XII we must next present to the understanding instance which do not admit of  the give nature for from as we have observe ought no less to be absent where  the give nature be absent than to be present where it be present if however we  be to examine every instance our labour will be infinite negative therefore  must be class under the affirmative and the want of the give nature must be  inquire into more particular in object which have a very close connection with  those other in which it be present and manifest and this we be wont to term a  table of deviation or of absence in proximity proximate instance want the  nature of heat the ray of the moon star and comet be not find to be warm to  the touch nay the severe cold have be observe to take place at the full of the  moon yet the large fix star be suppose to increase and render more intense the  heat of the sun as he approach they when the sun be in the sign of the lion  for instance and in the dog-day the ray of the sun in what be call the middle  region of the air give no heat to account for which the common assign reason  be satisfactory namely that that region be neither sufficient near to the body  of the sun whence the ray emanate nor to the earth whence they be reflect and  the fact be manifest by snow be perpetual on the top of mountain unless  extreme lofty but it be observe on the other hand by some that at the peak of  teneriff and also among the Andes of Peru the top of the mountain be free from  snow which only lie in the low part as you ascend beside the air on the summit  of these mountain be find to be by no mean cold but only thin and sharp so  much so that in the Andes it prick and hurt the eye from its extreme sharpness  and even excite the orifice of the stomach and produce vomit the ancient also  observe that the rarity of the air on the summit of Olympus be such that those  who ascend it be oblige to carry sponge moisten with vinegar and water and to  apply they now and then to their nostril as the air be not dense enough for  their respiration on the summit of which mountain it be also relate there  reign so great a serenity and calm free from rain snow or wind that the letter  trace upon the ash of the sacrifice on the altar of Jupiter by the finger of  those who have offer they will remain undisturbed till the next year those  even who at this day go to the top of the peak of teneriff walk by night and  not in the daytime and be advice and press by their guide as soon as the sun  rise to make haste in their descent on account of the danger apparent arise  from the rarity of the atmosphere lest their breathe shall be relax and  suffocate the reflection of the solar ray in the polar region be find to be  weak and inefficient in produce heat so that the Dutch who winter in new  Zembla and expect that their vessel will be free about the beginning of July  from the obstruction of the mass of ice which have block it up be disappoint  and oblige to embark in their boat hence the direct ray of the sun appear to  have but little power even on the plain and when reflect unless they be  multiply and condense which take place when the sun tend more to the  perpendicular for then the incidence of the ray occur at more acute angle so  that the reflect ray be near to each other while on the contrary when the sun  be in a very oblique position the angle of incidence be very obtuse and the  reflect ray at a great distance in the meantime it must be observe that there  may be many operation of the solar ray relate too to the nature of heat which  be not proportion to our touch so that with regard to we they do not tend to  produce warmth but with regard to some other body have their due effect in  produce it let the follow experiment be make take a lens the reverse of a burn  glass and place it between the hand and the solar ray and observe whether it  diminish the heat of the sun as a burn glass increase it for it be clear with  regard to the visual ray that in proportion as the lens be make of unequal  thickness in the middle and at its side the image appear either more diffuse  or contract it shall be see therefore if the same be true with regard to heat  let the experiment be well try whether the lunar ray can be receive and  collect by the strong and best burn glass so as to produce even the least  degree of heat but if that degree be perhaps so subtle and weak as not to be  perceive or ascertain by the touch we must have recourse to those glass which  indicate the warm or cold state of the atmosphere and let the lunar ray fall  through the burn glass on the top of this thermometer and then notice if the  water be depress by the heat let the burn glass be try on warm object which  emit no luminous ray as heat but not ignite iron or stone or hot water or the  like and observe whether the heat become increase and condense as happen with  the solar ray let it be try on common flame the effect of comet if we can  reckon they among meteor in augment the heat of the season be not find to be  constant or clear although drought have general be observe to follow they  however luminous line and pillar and open and the like appear more often in  winter than in summer and especial with the most intense cold but join with  drought lightning and coruscation and thunder however rare happen in winter  and general at the time of the great heat the appearance we term fall star be  general suppose to consist of some shine and inflame viscous substance rather  than of violent hot matter but let this be further investigate some  coruscation emit light without burn but be never accompany by thunder  eructation and eruption of flame be to be find in cold climate as well as in  hot as in Iceland and Greenland just as the tree of cold country be sometime  inflammable and more pitchy and resinous than in warm as the fir pine and the  like but the position and nature of the soil where such eruption be wont to  happen be not yet sufficient investigate to enable we to subjoin a negative  instance to the affirmative all flame be constant more or less warm and this  instance be not altogether negative yet it be say that the fire fatuus as it  be call and which sometime be drive against wall have but little heat perhaps  it resemble that of spirit of wine which be mild and gentle that flame however  appear yet mild which in some well authenticate and serious history be say to  have appear round the head and hair of boy and virgin and instead of burn  their hair mere to have play about it and it be most certain that a sort of  flash without any evident heat have sometime be see about a horse when sweat  at night or in damp weather it be also a well know fact and it be almost  consider as a miracle that a few year since a girl apron sparkle when a little  shake or rub which be perhaps occasion by the alum or salt with which the  apron be imbue and which after have be stick together and incrust rather  strong be break by the friction it be well know that all sugar whether candy  or plain if it be hard will sparkle when break or scrape in the dark in like  manner sea and salt water be sometime find to shine at night when strike  violent by the oar the foam of the sea when agitate by tempest also sparkle at  night and the Spaniard call this appearance the sea lung it have not be  sufficient ascertain what degree of heat attend the flame which the ancient  sailor call Castor and Pollux and the modern call saint Ermus fire every  ignite body that be redhot be always warm although without flame nor be any  negative instance subjoin to this affirmative rot wood however approach near  to it for it shine at night and yet be not find to be warm and the putrefy  scale of fish which shine in the same manner be not warm to the touch nor the  body of the glow worm or of the fly call Lucciola the situation and nature of  the soil of natural warm bath have not be sufficient investigate and therefore  a negative instance be not subjoin to the instance of warm liquid we may  subjoin the negative one of the peculiar nature of liquid in general for no  tangible liquid be know that be at once warm in its nature and constant  continue warm but their heat be only superinduce as a adventitious nature for  a limit time so that those which be extreme warm in their power and effect as  spirit of wine chemical aromatic oil the oil of vitriol and sulphur and the  like and which speedy burn be yet cold at first to the touch and the water of  natural bath pour into any vessel and separate from its source cool down like  water heat by the fire it be however true that oily substance be rather less  cold to the touch than those that be aqueous oil for instance than water silk  than linen but this belong to the table of degree of cold in like manner we  may subjoin a negative instance to that of warm vapour derive from the nature  of vapour itself as far as we be acquaint with it for exhalation from oily  substance though easy inflammable be yet never warm unless recent exhale from  some warm substance the same may be say of the instance of air for we never  perceive that air be warm unless confine or press or manifest heat by the sun  by fire or some other warm body a negative instance be exhibit in weather by  its coldness with a east or north wind beyond what the season will lead we to  expect just as the contrary take place with the south or west wind a  inclination to rain especial in winter attend warm weather and to frost cold  weather a negative instance as to air confine in cavern may be observe in  summer indeed we shall make a more diligent inquiry into the nature of confine  air for in the first place the quality of air in its own nature with regard to  heat and cold may reasonable be the subject of doubt for air evident derive  its heat from the effect of celestial body and possible its cold from the  exhalation of the earth and in the mid region of air as it be term from cold  vapour and snow so that no judgement can be from of the nature of air by that  which be out of door and expose but a more correct one may be derive from  confine air it be necessary however that the air shall be enclose in a vessel  of such material as will not imbue it with heat or cold of themselves nor easy  admit the influence of the external atmosphere the experiment shall be make  therefore with a earthen jar cover with fold of leather to protect it from the  external air and the air shall be keep three or four day in this vessel well  close on open the jar the degree of heat may be ascertain either by the hand  or a graduate glass tube there be a similar doubt as to whether the warmth of  wool skin feather and the like be derive from a slight inherent heat since  they be animal excretion or from their be of a certain fat and oily nature  that accord with heat or mere from the confinement and separation of air which  we speak of in the precede paragraph for all air appear to possess a certain  degree of warmth when separate from the external atmosphere let a experiment  be make therefore with fibrous substance of linen and not of wool feather or  silk which be animal excretion for it be to be observe that all powder where  air be manifest enclose be less cold than the substance when whole just as we  imagine froth which contain air to be less cold than the liquid itself we have  here no exact negative instance for we be not acquaint with any body tangible  or spirituous which do not admit of heat when expose to the fire there be  however this difference that some admit it more rapid as air oil and water  other more slow as stone and metal this however belong to the table of degree  no negative be here subjoin except the remark that spark be not kindle by  flint and steel or any other hard substance unless some small particle of the  stone or metal be strike off and that the air never from they by friction as  be common suppose beside the spark from the weight of the ignite substance  have a tendency to descend rather than to rise and when extinguish become a  sort of dark ash we be of opinion that here again there be no negative for we  be not acquaint with any tangible body which do not become decide warm by  friction so that the ancient feign that the God have no other mean or power of  create heat than the friction of air by rapid and violent rotation on this  point however further inquiry must be make whether body project by machine as  ball from cannon do not derive some degree of heat from meeting the air which  render they somewhat warm when they fall the air in motion rather cool than  heat as in the wind the bellows or breath when the mouth be contract the  motion however in such instance be not sufficient rapid to excite heat and be  apply to a body of air and not to its component part so that it be not  surprise that heat shall not be generate we must make a more diligent inquiry  into this instance for herb and green and moist vegetable appear to possess a  latent heat so small however as not to be perceive by the touch in single  specimen but when they be unite and confine so that their spirit can exhale  into the air and they rather warm each other their heat be at once manifest  and even flame occasional in suitable substance here too we must make a more  diligent inquiry for quicklime when sprinkle with water appear to conceive  heat either from its be collect into one point as we observe of herb when  confine or from the irritation and exasperation of the fiery spirit by water  which occasion a conflict and struggle the true reason will more ready be show  if oil be use instead of water for oil will equal tend to collect the confine  spirit but not to irritate the experiment may be make more general both by use  the ash and calcine product of different body and by pour different liquid  upon they a negative instance may be subjoin of other metal which be more soft  and soluble for leaf gold dissolve by water regius or lead by water fortis be  not warm to the touch while dissolve no more be quicksilver as far as I  remember but silver excite a slight heat and so do copper and tin yet more  plain and most of all iron and steel which excite not only a powerful heat but  a violent bubble the heat therefore appear to be occasion by the struggle  which take place when these strong dissolvent penetrate dig into and tear  asunder the part of those substance while the substance themselves resist when  however the substance yield more easy scarce any heat be excite there be no  negative instance with regard to the heat of animal except in insect as have  be observe owe to their small size for in fish as compare with land animal a  low degree rather than a deprivation of heat be observable in plant and  vegetable both as to their exudation and pith when fresh expose there be no  sensible degree of heat but in animal there be a great difference in the  degree both in particular part for the heat vary near the heart the brain and  the extremity and in the circumstance in which they be place such as violent  exercise and fever here again there be scarce a negative instance I may add  that the excrement of animal even when they be no long fresh possess evident  some effective heat as be show by their enrich the soil such liquid whether  oily or watery as be intense acrid exhibit the effect of heat by the  separation and burn of body after some little action upon they yet they be not  at first warm to the touch but they act accord to their affinity and the poor  of the substance to which they be apply for water regius dissolve gold but not  silver on the contrary water fortis dissolve silver but not gold neither of  they dissolve glass and so of the rest let spirit of wine be try on wood or  butter wax or pitch to see if this will melt they at all by their heat for the  twenty four instance show that they possess property resemble those of heat in  cause incrustation let a experiment also be make with a graduate glass or  calendar concave at the top by pour well rectify spirit of wine into the  cavity and cover it up in order that they may the better retain their heat  then observe whether their heat make the water descend spice and acrid herb be  sensible warm to the palate and still more so when take internal one shall see  therefore on what other substance they exhibit the effect of heat now sailor  tell we that when large quantity of spice be sudden open after have be shut up  for some time there be some danger of fever and inflammation to those who stir  they or take they out a experiment may therefore be make whether such spice  and herb when produce will like smoke dry fish and meat hang up over they  there be a acrid effect and a degree of penetration in cold liquid such as  vinegar and oil of vitriol as well as in warm such as oil of marjoram and the  like they have therefore a equal effect in cause animate substance to smart  and separate and consume inanimate part there be not any negative instance as  to this nor do there exist any animal pain unaccompany by the sensation of  heat there be many effect common to cold and heat however different in their  process for snowball appear to burn boy hand after a little time and cold no  less than fire preserve body from putrefaction beside both heat and cold  contract body but it be better to refer these instance and the like to the  investigation of cold XIII in the three place we must exhibit to the  understanding the instance in which that nature which be the object of our  inquiry be present in a great or less degree either by compare its increase  and decrease in the same object or its degree in different object for since  the from of a thing be its very essence and the thing only differ from its  from as the apparent from the actual object or the exterior from the interior  or that which be consider with relation to man from that which be consider  with relation to the universe it necessary follow that no nature can be  consider a real from which do not uniform diminish and increase with the give  nature we be wont to call this our table of degree or comparative instance