Page:Collier's New Encyclopedia v. 09.djvu/340

LEFT TEMPERANCE MOVEMENT 288 TEMPERATURE facture and sale of liqnor after Jan. 16, 1920. TEMPERATURE, the thermal condi- tion of a body which determines the in- terchange of heat between it and other bodies. Our first ideas of temperature are derived from our sensations of hot and cold. The effect of adding heat to a body is to make it hotter, unless it is at its melting or boiling point. This rise of temperature is accompanied by volume changes, on which all our prac- tical methods of measuring temperature depends. Now, though the idea of tem- perature is familiar enough, its true sig- nificance is difficult to understand. So- called thermometric measurements of temperature are not measurements in the strict scientific sense of the term. They are simply the comparison of cer- tain other effects which accompany change of temperature in special bodies. A scientific measure of temperature should be independent of any particular substance, and should depend solely on the fundamental properties of heat it- self. This absolute measure of tempera- ture was first given by Lord Kelvin (Sir "W. Thomson), who based his system on Carnot's thermodynamic cycle. The ki- netic theory of gases has given us a definition of temperature in terms of the kinetic energies of the molecules. The as- sumption is that the molecules are free from molecular forces; the conclusion is in agreement with Boyle's, Gay-Lussac's, and Charles's laws. As no gas obeys these laws rigorously, the inference is that intermolecular actions come into play, so that only part of the tempera- ture can be expressed in terms of the kinetic energies of the molecules. The eame is true, but in a much greater de- gree, for liquids and solids, for which as yet no kinetic theory has been formu- lated. From experiments made by Kelvin and Joule, the absolute zero of temperature was found to be 274 centigrade degrees below the freezing point of water, or — 461° F. This agrees almost exactly with the value deduced from the kinetic theory of gases. From our present standpoint, therefore, we cannot expect to get a cold- er temperature. The coldest natural tem- perature hitherto registered on the earth's surface is — 88.8° F., which was observed in January, 1886, at Verkhoyansk in Siberia (lat. 67° 34' N. and Ion. 133° 51' E.). Olszewski has, in his experiments on the liquefaction of the gases, meas- ured temperatures as low as — 373° F. by means of a hydrogen thermometer. Guesses have been made from time to time as to the temperature of space. Pouillet, for example, putting it at — 238* F. and Fourier at — 58°. From our pres- ent physical outlook, however, the phrase "temperature of space" is meaningless. Only where matter is can a true tempera- ture exist. In meteorology the distribution of at- mospheric temperature is one of the most important problems calling for discus- sion. The mean annual temperature over the whole surface of land and sea is perhaps about 45° F. At Verkhoyansk the lowest monthly mean averages — 61.2° F. The highest monthly mean averaged over several years may be set down at fully 110° F., and is experienced in the N. W. parts of India, where the ther- mometer in free shaded air not unfre- quently touches 125° F. Loomis in his "Meteorology" gives 133° F. as the high- est authentic reading, made in the Great Desert of Africa. To facilitate the study of the distribution of temperature at the earth's surface, it is usual to construct charts of isotherms. These are lines, each of which is drawn through all places having the same mean monthly, mean seasonal or mean annual temperature. The periodic changes of atmospheric temperature are due to the sun. The earth itself has, however, a distinct tem- perature, which increases at the rate of 1° F. for every 50 or 60 feet of descent through the few miles of crust accessible to us. On this real earth temperature the mean annual temperature of the air must to a large extent depend. TEMPERATURE OF THE BODY. The terms cold-blooded and warm-blooded animals serve roughly to indicate, the former, those animals which possess a temperature little raised above that of the surrounding medium; the latter, those with one considerably higher. Fishes, frogs, and reptiles are cold-blood- ed animals, while birds and quadrupeds are warm-blooded. Heat is produced through the combination of the oxygen of the atmosphere with the carbon and hy- drogen of the blood and tissues. A much larger quantity of carbon and hydrogen is added to the blood from the food than the ordinary nutrition of the body de- mands; and the oxygen inhaled from the atmosphere, uniting with these ele- ments, produces heat, carbonic acid, and water — the latter products representing the ashes of the bodily fire. Thus the temperature of the living body depends on chemical change. It is produced by the oxidation of combustible materials derived from the tissues and from the blood. The quantity of carbon and hy- drogen which in any given period unite with oxygen in the body, may be ac-