That the former Air, in moderate Weather, shoud continue _warm and rarefied_: while the latter is _cool and condensed_. For the same Reason the Air over the Sea, on the Hours of Accumulation; i.e. during the Night, in Summer, and frequently in Winter, shoud be found _warm_ and _rarefied_: especially during a Continuance of the Apogay Winds. 277. It is likewise probable that the Atmosphere will be found +respirable+ at much greater Heights, than is at present imagined: during the Continuance of the Eknèfiai Winds; and also, on Account of the _defloguisticated_ Air,[83] which is _drier_ and _less elastic_ in Proportion to its Rarity.[84] 278. The Height of 10 Miles seems not too great to limit human Respiration, shoud any Attempt be made, to soar with a Balloon in a mild Atmosphere; and particularly between the Tropics.[85] But an Objection woud be found in the Size of a Balloon sufficiently capacious to contain nearly 6 Times the Bulk to which the Gass woud necessarily expand itself, at the Height of 10 Miles. [Sidenote: First Cause of Limitation, in the Ascent of Balloons.] [Sidenote: Second Cause of Limitation in the Ascent of Balloons.] 279. It seems most likely that the primary Cause that will affect the Ascent of Balloons is the Difficulty of encreasing the Dimension of the Balloon: the Second, is from the excessive Cold; if the Wind blows from any Points of the North. Supposing the Construction of the Atmosphere to be as represented by different Authors, (which, by the Way, is scarcely credible) ten Miles will perhaps be the utmost attainable Height. 280. There is a Circumstance relative to the Motion of the Air, which has not been sufficiently attended to: and bears some Analogy with that of a _Thorough Air_. This Circumstance may not improperly be called the _Reception_ and _Dispersion of Air_. In cold Climates, it is an Object of Dread: in warm ones, a most desirable Piece of Luxury. A gentle Undulation of the Air is perceived in Peru, and other hot Climates, by Persons sitting in _Arbours_ sheltered from the Sun. The surrounding Air is instantly _contracted_ by _Condensation_, during the Absence of the Sun’s Rays, and therefore occupies a _less Space_: _fresh Air_ is _received_, and as instantly _dispersed_ by Expansion towards those Parts, which are the warmest, i.e. where there is least Resistance: so that a gentle Breeze is constantly kept up, _probably_ by a Depression from _above_.[86] 281. Analagous to this, are those Winds which generally _rise early_ and die away at _Sunset_: the nocturnal Condensation of the Air being sufficient for the +reception+: as Air suffers some Compression without Tumult.