On the motion of the flame.

The flame that is born has a swift birth and a swift life and death. Its principal first motion is upward; the second principal motion is toward the place of its exhalation; the least is downward. And it does not approach any dense body — unless red-hot and burning — except by an impetuous motion, which brings it into contact with the opposing objects, and from these it rebounds, but not at equal angles, as is seen to happen with many other powers. The flame is condensable to infinity, as that which is condensed in bombards shows us: they compress it into such density that it exceeds that of the very material of the bombards, with an excess as much greater as the material of the bombard exceeds the air. We shall say it better: the flame is condensable to infinity, as that which is condensed in bombards shows us, which becomes so much denser than the material of the bombard itself that it overcomes it with such power that it makes it fly into pieces through the air, as a thing of as much greater lightness than fire as fire is lighter than air, and so on. The free motion of fire, the more it moves upward, the swifter it becomes, just as is seen with a heavy body moving downward. And it is bendable through any winding conduit without loss or diminution of its equal speed; and if this were not so, it would follow that where it had continual retardation, the preceding quantity would separate from the succeeding quantity, and thus a vacuum would be generated between these separations, which is impossible. Therefore it is necessary that such motion of the flame be uniform in every part of its length; but it is not compelled to have uniform motion in any part of its thickness, unless the width of that conduit were itself uniform. The flame that moves through a conduit of various widths will have various motions within itself, that is, winding, whirling, retrograde and straight, which motions it will make in the thickness of the flame; and as much as one of the sides is retarded, so much does the opposite side become swifter in proportion, so that in every part of such a conduit an equal quantity of flame passes in equal time. The flame will be the brighter the denser it is, and conversely will be the less bright the rarer it becomes, and so on.

The flame does not extend in length without being pyramidal, unless it passes through a burning conduit. The flame bends where its exhalation has fed it. The flame that condenses too much dies at once. Where the air is not suited to receive the flame, no flame can live there, nor any land or air animal.
If all the bases of a number of equal flames are everywhere touching one another, they will make of themselves one continuous flame, which, having sufficient and continuous nourishment, will make of themselves a pyramidal fire, similar in shape to each of the aforesaid flames taken separately from the others. But it seems that such a flame ought to be of equal thickness within itself from below to above; and this is proved with certainty, because if all such flames clothed the sphericity of the earth — granting that it were of perfect sphericity — then it would be necessary that such a garment of flame should clothe the earth with equal thickness, because every flame flees in a straight line toward the surrounding sphere of fire.
Of the heat and colour of fire no science is given, neither of its nature nor of the colours of glass and other things that are engendered in it; but of its motions and other accidents, yes, and of making it increase and diminish in power, and of the transmutation of colours in its flames in as many diverse ways as there are varieties of the materials that nourish it or that are infused into it. And it is multipliable within itself to infinity, and immediately so in the infinite gunpowder that might be given to it; and granting that one could give it as much powder as the four elements, one asks what office, or what motion, it would perform upon the sphere of fire, and what that sphere would do to itself, and so on.

Smoke(?) to dissolve bronze(?)

The smoke is generated in the middle of the candle flame.

The smoke that first arises in the little sulphur match is blue and spherical.

That motion of the flame will be swifter which moves through a space of greater heat, and conversely it will move more slowly which passes through a place of greater cold.

Of flames of equal size, that will be of greater heat which is the more splendid. The converse follows.
Of flames of equal magnitude the more splendid is the swifter. The converse follows.

...pr... to the flame, cannot receive it with life.
Where the flame does not live, no animal that breathes lives.

Excessive wind kills the flame, and temperate wind nourishes it.
That flame makes a greater sound with the air it penetrates, into which the air enters with greater fury.
The flame first disposes the material that is to nourish it, and then it feeds on it. The moist becomes lighter the more it dilates, and becomes heavier the more it is heated. If water that passes through a vent beneath other water will make a sound beneath that water, as air does that passes through a whistle amid the air? It seems not, because water, although it is liquid like air, is not condensable as air is.

The middle of the thickness of the smoke, being lighter than the air, rises amid that air, and the sides of that smoke fall back downward, because they become heavier than the air.

[The] air interposed between the fire and the water is the mediator of equal flights; for if the water is drawn up into the air and then let free, it will descend to the water and penetrate it until it exhausts the heaviness generated by the impetus; and the fire drawn up into the air, once it is let free, will return to the fire, penetrating it until it exhausts the acquired impetus.
Whether the hail has a whirling motion in descending through the air or not.
The hail that descends through the air has no whirling motion, because if it is round, the descent is straight in the parts of equal weight; and if it is not round, the descent is still straight, because in heavy bodies that descend through the air, the heavier part makes itself the guide of the motion.
Whether the descent of the hail consumes its quantity.
Whether the descent of the hailstone diminishes the quantity of its weight: if it is not of whirling motion and has in part to be consumed, the part of its consumption will be lateral and not above, but below and at the sides, and thus it will remain of pyramidal shape; and since it does not show itself pyramidal at the end of its descent, it is manifest that the descent of the hail does not diminish its quantity.
And if you say that such hail in descending dissolves in great part into water, this is denied, because every heavy body that descends becomes the swifter the more it descends, and that thing which is more accelerated cools more, and consequently freezes more. Therefore, by the increased motion, the hail condenses, and for this reason it does not dissolve into water.
Of the heat that withdraws to the middle of the cloud raised by it.
The heat infused into the cloud makes it lighter, of greater lightness than the air, and for this reason it rises upward toward the cold region of the air, where the heat, repelled by the cold, withdraws toward the middle of the cloud and stops at that height, where the cold resists the rising of the heat and the heat prevents the penetration of the cold. Therefore the two contrary powers of heat and cold are made equal, and because things equal to one another do not overcome one another, it is necessary that such a cloud be resolved by the heat that was infused into it, and then its destruction will follow. But if we have posited such powers as equal — that is, the heat and the cold — it is necessary that the one be not consumed by the other, and for this reason we should have to conclude that the situation and shape of such a cloud would be eternal; but because such eternity is not granted to us by experience — since no cloud has permanence either of its shape or quantity — we must find the true cause of its destruction, and this is the wind, which, striking, will break and roll up the parts of such a cloud and mingle together the heat and the moist along with the cold, and generate a furious discord of water, rain, hail and wind, and so on.
Example of the smoke.
The motion of the smoke, the more it rises, the more it slows, and it seems it ought to be the contrary, since the heat, the more it approaches its natural place, the swifter it becomes. But this happens because the heat that generates the smoke, at every degree of the smoke's elevation, acquires degrees of diminution for two causes: one is that the more it rises, the more it finds cold air; the second is that the more it rises, the more it loses of the impetuous motion by which it was converted from flame into smoke; and one may also add a third cause, namely, that the more it rises, the longer becomes the time of its creation. The middle part of the smoke rises to a greater height than any other part, that is, the middle part of its thickness. The converse follows, which says: the lateral parts of the smoke are the slower the more remote they are from the middle of the thickness of that smoke; and this happens because that middle smoke, being defended from the cold by the thickness of the smoke that clothes it, keeps itself hotter than the outer parts of the same smoke.