Temperature

“ The temperature of our earth being very near to that at which water becomes solid, and reciprocally changes from solid to fluid, and as this phenomenon takes place frequently under our observation, it has very naturally followed, that, in the languages of at least every climate subjected to any degree of winter, a term has been used for signifying water in the state of solidity, when deprived of its caloric. ”

“ The temperature of man is about 98°, (Fahrenheit’s thermometer,) and that of some other animals is higher; the temperature of birds, for example, is about 110°. It is obvious, that in most parts of the globe, the heat of the atmosphere is, even in summer, less than that of the human body. In our latitude, the mercury rarely attains 98°, and sometimes it descends to several degrees below zero. ”

“ Our great luminary emits an incessant flood of radiant heat in all directions. A minute fraction of that heat is intercepted by our earth, and is, directly or indirectly, the source of all life, and of nearly all movement, on our earth. To pour forth heat as the sun does, it is necessary that his temperature [Pg 516] be enormously high. And there are some facts which permit us to form an estimate of what that temperature must actually be. ”

“ Every substance radiates its heat, and receives in return a portion of that emitted from surrounding bodies. If two bodies of unequal temperature be placed near each other, the warmer of the two will radiate a portion of its heat to the colder, and will receive some of the heat of the latter in return; but as the warmer body will emit more heat than it will receive, the result will be, that after a time, the length of which will depend on the nature of the bodies, both will acquire the same temperature. ”

“ Air may be brought below the normal temperature due the height at which it may be, by radiation and other processes. It may also be raised above that normal temperature by the setting free there of the latent heat of vapour or by the action of the solar ray upon the cloud stratum. ”

“ The unit of temperature is a degree, a measured part of the expansion which a column of mercury within a tube undergoes when heated from the melting point of ice to the boiling point of water at sea level. ”

“ The interior temperature to which the earth is subjected arises from three different sources, namely, from sidereal heat, from atmospherical heat, acting either by radiation or by contact, and from solar heat. ”

“ Study carefully, as in the previous problems, the relation of the different types of temperature distribution in the atmosphere to the weather conditions as shown on the daily weather maps.
Observations made in different parts of the world, on mountains and in balloons, have shown that on the average the temperature decreases from the earth’s surface upwards at the rate of about 1° in 300 feet of ascent. The rate of vertical decrease of temperature is known in meteorology as the vertical temperature gradient. ”

“ When the air is dry evaporation is very rapid, but as it becomes more and more filled with moisture the evaporation is checked to the same degree. This fact accounts for the difference of bodily comfort that we experience at different times in the year when the temperature is the same. Sometimes we are very uncomfortable although [Pg 63] the temperature is not above 75 degrees Fahrenheit, more so even than we are at other times when the temperature is ten or fifteen degrees higher. ”

“ Observation shows that when the quantity of vapour in the air is great, and also when the relative humidity is high, temperature falls little during the night, even though the sky be perfectly clear ; but when the quantity of vapour is small, or the relative humidity is low, temperature rapidly falls. On the other hand, during the day the temperature rises slowly, when the quantity of vapour is great, or relative humidity high, even though the sky be clear, but when the quantity of vapour is small, and humidity low, temperature rapidly rises. ”

“ When the air has passed over cold countries, it will probably arrive here at a temperature much below our own, and then it must absorb heat from every object it meets with, which will produce a general fall of temperature. ”

“ I should imagine the temperature to be about 120 degrees. Most people, I think, take a rather childish pleasure in watching the first stages of the manufacture of familiar products. I confess to feeling interested on being told that the stream of muddy liquid issuing from the crushed canes and trickling gaily down its wooden gutters, would ultimately figure as the lump-sugar of our breakfast-tables. ”

“ Thus, as summer advances, the approach of the sun to a vertical position tends to produce a constant increase of temperature; but with this effect of a constant cause, there are blended the effects of many variable causes, winds, clouds, evaporation, electric agencies and the like, so that the temperature of any given day depends in part on these fleeting causes, and only in part on the constant cause. ”

“ On the other hand, radiant heat passes easily through the air, strikes the thermometer, and raises its temperature quite independently of the influence of the air whose temperature we wish to measure. ”

“ 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. ”

“ This equalization of temperature, moreover, takes place much more rapidly, than it would do in a solid body; hence alternations of heat and cold, as day and night, summer and winter, produce in water, inequalities of temperature much smaller than those which occur in a solid body. ”

“ Because the temperature of our climate differs more from the temperature of the torrid zones in the winter than it does in the summer, and the inequalities of temperature cause frequent changes in the degree of prevailing heat. ”

“ Check instruments. Humidity is so readily affected by temperature, wind, and pressure, that a knowledge of these factors is essential to an understanding of its fluctuations. Pressure, disregarding daily variation, is taken account of in the tables for ascertaining relative humidity, and is determined once for all when the altitude of a station has been carefully established. The temperature is obtained directly from the dry bulb reading. ”

“ As the quantity of moisture in the atmosphere increases with the temperature, this element, which is so important for the whole organic creation, must vary with the hours of the day, the seasons of the year, and the differences in latitude and elevation. ”

“ 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. ”

“ No feats of discovery, not even the search for the North Pole or Stanley's expeditions in the heart of Africa, present more points of fascinating interest than the attempts now being made by scientists to explore the extreme limits of temperature. We live in a very narrow zone in what may be called the great world of heat. The cut on the opposite page represents an imaginary thermometer showing a few of the important temperature points between the depths of the coldest cold and the heights of the hottest heat—a stretch of some 10,461 degrees. ”

“ When air holds all the moisture it can sustain, its moisture is said to be at 100 per cent.; when it holds only one-half as much as its temperature demands, it is said to be at 50 per cent.; and when it holds three-fourths of what its temperature requires, it is at 75 per cent. ”

“ 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. ”

“ For mental activity the temperature is much lower than for physical, being an average of approximately 40°. In other words, people’s minds are most alert and inventive when the temperature falls to about freezing at night and rises to 45° or 50° by day.”—Huntington and Cushing’s Human Geography. ”

“ The temperature of the whole body is lowered, but not to the freezing point. The diminution of heat, as you know, produces a contraction in the bulk of fluids, as well as of solids. This effect, however, does not take place in water below the temperature of 40 degrees, which is 8 degrees above the freezing point. ”

“ B. Those parts of the earth which are once heated, retain the heat for some length of time, and the additional heat they receive, occasions an elevation of temperature, although the days begin to shorten, and the sun's rays to fall more obliquely. For the same reason, we have generally more heat at three o'clock in the afternoon, than at twelve, when the sun is on the meridian. ”

“ This points to a chief acting force on which the great movements of the atmosphere depend, viz., simultaneous local irregularities in the distribution of temperature in the atmosphere. The local expansion of the atmosphere by heat during the day is greatest over land, where the air is clear, dry, and comparatively calm, and least over the ocean, where the sky is clouded, and the air loaded with moisture. ”

“ If a dry atmosphere is of uniform temperature and pressure at various levels, but has a vertical temperature gradient a little greater than the normal cooling of an ascending gas, a portion of air started upward in any casual way becomes warmer than its lateral environment, and hence continues to rise until the unstable condition due to abnormal temperature gradient ceases. ”

“ What we do find, in exact conformity with obvious physical principles, is that in the hemisphere where the water surface largely predominates over that of land, the temperature is much more uniform than where the land occupies the larger portion of the surface. In the former, the heat of summer is mainly expended in the work of converting water into vapour, and partially restored in winter in the conversion of vapour into water or ice. ”

“ The natural temperature of the human body is 98·4°F. and the little arrow on the thermometer indicates this normal degree of heat, so that when the index rests at the arrow, the natural temperature is proved to be present. ”

“ The moment we shoot above the clouds we are in the sunshine, with the sea of clouds below us. Our thermometer is placed in the shade, so that the direct rays of the sun cannot reach it, as we wish to know the temperature of the surrounding air. ”

“ In descending from the surface of the earth, to depths continually augmenting, the mean temperature of the year augments gradually; yet, immediately below the surface, and at depths of half a foot or a foot, the mean temperature is found to be a minimum.
2. The rate at which the annual variations of temperature are transmitted to the interior of the earth, may be estimated at 6 or 7 days for 1 foot thickness of earth. ”

“ We have already said that so long as the air remains in a uniform condition as to temperature it will absorb moisture in a transparent state until it is filled to the measure of its capacity at a given temperature. ”

“ I allude to the wind as the obstacle to our exercise; for temperature, when the air is still, is no bar to any reasonable amount of it. Three or four coveys of ptarmigan have been seen, and of these I shot one brace. The cold increases: thermometer has fallen to -471⁄2°, although blowing a moderate gale at the time, and the atmosphere dense with mist. ”

“ 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. ”

“ As respects the first, it has been discovered that, when underground temperatures are examined, so that local and temporary causes of change are eliminated, there is a recognizable diminution of temperature in years when spots are most frequent. ”

“ Every spot is surrounded by a more or less bright, luminous cloud. I do not think that the spots exert any influence on the annual temperature. I register the height of the barometer and thermometer three times in the course of each day, but the annual mean numbers deduced from their observations have not hitherto indicated any appreciable connection between the temperature and the number of the spots. ”

“ This is often a more crucial factor than temperature, and one that is more troublesome to change. Relative humidity is a measure of the amount of moisture in the air as compared with the maximum amount of moisture the air can hold at a given temperature. ”

“ Arrived in the cloud-region, this vapour, being condensed, liberates the latent heat which it borrowed from the air and water below; which heat, being now set free and made sensible, raises the temperature of the surrounding air, causing it to expand and ascend still higher ”