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CHA P. V.

A Definition of Steam, and an Account of

its various Qualities, Abilities, &c.

STEAM may be accounted a mixt fluid.

It is a vast Number of small Maffes

at small Distances one from another, comVid. p.20 of Salts. Po 2:20 posed of Corpuscles of Fire, or volatile

Salts, or Air put into Motion by the Gravities of other Bodies or Fluids, or some other Impulse joined to, theathed in, or entangled with Corpufcles of other fluids or Matter so small or light, and so figured, that the Malles or several Corpuscles of different Matter fo joined together, rise thro' Fluids, fome Distance into the Air, like Corpuscles of fire mixed with those of light dry Matter, which we call Sparks. When there are vaft Numbers of such successively raised and hindered from ascending upward, they may successively by their Motion, Rebounds, and

Elasticity impell one another through the - Fluid in any Direction, and jointly impell

what they meet with in their Passage. When they come to Corpuscles 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 some of them lie entangled in the fluid. If these Agents were not framed to entangle with other Matter, 'tis likely, they are so small, they might pass without moving a fluid, and they move faster or flower in Proportion to their burthens. Whether the Agents in each Mass keep the fame burthen which they take in the Stomach or Guts, and carry it through the blood to the Passes in the Lungs, or the capillary Vefsels, or Pores in the Skin, where the Cold clogs them, or they get out; or whether they change burthens in their Passage, and one take another's burthen, is not material. When these Agents go off alone, they are invi, sible, like Corpuscles of fire diffused; but when they go loaded in any considerable Number, near together, they form a vifible fume like Smoke, In Winter, when the Air is cool, it condenses the Steam issued out of the Lungs into Masses so large that they are visible. In Summer, when the Air is hot, it keeps them more divided, and more invisible. * That

Steam * Vid. Mart. Lifter Dissertat, de Humor, P: 76. Amfhelod, 1711,

Steam we discharge backward, commonly called Wind, they say will Fire at a Candle like the most volatile Spirits. When these Agents are entangled, or sheathed in Matter, whofe Corpuscles will not divide, or not divide small enough or light enough, for them to bear off, they are inactive like latent Corpuscles of Fire, &c. That Steam which is fo much loaded, that it goes not off briskly we call Wind. * All Fluids, except Air, will fall through Steam, though never so strong, and the Steam will give little Resistance, but when Steam issues and takes its Course through a small Tube, like a Flue to a furnace, it will resist any fluid, and repell it according to the Degree of its Impulse or successive Motion. When the Masses of the Steam are kept warm in a fluid, they keep separate, 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 such Quantity come there at once. There doubt

less

* And causes that uneasy Difension in the Bowels, we commonly say arises from Wind.

less does some small Quantity go with our Meat and Drink, and that if collected, would make a Stop in any Passage of the Body, because it will not pervade a Fluid alone; but when mixt with Corpuscles of Fire, small Salts, and Fluids it will pass any fluid in any Direction. The raising and bearing off Corpuscles of Solids in Steam, will not seem strange if we consider the smallness of the Corpuscles of Gold that can guild the Surface of 1000 of Yards of Silver Wire; * and how much smaller the Corpuscles of Vegetables, and Fluids may be. t. Or if you place a burning Candle near a smooth Body, and between it and the Sun, when it shines clear, you may see with how great. Velocity a prodigious Number of Corpuscles issue from the Candle. Steam will be compressed or expanded, when contained in any thing which can be ex-, tended, and contracted, as its Strength, or the Strength of that which compresses it, prevails. And the Strength of the Steam in the Stomach and Guts, or in some one, or part of them, is always equal at the present Bent, to the Pressure of the At

mosphere,

* Vid. Boyle Exp. de Atmosp. Cap. 2. Lugd. Bat. 167.6. it Consider the Size of a Pumpkin, in Comparifon of its Stalk, thro' which its whole Nourishment is conveyed.

mosphere, and the Resistance 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 several Valves, &c. might be circulated by Steam, issued out of a Vefsel into it, and the Compressure of the Air. But whether it be possible for Man to make the Parts so exact as to per: form it, I cannot tell. If such a Pipe had an End fixed in the side of a Veffel, which could be compressed, and would emit Steam into it, at a small Aperture, and at some 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 forward also, and the rest 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 defended from Cold, or Compressure be. tween the Vessel and the Bend, and a Valve were placed at the Bend to open forward with a small Force, when the second Valve opened, and beyond that Valve the Steam should be condensed by Cold, and suffered to perspire by Pores, and

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