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23. Oil of marjoram and similar oils have the effect of heat in burning the bones of the teeth.
24. Strong and well rectified spirit of wine has the effect of heat; insomuch that the white of an egg being put into it hardens and whitens almost as if it were boiled; and bread thrown in becomes dry and crusted like toast.
25. Aromatic and hot herbs, as dracunculus, nasturtium velus, &c, although not warm to the hand (either whole or in powder), yet to the tongue and palate, being a little masticated, they feel hot and burning.
26. Strong vinegar, and all acids, on all parts of the body where there is no epidermis, as the eye, tongue; or on any part when wounded and laid bare of the skin; produce a pain but little differing from that which is created by heat.
27. Even keen and intense cold produces a kind of sensation of burning;
Nec Bores penetrabile frigus adurit.1
28. Other instances.
This table I call the Table of Essence and Presence.
Secondly, we must make a presentation to the understanding of instances in which the given nature is wanting; because the Form, as stated above, ought no less to be absent when the given nature is absent, than present when it is present. But to note all these would be endless.
The negatives should therefore be subjoined to the affirmatives, and the absence of the given nature in
1 Nor burns the sharp cold of the northern blast.
, :.^r- £ in those subjects only that are most akin to
-.-r? in -which it is present and forthcoming. This
I --3-- ir- Ti:\ of Deviation, or of Absence in Proximity.
Z-r- .>.* in Proximity where the Nature of Heat is Absent.
1. The rays of the moon and of stars and .'^. comets are not found to be hot to the touch; indeed the severest colds are observed to be 4.: tie full moons.
The larger fixed stars however, when passed or approached by the sun, are supposed to increase and give intensity to the heat of the sun; as is the case when tie sun is in the sign Leo, and in the Dog-days.
To u» and. 2. The rays of the sun in what is called
the middle region of the air do not give heat; for
which there is commonlv assigned not a bad reason,
viz. that that region is neither near enough to the body
of the sun from which the rays emanate, nor to the
tfurth from which they are reflected. And this appears
iroui the fact that on the tops of mountains, unless they
*rv very high, there is perpetual snow. On the other
jj^xl it has been observed that on the peak of Teneriffe,
J.-V. Among the Andes of Peru, the very tops of the
3Ji-t;v.tains are free from snow; which lies only some
.»>.*: \nver down. Moreover the air itself at the very
j i- > found to be by no means cold, but only rare and
i\vi-; insomuch that on the Andes it pricks and hurts
rv e'vs bv its excessive keenness, and also irritates the
T.- v '.: of the stomach, producing vomiting. And it
%-*- ,'C**TWtl by the ancients that on the top of Olym
:v.^ vv rarity of the air was such that those who as
,\ ' vsx it had to carry sponges with them dipped in vinegar and water, and to apply them from time to time to their mouth and nose, the air being from its rarity not sufficient to support respiration; and it was further stated that on this summit the air was so serene, and so free from rain and snow and wind, that letters traced by the finger in the ashes of the sacrifices on the altar of Jupiter remained there till the next year without being at all disturbed. And at this day travellers ascending to the top of the Peak of Teneriffe make the ascent by night and not by day; and soon after the rising of the sun are warned and urged by their guides to come down without delay, on account of the danger they run lest the animal spirits should swoon and be suffocated by the tenuity of the air.
Tothe2od. 3. The reflexion of the rays of the sun in regions near the polar circles is found to be very weak and ineffective in producing heat; insomuch that the Dutch who wintered in Nova Zembla, and expected their ship to be freed from the obstructions of the mass of ice which hemmed her in by the beginning of July, were disappointed of their expectation, and obliged to take to their boat. Thus the direct rays of the sunseem to have but little power, even on the level ground; nor have the reflex much, unless they are multiplied and combined; which is the case when the sun tends more to the perpendicular; for then the incident rays make acuter angles, so that the lines of the rays are nearer each other; whereas on the contrary, when the sun shines very obliquely, the angles are very obtuse, and thus the lines of rays are at a greater distance from each other. Meanwhile it should be observed that there may be many operations of the sun, and those too depending on the nature of heat, which are not proportioned to our touch ; so that in respect of us their action does not go so far as to produce sensible warmth, but in respect of some other bodies they have the effect of heat.
To the 2nd. 4. Try the following experiment. Take a glass fashioned in a contrary manner to a common burning-glass, and placing it between your hand and the rays of the sun, observe whether it diminishes the heat of the sun, as a burning-glass increases and strengthens it. For it is evident in the case of optical rays that according as the glass is made thicker or thinner in the middle as compared with the sides, so do the objects seen through it appear more spread or more contracted. Observe therefore whether the same is the case with heat.
To the 2nd. 5. Let the experiment be carefully tried, whether by means of the most powerful and best constructed burning glasses, the rays of the moon can be so, caught and collected as to produce even the least xlegree of warmth. But should this degree of warmth prove too subtle and weak to be perceived and apprehended by the touch, recourse must be had to those glasses which indicate the state of the atmosphere in respect of heat and cold. Thus, let the rays of the moon fall through a burning-glass on the top of a glass of this kind, and then observe whether there ensues a sinking of the water through warmth.
To the 2nd. G. Let a burning-glass also be tried with a heat that does not emit rays or light, as that of iron or stone heated but not ignited, boiling water, and the like; and observe whether there ensue an increase of the heat, as in the case of the sun's rays.
To the 2nd. 7. Let a burning-glass also be tried with
To the 3rd. 8. Comets (if we are to reckon these too among meteors) are not found to exert a constant or manifest effect in increasing the heat of the season, though it is observed that they are often followed by droughts. Moreover bright beams and pillars and openings in the heavens appear more frequently in winter than in summer time, and chiefly during the intensest cold, but always accompanied by dry weather. Lightning, however, and coruscations and thunder, seldom occur in the winter, but about the time of great heat. Falling stars, as they are called, are commonly supposed to consist rather of some bright and lighted viscous substance, than to be of any strong fiery nature. But on this point let further inquiry be made.
To the 4th. 9. There are certain coruscations which give light but do not burn. And these always come without thunder.
To the 5th. 10. Eructations and eruptions of flame are found no less in cold than in warm countries, as in Iceland and Greenland. In cold countries too the trees are in many cases more inflammable and more pitchy and resinous than in warm; as the fir, pine, and others. The situations however and the nature of the soil in which eruptions of this kind usually occur have not been carefully enough ascertained to enable us to subjoin a Negative to this Affirmative Instance.
To the 6th. 11. All flame is in all cases more or less warm; nor is there any Negative to be subjoined. And yet they say that the ignis fatuus (as it is called), which sometimes even settles on a wall, has not much heat; perhaps as much as the flame of spirit of wine, which is mild and soft. But still milder must that flame be, which according to certain grave and trust