of Salts.

CHAP. V.

A Definition of Steam, and an Account of its various Qualities, Abilities, &c.

STEAM may be accounted a mixt fluid.

It is a vaft Number of fmall Maffes

at small Distances one from another, comVid. p.20 pofed of Corpufcles of Fire, or volatile Salts, or Air put into Motion by the Gravities of other Bodies or Fluids, or fome other Impulse joined to, fheathed in, or entangled with Corpufcles of other fluids or Matter fo fmall or light, and fo figured, that the Maffes or feveral Corpufcles of different Matter fo joined together,. rife thro' Fluids, fome Distance into the Air, like Corpufcles of fire mixed with those of light dry Matter, which we call Sparks. When there are vaft Numbers of fuch fucceffively raised and hindered from afcending upward, they may fucceffively by their Motion, Rebounds, and Elafticity impell one another through the Fluid in any Direction, and jointly impell what they meet with in their Paffage. When they come to Corpufcles of Cold, these Corpuscles adhere to the Maffes,

over

overload the Agents, and they and their Burthens fall. Their burthens collected, form a fluid, and the Agents by Degrees go off freed, with smaller burthens, or perhaps fome of them lie entangled in the fluid. If thefe Agents were not framed to entangle with other Matter, 'tis likely, they are fo fmall, they might pafs without moving a fluid, and they move fafter or flower in Proportion to their burthens. Whether the Agents in each Mafs keep the fame burthen which they take in the Stomach or Guts, and carry it through the blood to the Paffes in the Lungs, or the capillary Veffels, or Pores in the Skin, where the Cold clogs them, or they get out; or whether they change burthens in their Paffage, and one take another's burthen, is not material. When thefe Agents go off alone, they are invifible, like Corpufcles of fire diffused; but when they go loaded in any confiderable Number, near together, they form a vifible fume like Smoke. In Winter, when the Air is cool, it condenfes the Steam iffued out of the Lungs into Maffes fo large that they are vifible. In Summer, when the Air is hot, it keeps them more divided, and more invifible. * That Steam

* Vid. Mart. Lifter Differtat. de Humor, p, 76. Amfeled, 1711.

Steam we discharge backward, commonly called Wind, they fay will Fire at a Candle like the moft volatile Spirits. When thefe Agents are entangled, or fheathed in Matter, whofe Corpufcles will not divide, or not divide small enough or light enough, for them to bear off, they are inactive like latent Corpufcles of Fire, &c. That Steam which is fo much loaded, that it goes not off brifkly we call Wind. * All Fluids, except Air, will fall through Steam, though never fo ftrong, and the Steam will give little Refiftance, but when Steam iffues and takes its Course through a fmall Tube, like a Flue to a furnace, it will refift any fluid, and repell it according to the Degree of its Impulse or fucceffive Motion. When the Maffes of the Steam are kept warm in a fluid, they keep feparate, and infinuate and mix themselves in it, till the Supply cease, or the fluid cool, or the Agents go off, or be overloaded. When they are condensed alone, they form a thin Fluid. I know it is a common Notion that it is Wind or Air which extends the Stomach and Guts, but 'tis certain there can no fuch Quantity come there at once. There doubtlefs

And caufes that uneafy Diftenfion in the Bowels, we commonly fay arifes from Wind.

lefs does fome small Quantity go with our Meat and Drink, and that if collected, would make a Stop in any Paffage of the Body, because it will not pervade a Fluid alone; but when mixt with Corpufcles of Fire, fmall Salts, and Fluids it will pafs any fluid in any Direction. The raifing and bearing off Corpufcles of Solids in Steam, will not feem ftrange if we confider the smallnefs of the Corpufcles of Gold that can guild the Surface of 1000 of Yards of Silver Wire; * and how much smaller the Corpufcles of Vegetables, and Fluids may be. + Or if you place a burning Candle near a smooth. Body, and between it and the Sun, when it fhines clear, you may fee with how great Velocity a prodigious Number of Corpufcles iffue from the Candle. Steam will be compreffed or expanded, when contained in any thing which can be ex-. tended, and contracted, as its Strength, or the Strength of that which compreffes it,, prevails. And the Strength of the Steam in the Stomach and Guts, or in fome one, or part of them, is always equal at the prefent Bent, to the Preffure of the Atmosphere,

* Vid. Boyle Exp. de Atmofp. Cap. 2. Lugd. Bat. 1676. + Confider the Size of a Pumpkin, in Comparifon of its

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Stalk, thro' which its whole Nourishment is conveyed.

mosphere, and the Refiftance of the Mufcles of the Belly, &c. because these are always acting against it.

'Tis poffible to conceive, how a Fluid in a Pipe, with feveral Valves, &c. might be circulated by Steam, iffued out of a Veffel into it, and the Compreffure of the Air. But whether it be poffible for Man to make the Parts fo exact as to perform it, I cannot tell. If fuch a Pipe had an End fixed in the Side of a Veffel, which could be compreffed, and would emit Steam into it, at a fmall Aperture, and at fome Distance had a Valve in it, which that Steam would force open in a Second of Time, and at a little Distance beyond that another Valve, to open for ward also, and the reft of the Pipe were filled with a Fluid, and were bended, and the other End were fixed into the Side of the Pipe, between the two Valves, immediately after the first, with a Valve to open into the Pipe, and the Pipe were de fended from Cold, or Compreffure between the Veffel and the Bend, and a Valve were placed at the Bend to open forward with a fmall Force, when the fecond Valve opened, and beyond that Valve the Steam fhould be condensed by Cold, and fuffered to perfpire by Pores, and

the