produced to countenance fuch an opinion; it was therefore rejected: Nor was it capable of fufficient proof before the furprifing accidental discovery made by profeffor Mufchenbroek.--But fince that, and other fubfequent ones, we are furnish'd with evidences which fufficiently prove, that thofe affertions were not mere conjectures, but rather like predictions, which are now clearly verified and realized by the plainest facts.

155. Thofe invifible things,' that noble Lord tells us, were but little enquir'd into; altho' they were the things, which GOVERN NATURE principally:' Thofe fpirits or pneumaticals were fcarce known: Yet without the help of these, he affures us we can make no true analyfis and indications (as he expreffes himself) of the proceedings of nature.

This, we are now convinc'd, proves literally true; not only that fuch fpirits, or pneumaticals merely exift, but we have the highest evidence, even that of our fenfes, pointing out to us that very identical agent it felf, in a more confpicuous manner, and rendering it much more familiar and plain than ever we were able to do even the common air.

156. No doubt but that noble author and Sir Ifaac Newton meant one and the fame agent or medium, tho' the former varies a little from the latter in his term, and makes use of the plural number || whereas Sir Ifaac always speaks Pneumaticals.

in the fingular S..

157. But it is to be obferv'd, that in the course of our experiments we frequently difcover a much more rare, fubtile, active part of æther, which has not yet been confider'd, tho its effects are obvious, and the neglect of attending to them has been the occafion of various ambiguities. This fuperior part of it, (for so I must call it) tho' it feems infeparable from the fubtile medium, discoverable by electrical experiments, is yet remarkably evident in many other Phænomena of nature. For this more active part therefore, I am at a lofs for an adequate Term: Should I call it ESSENCE OF ETHER, fome would perhaps afk what I mean by fuch an effence, or elfe call it an unmeaning Term. I fhall therefore, for distinction's fake, take the hint from that great Author's Pneumaticals, and call it in brief, by its more original appellation, PNEUMA, or elfe, Spirit of Ether; and fhall crave the liberty of the promilcuous use of thofe Terms: For I find I fhall be constrain'd either to make use of them, or others fimilar to them; fince, as I fhall fhew, fome other agent exifts much more fubtile and active than even the electrical medium itself. As no fatisfactory method appears to folve the Phænomena of Nature without fuch a Pneuma or Spirit, I fhall in the first place produce my evidence to prove its existence; and though

$ Spirit, Subtile Medium, or Æther.

we

we have very clear glimpfes of it from the ef fects of many electrical experiments; yet in none more than one, which may be esteem'd purely phyfical.

158. Few wou'd imagine that fuch a fubtile active Agent or Spirit is inceffantly paffing or -efcaping as it were from the upper regions (thro' every vertical bar of iron or steel) to the earth, and as we fhall foon find, thro' every compafs needle from the fouth to the north end, and to all rarified limits, and particularly to accumulations of the electrical fluid fur rounding the rubb'd tube or globe.

159. The existence of fuch a Pneuma, or more fubtile part of æther, is prov'd by the following eafy experiment: If the lower end of a vertical rod of iron approach but the northend of a magnetic needle, that north-end flies from it, and if the bar follows it, it will drive the needle round and round the compafs. If it ftop, the fouth-end of the needle will tend to the lower-end of the Bar: Inftantly drop down the hand and the upper end of the Bar will drive the fouth-end round, and if the Bar stop, the north-end of the Needle is driven to it.

160. From thefe effects when duly confider'd, it alfo evidently appears, that the elastic Pneu ma is conftantly paffing thro' the pois'd magnetic needle from the fouth thro' the north end: If the Bar be inverted, yet ftill the upper and lower end of it produce the fame effects, for which ever is made the lower end,

it will still be the north end, and the uppermoft the fouth....

161. That fuch a fubtile Pneuma is conftantly defcending from the upper regions, and which effects are render'd fenfible by means of iron Bars, is evidently confirm'd by all fuch as have been any time in a vertical pofition as Tongs, Poker, &c. But efpecially by fuch as have remain'd a long time in fuch an erect pofition as the Bars of old Church-windows &c.

162. Are not these effects from the length of time the fame Pneuma, or moft fubtile active part, that has been paffing fwiftly and violent

thro' them in the fame channels, and which has worn them away as it were, and in a very particular manner; for the upper and lower ends of thofe ancient Bars when brought to the magnetic Needle act not only with much more vigour than a common Bar, but if they are inverted, the foremention'd Pneuma, tho' fo rare and elaftic, feems incapable of defcending thro them in the fame channels, as it did thro' the common Bar when inverted, either end of that when uppermost or lowermoft produces the fame effects, but no longer than it remains up permoft or lowermoft; whereas the old Win dow-bars act as natural magnets, and in the fame manner as fo many Loadstones, each end of which, when inverted, acts in the very fame manner as before, that is, the original lower end of the old Bar will ftill drive the north-end of the Needle, notwithstanding it is inverted and

made

made the upper end; and the original upper end of it will repel the fouth-end of the Needle.

163. I fhall now fhew the effects of this Pneuma in electrical experiments. past

N, B. This moft fubtile active part of the ætherial fluid cannot be the fame part which we obtain in our electrical experiments for two reafons, first, because in common experiments it pervades all metals indifferently, and in the fame manner; whereas, in the foregoing experiments the effects are render'd fenfible by means of iron Bars only; and fecondly, becaufe in electrical experiments it frequently appears from its effects, to act in a different manner from the electrical fluid as will be evident from the following, which if carefully attended to, many of the otherwise infuperable difficulties will disappear.

164. The electrical medium refuses as it were to come in contact with a glass Body, infomuch that tho' the Leyden experiment fucceed ever fo well, a bit of Glafs introduc'd into any part of the circuit prevents the operation; whereas, if, as at Sect. 148. a downy feather be fix'd on the top of a vertical wire and cover'd with a glass receiver, and if then a glafs tube be rubb'd at a foot distance from it, the feather will follow the hand that rubs the tube as freely and as vigorously as if nothing were between. Is not this a much more fubtile fpirit than the electrical medium, fince that

per