, _viz._ in _April_, when the Sun begins to warm those Countries to the North, the S. W. _Monsoon_ begins, and blows during the Heats till _October_; when the Sun being retir'd, and all things growing cooler Northward, and the Heat increasing to the South, the North-East Winds enter and blow all the Winter till _April_ again. And it is undoubtedly from the same Principle that to the Southwards of the Æquator, in part of the _Indian_ Ocean, the North-West Winds succeed to the South-East, when the Sun draws near the _Tropick_ of _Capricorn_; but I must confess, that in this latter occurs a difficulty, not well to be accounted for, which is, why this Change of the _Monsoons_ should be any more in this Ocean, than in the same Latitudes in the _Æthopick_, where there is nothing more certain than a S. E. Wind all the Year. 'Tis likewise very hard to conceive why the limits of the Trade-wind should be fixt, about the thirtieth Degree of Latitude all round the Globe; and that they should so seldom transgress or fall short of those bounds; as also that in the _Indian_ Sea, only the Northern Part should be subject to the changeable _Monsoons_, and in the Southern there be a constant S. E. These are Particulars that merit to be consider'd more at large, and furnish a sufficient Subject for a just Volume, which will be a very commendable Task for such, who being us'd to Philosophick Contemplation, shall have leisure to apply their serious Thoughts about it. [Illustration: _Plate 2 pag. 80_ A new & Correct SEA CHART of the WHOLE WORLD _Shewing the _Variations_ of yᵉ _COMPASS_ as they were found Año 1700 with a View of the Generall and Coasting _Trade Winds_ and _Monsoons_ or shifting _Trade Winds_ by the Direction of _Capᵗ. Edm. Halley_._]