258. 2. For if the general Wind in the upper Current be not strong; the Aironaut may expect to be _becalmed_, with Respect to the horizontal Direction of the Current, the Instant he finds, by the Rise of the Barometer, that the Balloon _descends_; i.e. when it is acted upon by the depressing Column: in which Case, the _higher_ he has soared, the _safer_: as he will have more Room and greater _Latitude_ for Exertion by Means of the Machinery: which Machinery will be greatly _aided_ by the Force of the descending Column or Gravity; and will act on a similar Principle with the Ferry-Boats over the River Po in Italy; which are a Sort of horizontal Pendulum. For the Aironauts will continue to _descend_, at the same Time that their _Wings_ furnish the Means of a progressive Motion. Therefore, before the Time that the Balloon has reached the Surface of the Water; they will have crossed the depressing Column; and find themselves wafted _gently_ by the _new_ Sea-Breeze setting in towards the opposite Shore. 259. If the Aironaut _rises up_ to Sea with a Wind blowing from the Land on each of the opposite Sides of the Channel, and arrives above the Middle of the Channel, while the same Wind remains; it is probable that the Balloon will continue to rise higher as he proceeds towards the Middle, _where_ the +mediocèanal accumulation+ has for some Hours taken Place; and therefore he need not be under any Apprehension of falling: but, as before, it being probable he will also be _becalmed_; the Necessity of propulsive Machinery is equally urgent, in order to pass the Center of the _Accumulation_: after which, the Balloon will ride Home to the opposite Shore in the new Sea-Breeze, by _that_ Time, just beginning to set in. 260. With the Assistance of propulsive Machinery, it is imagined the Aironaut may be enabled in a few Minutes to force throu’ the calm mediocèanal Accumulation, or Depression: after which, he will have little Occasion to make Use of it. 261. +Sunrise+ is, probably, the +safest+ Time of all, to ascend towards the Sea, with an _Air-tight_ Balloon: arriving with the Assistance of the Wings, throu’ the _calm_ mediocèanal Accumulation: and there waiting till the new _Sea-Breeze_ sets in to the _opposite_ Shore. CHAPTER XXXXVII. [Sidenote: Difficulties, proposed by Mons. Sauffure stated; and their Solution attempted.] Section 259. It may be observed here, that the two Difficulties proposed by Sauffure, are, in a great Measure, removed; in admitting the Doctrine of mediocèanal _Depression_, and consequent alternate _Accumulation_, In a distinct Chapter, treating of the Variation of the Barometer, which he allows has Need of farther Explanation; he asks (Page 308) what Reasons can be assigned, why the _East_ Winds, which are _cold and dry_, make the Barometer _descend_, in England and Holland: yet, the _West_ Winds, which are _moist and temperate_, make it _rise_? The East Winds _here_ blow chiefly in Spring.