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57) [Left Margin] Astronomical Table for variation of Compass [/Margin] "They write from Scotland, that the Rev. Mr. Dingwall, an eminent mathematician, has lately invented a set of Astronomical Tables, calculated for discovering the variation of the Compass in any latitude, without having recourse to the old method of observing either by azimuth or amplitude" Cambridge Chronicle for September 7th 1765. [Right Margin] Magnetism thought to be fire. [/Margin] [Left Margin] His Majesty's WATCH, shews time to a 300th pt. of a minute [/Margin] "The new watch made for his Majesty by Mr. Arnold, shews the time to a 300th part of a minute, winds up by one push of the pendent, and continues going during that time; all the holes in the watch are jeweled, and it is allowed by judges to be the compleatest piece of workmanship in this kingdom." D.[[superscript]] o [[/superscript]] Chronicle for D.[[superscript]] o [[/superscript]] [Right Margin] Soft iron receives it soonest, but retains it [[insertion]] the [[/insertion]] least time. [/Margin] Cause of Thunder. The fire, made apparent in electrical experiments, pervades and adheres to most bodies; while it flies, and cannot be brought to mix with some particular bodies; it flies & shuns air, but pervades water more intimately than almost any other body: and it not only pervades, but also surrounds & covers them to a certain distance from their superficies, in proportion to the state of its activity, which is increased by heat: moreover, when it is artificially or accidently protruded upon any body beyond its natural affection, it will fly off to the next approaching body, which is not so much impregnated with this fire; and when it departs in any considerable quantity, it makes a great noise or crack: [Right Margin] The condition of the Earth & Clouds at the time of Thunder. [/Margin] Now, to shew, that this fire is the real cause of thunder, we need only consider it attending every vessel of humid vapour rising into the atmosphere, and covering its superficies to a certain depth; which I think it must certainly do. (How far this fire is the cause of vapours ascending is left for a future number) Now, in the collision to form the drops, descending much larger than the vesicles, in which it ascended, we must consider what becomes of our fire; for the surface of these larger drops increasing only as the squares, but their solids as the cubes of their diameters, the fire, which surrounded the superficies of the vesicles, must be protruded to a much greater distance from the superficies of the larger drops, & by that means made more in proportion to the larger drops, than its natural affection would have made it join them with; &, consequently, rend'red more apt to fly off to the next approaching or approached body, not so fully impregnated by this fire. [Right Margin] Seasons periodical. Why an Hot or Dry summer is succeeded by a Cold or Wet winter. [/Margin] The constant seat of thunder is in those clouds, which are most compact of humid vapour, and which descend in the heaviest showers, and that generally in warm weather, when the adjacent atmosphere is serene; so that the humid vapours are almost all collected into this chain of clouds; where, according to the compaction, there will be a body of this fire collected, and ready to fly off, sufficient to perform the greatest effects of thunder. Now some of these clouds coalescing in their descent, and the drops increasing in their magnitude , there is a vast body of this fire collected more than what would naturally adhere to those drops and their surfaces; which being rendered more active in its vibrations, by the heat of the lower part of the atmosphere, the sphere of its affections (pardon the word, [[strikethrough]] for I have [[/strikethrough]] for I have no other) is also increased in proportion to the body of fire, which enables it to fly off to clouds, no so much impregnated, at a considerable distance, with that violent crack so much taken notice (continued on p.59.)
Transcription Notes:
'shews' is an old way of saying 'shows'https://transcription.si.edu/contact
