Fahrenheit

“ On ascending a mountain the mean annual temperature decreases on an average of one degree Fahrenheit for every three hundred and forty-nine feet. The value of fresh air and exercise is a sentiment possibly as old as humanity itself. ”

“ Dry air is cooled a degree Fahrenheit for every six hundred feet of ascent in the atmosphere. At a height of about seven miles above the earth’s surface all rising air currents have cooled to about 68° below the zero of the Fahrenheit scale, and exploration with balloons has shown that the currents rise no farther. ”

“ One of the latest wonders in practical science, is a plan for cooling the air in dwellings in hot climates; by which persons residing in India, and other oppressively warm countries, may live habitually in an atmosphere cooled down to 60 degrees Fahrenheit, or the ordinary heat of a pleasant day in England. ”

“ I shall only add, that as it has been observed here that spirits will fire by the electric spark in the summer time, without heating them, when Fahrenheit's thermometer is above 70; so when colder, if the operator puts a small flat bottle of spirits in his bosom, or a close pocket, with the spoon, some little time before he uses them, the heat of his body will communicate warmth more than sufficient for the purpose. ”

“ My personal experience has been that, to an experienced observer, dressed in furs and taking observations in calm weather, in temperatures not exceeding say 40° below zero Fahrenheit, the difficulties of the work resulting from cold alone are not serious. ”

“ All the differences in the various fabrics are due in chief part to the properties of heat. The ordinary or normal temperature of the human body is between 98 degrees and 99 degrees Fahrenheit, while that of the air will vary considerably, according to the climate and locality. Each individual, therefore, must be regarded as a material, though living, object which is enveloped in a surrounding atmosphere. ”

“ Any one who shows over ninety-nine degrees Fahrenheit is examined further for corroborative symptoms. The temperature of every one of the steerage is taken and the glass thermometer is not always cleaned as it is passed from mouth to mouth here in these crowded regions! ”

“ Fahrenheit's thermometer is the only one in use with us, I make my daily observations as early as possible in the morning & again about 4 o'clock in the afternoon, these generally showing the maxima of cold & heat in the course of 24 hours. ”

“ The Hot spring is about six miles from the Warm, is much smaller, and has been so hot as to have boiled an egg. Some believe its degree of heat to be lessened. It raises the mercury in Fahrenheit's thermometer to 112 degrees, which is fever heat. It sometimes relieves where the Warm fails. ”

“ The natural heat of the Human Body is 98 of Fahrenheit’s Thermometer—any temperature applied to it lower than 98, gives a sensation of Cold, but if the temperature applied is not below 62, the sensation of cold will not continue long, but be soon changed to a sensation of heat, and in this climate, Air, &c. applied to the living man, does not diminish the temperature of his Body, unless the temperature of it be below 62 ”

“ Alone, what did Bloom feel?
The cold of interstellar space, thousands of degrees below freezing point or the absolute zero of Fahrenheit, Centigrade or Réaumur: the incipient intimations of proximate dawn. ”

“ The thermometer (I have made some observations) falls in winter to 4 degrees Centigrade at the outside, which gives us 24 degrees Reaumur as the maximum, or otherwise 54 degrees Fahrenheit (English scale) , not more. And, as a matter of fact, we are sheltered from the north winds by the forest of Argueil on the one side, from the west winds by the St. ”

“ I am aware moisture in the air makes a great difference as affecting the human system; but a fact is a fact. The cold air from the same direction—equally charged with aqueous matter at different times—shows a difference of ten to twenty degrees in the thermometer; and yet the air at the lowest temperature affects the human system less than the highest.
"December 20th, 5.30 a.m.—Thermometer — 5°, barometer 30.200. Wind very light, N.W. Yet there must be a storm prevailing not far from us, as a tremendous roar of waters and cracking of ice comes from the direction of Davis's Straits. ”

“ On the 19th the thermometer, on this glorious fair and calm morning, was — 20°, barometer 30.175. Cold indeed; by thermometer, 52° below the freezing point. Yet so calm was the weather, that to my person it seemed no colder than at the commencement of the season, when the thermometer indicated 32° above 0. But let a smart breeze spring up coming from the N.W. then how like hot iron it will burn! The weather was such that, unless we soon had snow, the ice would freeze thick and solid throughout the regions. ”

“ Wind, as we know, is air in motion, and we feel colder on a windy than on a calm day, although the thermometer may register the same degree. Nevertheless, air is a bad conductor of heat: compare it, for instance, with water, which scalds at 150° Fahr.; whereas a man in a Turkish bath can without danger enter a room, the air of which is heated to 200°. Both air and liquids have heat imparted to them by a process called convection, in which heated particles, as they become lighter by expansion, rise, forming an upward current, while colder particles, being heavier, sink ”

“ This heat, though it produces little change on the temperature of the air which it traverses, affords us some compensation for the heat which we radiate to the heavens. At night, also, if the sky be overcast, some compensation will be made to us, both in the town and in the country, though in a less degree than during the day, as the clouds will remit towards the earth no inconsiderable quantity of heat. But on a clear night, in an open part of the country, nothing almost can be returned to us from above in place of the heat which we radiate upward. ”

“ When we came on deck on the morning of the 8th, the uniform remark of the passengers was, “What a warm day!” We had become used to a temperature of about 40°, and a rise of 5° Fahr. gave the impression of a complete change of climate. It is curious how completely relative are the impressions of heat and cold on the human body, and how difficult it is, even for persons accustomed to compare their sensations with the instrument, to form a moderately good estimate of the actual temperature. ”

“ The atmosphere, then, is heated or cooled according as it lies upon a warm or cold part of the earth’s surface; and, by means of its aqueous vapor, it serves to store up and distribute this heat, keeping the earth from such extremes of climate as would otherwise prevail.
The air lying next to a hot surface is heated; the air touching a cold surface is cooled. And upon such differences of temperature in the air the formation of winds depends.
Hot or warm air is lighter than cold air. You have learned how heat expands bodies. ”

“ Temperature and Radiation.—Very dry, clear air permits the sun’s rays to pass readily to the earth with but little perceptible loss—that is, dry, clean air is diathermous to the heat rays that impart the feeling of warmth to living bodies. [4] The heat is in turn absorbed by the earth. Earth temperature at the surface, or to a depth of an inch or two, may be many degrees higher than that of the air. Thus, in desert regions, pieces of metal lying on the ground in the sun become so hot they cannot be held in the hand. ”

“ And this equalization of temperature by means of such currents, is an operation of a much more rapid nature than the slow motion of conduction by which heat creeps through a solid body. Hence, alternations of heat and cold, [71] as day and night, summer and winter, produce in water, inequalities of temperature much smaller than those which occur in a solid body. The heat communicated is less, for transparent fluids imbibe heat very slowly; and the cold impressed on the surface is soon diffused through the mass by internal circulation. ”

“ Q. Why does wind in England generally feel cold?
A. Because a constantly changing surface comes in contact with our body, to draw off its heat.
Q. Why is a room (even without a fire) generally warmer than the open air?
A. As the air in a room is not subject to much change, it soon becomes of the same temperature as our skin, and no longer feels cold.
Q. Why do we generally feel colder out-of-doors?
A. Because the air (which surrounds us) is always changing; and as fast as one portion of air has become warmer by contact with our body, another colder portion surrounds us to absorb more heat. ”

“ Again, let the required nature be heat or cold, of such a degree as not to be sensible from its weakness. They are rendered sensible by the thermometer, as we described it above; [139] for the cold and heat are not actually perceived by the touch, but heat expands and cold contracts the air. Nor, again, is that expansion or contraction of the air in [222] itself visible, but the air when expanded depresses the water, and when contracted raises it, which is the first reduction to sight. ”

“ Our clothes, contrived to guard us from cold, guarded us from the heat on the same principles. Underneath we were surrounded with an atmosphere of air, cooled on one side to 98 deg. by being in contact with our bodies, and on the other side heated very slowly, because woollen is such a bad conductor of heat. Accordingly I found, toward the end of the first experiment, that a thermometer put under my clothes, but not in contact with my skin, sunk down to 110 deg. ”

“ If you take a red-hot ball out of a furnace and lay it down upon a frosty moor, two processes will go on—the ball will lose heat and the surrounding atmosphere will gain it. There are two ways by which you equalise the temperature of a hotter and a colder body: the one is by the hot one getting cold, and the other is by the cold one getting hot. If you are not heating the world, the world is freezing you. ”

“ Q. What is meant by “convection of hot and cold currents?”
A. The air (which is heated by the surface of the earth) ascends, warming the air through which it passes. Other air (being warmed in a similar way) also ascends, carrying heat; till all the air is made hot.
[Pg 220]
Q. Is the air made cold in a similar way?
A. Yes. The air resting on the earth is made cold by contact: this cold air makes the air above it cold; and cold currents or winds shake the whole together, till all becomes of one temperature. ”

“ That portion of the heat which results in an increase in temperature of the body is called "sensible heat," inasmuch as such a gain in heat is apparent to the physical senses of the observer. If heat were supplied to the body at a uniform rate, the temperature would rise continuously, and if the temperature were plotted against time, a smooth rising curve would result. Or, if sensible heat were abstracted from the body at a uniform rate, a time-temperature curve would again be a smooth falling curve. Such a curve is called a "cooling curve." ”

“ If one were to set down the temperature of each day, add the numbers at the end of the year, and divide the sum by 365 the quotient would equal the temperature [181] always found at that place at a depth of about thirty feet. The temperature of a deep-flowing spring is always about the mean annual air temperature of the place. Here is health-giving coolness for summer and warmth for winter of which one takes little heed and derives practically no profit. ”

“ Going out into the open air, in the temperate, and warm 324 months of the year, we often meet with bodies of warm air, which passing by us in two or three seconds, do not afford time to the most sensible thermometer to seize their temperature. Judging from my feelings only, I think they approach the ordinary heat of the human body. ”

“ Similarly air, although of the same temperature, as shown by the thermometer, will feel colder or warmer to us according to whether it is in motion or still; because when in motion it removes heat from our bodies quicker than when at rest, since more of it passes over our surface. ”

“ That this heat is furnished by the air, he proves, by finding, that that which we inspire contains more heat than that which we expire, or than the aqueous humor which we expire along with it, in a very considerable proportion; so that if the heat contained in the pure air did not become latent in the blood, it would raise its temperature higher than that of red-hot iron. ”

“ We thus see that by causing heat to pass, in the manner first indicated, from a body retained at a determinate temperature, into a body retained at an inferior temperature, we develop a certain quantity of mechanical action, which is equal to the quantity which must be consumed in order to cause the same quantity of heat to pass from a cold to a hot body, by the inverse process we have subsequently described. ”

“ Our sensations do not register the temperature of the air, but they do, in a way, register the cooling power of the air, which depends upon temperature, humidity, and air movement, and they register, especially, changes in this cooling power, for within certain limits the body soon adapts itself to a constant rate of cooling, so as to lose any impression of heat or cold. ”

“ After hot weather, a day which is not very cold, will yet feel so to us, and after cold weather we shall be ready to think a day warm, which is not so severe as the preceding. [Pg 864] In winter, a thermometer in a sitting-room enables us to regulate its heat. Too great warmth produced by a fire is injurious to health, as it relaxes the strength, and consumes the pure oxygenous air, so necessary for respiration. ”

“ The sensation of the heat on the skin is far greater than the degree of warmth indicated by the thermometer would appear to warrant, owing to the astonishing degree of reflection of the sun's rays, which is produced by the vast and naked spread of the plains, the masses of mountains by which they are surmounted, and the diminished pressure which the rarified air exerts upon the moisture given forth by the body. ”

“ As regards the mere endurance of a high temperature, the well-known experiments of Blagden, Sir Joseph Banks, and others have shown that the human body can endure for short periods a temperature of 260° F., and upwards. My own experience of furnace-work, and of Turkish baths,200 quite satisfies me that I could do a fair day’s work of six or eight hours in a temperature of 130° F., provided I were free from the encumbrances of clothing, and had access to abundance of tepid water. ”