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must own, is something unprecedented : But as Facts are so stubborn as to yield to no Reasoning, tho' ever so plausible, the following indubitable ones are exhibited, to evince that such an universal primary Air or Æther, not only exists in gross Bodies, but is also clearly verified to the Senses : Universal I say, since it manifestly appears to be so, as far as human art and industry can pursue it ; i. e. as far as the Clouds, and must therefore be allow'd. See Sir Isaac's third Rule of Reasoning.

55. That the existence of such an universal primary Air or Æther was long ago perceiv'd, is evident from many of the Writings of the ancient Philosophers; and the same doctrine has been adopted and cultivated from time to time by many eminent moderns, and particu·larly by some of our own Countrymen, as the great Lord Bacon, the

indefatigable Mr. Boyle, the learned - Prelate Dr. Berkeley, Bishop of Cloyne,, and especially the great Sir Isaac Newton.

56. But before I produce the Experiments that

prove it to exist in the pores of gross bodies, as Sir Isaac had asserted, I shall endeavour to obviate an objection or two that may possibly be made to some particular Articles of my Theory, that they may appear to others in the same rational and convincing Light in which they do to my self.

felf. As 57 I. What reasonable pretence there can be for supposing two distinct Airs.

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II. What Properties the electrical Æther has in common with Air.

III. What Properties it has in common with the Æther or pure Air, viz. fuch Properties of it, as are ascribed to it by Sir Isaac Newton, and the learned Prelate before mentioned.

58. First, That the opinion of two kinds of Air, distinct from each other, is not a mere Novelty: This appears from Chambers's Ency, clopædia, as well as from the before-mention'd Siris : And herein Bishop Berkeley seems not only to favour such an Opinion himself ; but informs us, that · Æther by the ancient Phi.

losophers was used to signify promiscuously, • sometimes Fire and sometimes Air. For they

distinguish'd two sorts of Air. Plato in the • Timæus speaking of Air, faith, there are two • kinds, the one more fine and subtile, called ç æther, the other more gross and replete with vapours.

Sect. 168. Sir Isaac Newton also seems to be of the fame Opinion

59. I. •I suppose', says he, that there is dif• fus'd through all places an ætherial substance, ? capable of contraction and dilatation, strongly ! elastic, and, in a word, much like Air in all e respects, but far more subtile.'

60. II. I suppose this æther pervades all

gross bodies, but yet fo as to stand rarer in s their pores than in free spaces, and so much & the rarer as their pores are less. ' & Ca See Sir Isaac Newton's Letter to Mr. Boyle, written

in the Year 1678. Again,

61. Secondly, A most remarkable congruity appears between this Fluid and the common Air in almost every respect. The electrical Fluid is possessed of every property belonging to the common Air, both effential and accidental, ( unless that of ponderosity or gravity may be excepted t. ,) viz. rarity, subtilty, and elasticity; is capable of dilatation and contraction; their particles, like those of common Air, mutually repel and recede from each other, altho' in a much greater degree. But if the electrical fluid is destitute of one property belonging to the common Air, there are others belonging to the electrical Auid, not to be found, or at least, not to be easily render'd sensible in common air ; e. g. the common air seems almost incapable of exhibiting any signs of light or fire ; nor can it bę render'd visible like electrical or pure air.

62. Another property seems common to both the electrical and the gross air, which is this

i the gross air contain'd in the sensible pores of the most rare hollow bodies, is capable of being heated by friction, as well as the electrical and more pure air contain'd in the mia

+ I have attempted to prove it by as accurate a balance as I cou'd well procure, but cou'd never perceive the least gravitating Property belonging ta


nutest porcs

of the most dense metals, but in á much less degree ; and two sticks of the rarest dry hard wood, when rubb’d together will grow

hot as well as metallic bodies, altho' as was before observ'd, in a much less degree. And the indefatigable Boerhaave, who had made a number of those experiments, informa us, that two gold plates may be rubb’d together till they grow so hot, as to be just at the point of melting : The pure Air or Fire, contain'd in the minute pores of the gold, seem much more capable of receiving an intense heat, than the more gross Air contain'd in the sensible pores

of those rare, hollow, light bodies ; and yet we find even that in those bodies, will grow so hot, by means of violent friction, as to be frequently kindled into an actual fame.

63. The Third and principal thing to be examin'd is, whether the electrical Air be ena dued with the same natural qualities and properties which are ascrib'd to Æther by Sir Ifaac Newton, c.

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ExperimENTS, which shew, ihat the

électrical Fluid is endued with the two inherent or effential Properties of Æther, and in a mofi surprising degree, namely those of extreme Rarity, and extreme Elasticity. ***H O' almost every Experiment either T illustrates or demonstrates the great

Rarity and Elasticity of the electrical

Fluid ; yet none more than the Leyden Experiment, which Shock and Explosion are entirely owing to the alternate exertion of those two properties, particularly in some of Dr. Franklin's capital Experiments, of which the following is a Specimen.

65. That ingenious and approv'd Experimentalist, in order to examine into the surprising force of that moft wonderful Phænomena of Nature, just discover'd, namely, the ELECTRICAL SUBTILE MEDIUM, had contriv'd a Device, which he call’d a magical Picture, by means of which he could strike a hole thro'


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