Also the upper Stratum of Clouds thin and _white_, in _quick_ Motion, when seen from _below_ till Noon: at which Time the Sky was almost cloudless: and, from _above_ the upper Stratum, were seen, interspersed, Multitudes of detached Thunder-Clouds in large Masses, rising at Intervals, in the _Middle_ of the upper Surfaces of white Clouds, and stretching _above_ them. Friday and Saturday moderate: South and South-West Breeze. Sunday the 11th. The Planet Mercury stationary. Cloudy Morn. South-West Breeze. Thermom. at 60 at Noon. Barom. _above_, Changeable, viz. at 29½. +Much thunder+ and Rain in the Afternoon. 212. Quere, Had the _Thunder_-Clouds on Thursday, tho’ not remarked by any from +below+, yet visible to a great Extent from the Balloon _above_ them,—any Connexion with the _Thunder_ that happened +three+ Days after? [Sidenote: Weather, to be prognosticated, by _Sight_, from the Balloon] Answer: It appears to the Observer, that the _Thunder_ was _gradually_ collecting in the Air from _Thursday_ till Sunday: and if so; will not Balloons, when more _frequent_, prognosticate the Weather, _by Sight_, better than any other known Methods? CHAPTER XXXVIII. ON CERTAIN APPEARANCES AT DIFFERENT ALTITUDES OF THE BALLOON. [Sidenote: Of the highest visible Clouds which are always _white_.] Section 213. The highest visible _white_ Clouds, often seen in detached Streaks, during the finest and also in the worst Weather, (if not intercepted by lower Clouds) and which, when melting away, are known in some Counties by the common Appellation of Horse-Tails; and, suspended over Great-Britain, are frequently _marbled_ or dappled by the Wind; putting on the Appearance of white Waves, like Sea-Sands ruffled and left by a rapid Tide;—had been disturbed, separated, and almost _melted_ down by the _Storm_ the Day preceding the Excursion. Two of them _only_ were still visible in Streaks, near the Sun’s Place, at the first Ascent. They seemed without Motion, and became afterwards _invisible_. Saussure, the celebrated Professor of Philosophy at Geneva, is very exact in his Definition, Description, and Height of these Appearances: and thinks it _probable_, their Situation may be “_at least fifteen English Miles above the Surface of the Earth_.” “Car quand je considere ces fines Pommelures, &c.” “For when I consider these delicate Dapplings, which, in a Series of fair Weather, begin to cover the azure Vault of Heaven with a white and transparent Gauze, and which portend Rain a long Time before it happens; I am led to believe they occupy a very elevated Situation in the Atmosphere” (Essais sur l’Hygrometrie, P. 271.) It seems however that _Crosbie_, in his Excursion from Dublin on the 25th of January 1785, pierced throu’ and soared above these _fine Webs_, at the Height of 16 Inches by the Barometer in a _frosty_ Air. [Sidenote: Of the _Chilliness_ perceived at a certain Height.]