cause the Salt-Petre has fo much Air in it, tho' Chryftallized in Water, and reduced to little Tubes, I leave to the Judgment of others: It might however in fome manner leffen the Difficulty fome People make, as if Salt-Petre were too heavy, and not volatile enough to keep itself up in the Air.

V. This feems however to be entirely removed thereby; forafmuch as the Obfervations made by the new Burning-Glaffes fhew, that SaltPetre held in their Focus, entirely evaporates, and fo mingles itself with the Air, Hift. de l'Acad. &c. 1699. p. 114.

VI. All Metals, fuch as Silver, Iron, Copper, Lead, which are diffolved by the Spirit of SaltPetre, especially thofe upon which it acts with the greatest Force, as it does upon Iron, feem to ruft in the Air; only Gold, which a fimple Spirit of Salt-Petre can't touch, is not fo much expofed thereto All which gives a handle to a Conjecture, thar if there be not Salt-Petre itself, there is at least some Matter of the like Nature in the Air.

VII. A yet farther Proof that there is fomething Nitrous in the Air, feems to refult from the Pains in the Head, faintnefs and difpofitions to Vomit, which often appear in fome Women when they are in clofe Rooms, where a great many People and Stoves are. To be fatisfy'd of this Confequence, the Reader may be pleafed to recollect what we have fhewn above in the VIIth Contemplation, namely, that Flame and humane Refpiration are maintain'd by the fame kind of Air-Particles; for which reafon, the Air fhut up in a Room where a great many Stoves are burnVOL. III.

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ing, and a great many People breathing, must be very much divefted of thofe Parts, and be the Occafion that fome weak Women are disorder'd thereby. Now that these Parts are properly Nitre or Salt-Petre, which being render'd by the Warmth of the Fire and Breathing, unfit to dif charge its Functions, feems to appear from hence, that Women thus diforder'd, cannot recover themselves by any better Means that I know of, especially when the fresh Ait won't do, than by the ufe of a Nitrous Salt diffolved in Water, of which I have feen many Experiments, either by putting a little Salt-Pette or Sal-Prunille in their Mouths, and letting it diffolve, gently, and fwallow it down.

SECT. XII. Salt-Petre Jeems to come out of the North; proved by three Experiments.

SINCE now the first of the Experiments seems to prove, and the other to make it very probable, that the Air has either Salt-Petre in it, or fomething of a nitrous Quality; it will appear in fome manner from the following Experiments, that the fame, at least on our fide of the Equinoctial Line, proceeds chiefly from the North.

I. Not to mention that the Air is cold to a great Degree in the Northern Parts of the World, (as for the South Pole, we take no notice of it now) nor that Salt-Petre does after a particuJar manner produce fenfible Coldness, as we fee by putting of Bottles of Wine in Summer-time in Water, and throwing a good Quantity of SalePetre into it, which chills it fo much, that fome have thought that one might freeze Water thereby, but that I fhall not determine: From hence it may be confider'd, whether that Air which makes

makes fo many Mountains of Ice in the frigid Zone, and keeps them always undiffolved, muft not greatly abound with Salt-Petre.

II. To render this the more probable, we fhall add what the Learned Hambergorus relates from the Ephem. Barom. of Mr. Bernard Ramazzini ; that Gentleman fays, that the Excrefcence of Salt-Petre from old Walls made of Mortar and Stone, does mostly appear in Winter, and when the Northerly Winds blow; and that those who make it their Bufinefs to gather Salt-Petre, do at that time particularly fweep the Walls; and that they get more of that Matter from Walls that ftand to the North than to the South; which feems to prove plainly enough, that befides the general Impregnation of the Air with Salt-Petre, the Northern Air does mostly abound therewith, and that it is frequently brought from thofe Parts to us.

III. Now whether it may be inferr'd, that upon account of nitrous Salt, the Northerly Winds make the Air heavier, and that upon the turning of the Wind to that Corner, the Mercury does often rife in the Barometer, as many who have writ upon this Matter affirm, I fhall not here inquire after.

Now whether the Air be render'd heavier by the Northerly Winds (which bring along with them from the cold Regions, a thick and compos'd Air towards the South, as appears from the Thermometers, in which we may obferve, that Cold compreffes the Air, and as appears likewife by the Refraction of Light, which is affirmed to be greater in the North) or whether fuch Gravity of the Air proceeds from the Salt-Petre wherewith it is impregnated, or for other Reafons: They who ufe Barometers know very well, that the Vol. III. Rrr z heavier

heavier the Air is, and the higher the Quickfilver rifes, the less rainy and the more dry Weather may be expected. See the At Lipf. 1696. p. 213. from whence therefore, befides other Circumftances that may be peculiar to the Country of the Jews, the Reason in general may be affigned of that Expreffion in Solomon's Proverbs, Chap. xxv. ver. 23. The North Wind driveth away Rain, fince by the greater Weight of the Air, the watry Vapours remain floating therein, and cannot defcend in Rain.

SECT. XIII. Salt-Petre becomes active by thofe Particles in it that are Sulphureous, shewn by Experi

ments.

BUT fince Salt-Petre feems to be very unactive in its own Nature, infomuch as when put into a Melting-pot over the Fire, it does not exert the leaft active Faculty, even with great Heat; it may be neceffary to examine a little more closely, what it is that renders it Active (as Acids and Alcalies working upon each other) and how it comes to produce fuch Wonders.

Now the Bodies which are more peculiarly proper to produce fuch an Effect, are all fuch as come under the Denomination of Sulphur among the Chymifts; to which belongs common Sulphur itfelf in the first Place, and every Thing else that has Sulphur in it; fuch as Antimony, Turf, and Wood-Coal; and in general, all that has Fat or Oil in it, fuch as Tartar and the like.

Thus we fee that Sulphur or fulphureous Bodies, thrown into melted and glowing Salt-Petre, or elfe being mingled cold with the fame, and fet on Fire, are put into violent Motions, and the Mixture often turned into a sudden and confuming Flame So likewife we find that Tartar mingled

mingled with a like quantity of Salt-Petre, will be kindled with the fmallest Fire, and burn fo long, till the Oleaginous and other Parts of the Tartar are evaporated; after which there will remain a white Alcaline Sait, which is therefore called Salt of Tartar. After the fame manner we fee diffolved Salt-Petre mixed with beaten Charcoal, or Turf char'd, and thrown into the Fire, become active, and caft out Flames; where being continued till no more Flame is perceived, the Chymifts make of it an Alcaline Salt, which they call the fixt Salt of Nitre: But whether it may not more juftly be termed the fixt Salt of Coals, for the fame Reafon as t'other is called the Salt of Tartar, I leave to the Learned: At least, how very active Salt-Petre is render'd by Sulphur and Coals, Gunpowder furnishes us with a wellknown, or rather with a wonderful and terrible Inftance.

It must not be thought that these Matters cannot be kept up in the Air, as not being fine and fmall enough, because we have fhewn before, that befides a great many other different Particles, there are likewise those of Sulphur found in the Air. Thus we fee, that in the Mediterranean, and other Parts of the World that are more Southern than we, there is very great and frequent Thun-. der and Lightning, of which in Greenland (as I have been informed by one that has been often there) and here with us in Winter, very little is obferved. Now that this is occafion'd because the Air abounds with more Sulphur in the former Regions than in the latter, (whereas in Greenand there feems to be more of Salt-Petre only, which paffing from the Northern to the Southern Part, produces these Effects in Conjunction with the fulpureous Air) is allowed by many as a probable Thing.

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