Arizona weekly enterprise., 1882-07-29
HUMIDITY OF THE ATMOSPHERE.
How ths Moisture in the Air Affects Our Comfort Under High Tenn DeYafurem.

How ths Moisture i'm the Air Affects
 Our Comfort Under High Tenn.
 peratures.
 IFrom the Philadelphia Ledser.]
 "How is it that the heat affects US less on some days with the thermome- ter at 90 degrees than on others with the mercury at 80 to 85 degrees7" This Is the question asked by a correspond ent with an observing turn of mind. We might reply to him briefly that the thermometer does not tell all the story as to the "bearability" of heat. Other things come in to ameiorate or to ag- gravate the temperature-a breeze or the quantity of moisture in the air, Relative humidity" however, as you find in the weather reports, is the great helper or the great offender. It is less comfortable on hot moist day than on hotter dry day.
 The term relative humidity" or humidity" it is true, does not refer to the absolute quantity of moisture in she air. In the language of meteorolo- gists, the term humidity" denotes the degree of its approach to saturation in the air Cor containing as much as 1t can hold). It expresses the proportion which the amount of vapor actually present in the air bears to that amount which the cir would hold if it was at the point of saturation-when dew, mist or rain is about to fall from it. When the humidity is recorded as 100, the air is completely saturated with moisture and rain is imminent, but if reported at 75 1t contains only three-fourths of the amount requisite for saturation.
 It is of great importance for those who would profit by the daily Signal Service reports to bear in mind the sig ulticance of its humidity column, es- pecially in the so-called "dog days" Lhe warmer the airis the larger becomes the quantity of invisible vapor 1t is ca pablo of sustaining and storing away in the interstices between its atoms. At the freezing point 1t can only hold one hundredth part of its own weight of in- visible vapor at the temperature of 59 deg. tue one eightieth part of its weight j; at 86 deg. onefortieth part, and for every addition of 27 deg. of temperature its capacity is doubled. If fully satu- rated at 32 deg. of temperature, it con- 'a;ns 237 grains of aqueous vapor per cubic foot; at 60 deg, 5.S7 grains in 1 each cubic foot, and at 80 deg. of the thermometer, 10S1 grains. A fall of temperature from 80 to 60 deg. throws flown, therefore, nearly five grains of water from every cubic foot of air thus chilled. A cubic foot of saturated air under average pressure and tempera- sure of 90 deg. weighs 495 grains CTroy), 3f which 146 grains are pure aqueous vapor. With the temperature verging on 100 deg, as 1t sometimes does in our ''warm waves, the atmosphere at satu- ration contains as much as nineteen and shree-fourths grains of water to the cubic bot, from which some idea may be gathered of the enormous rainfall possi- ,ilities of tropical clouds, which, heated I'D directly under the fierce sun, arc re- plete with the evaporation from equator al seas.
 At these watery particles offer resist ance to the heat of both the earth and air beneath them, which is seeking tc escape by radiation into the upper at inosphere, they thus effectually prevent the cooling of the soil and of the lowe, ,erial strata. While the "relative hu. n1idity" data in the Weather Bureaus
 bulletins do not give the absolute amount of vapor in the air, neverthe
 ess, when the percentages given art nigh, or near 100, they show that the molecules of vapor are coalescing over l,ead, and are forming with the air atoms . canopy above us, which inter
 'epts the heat of the earth in its at tempt to fly into the clouds. The vapol present also prevents the body from throwing of its surplus heat. The abili " of the human frame to bear or throw of the Il Sh cumulative temperature thu
 engendcred in our midsummer weather
 depends upon several circumstances
 Evaporation from the skin and lungs i
 perhaps the most important means tn,
 body has of reducing its surplus heat, a
 Dr. Max Won Pettenkotfer, the eminen
 Munich hygienist, has shown by the US of an apparatus for testing the quantit, of water evaporated by men and ani mals. His experience demonstrate
 that men at rest evaporate abou
 two pounds only during twenty-fou
 hours, but on day of hard work fou
 and half pounds of water. "In tn
 arst instance" he says, "about 2, 016 ca !; .oric units; in the second, 4, 480 had t leave the body in consequence of evar
 oration," and he forcibly adds "Thi l explains how it can be that even wit , the hardest work our blood will nc become warmer, but sometimes eve
 cooler, and what powerful means c cooling our body we have in the increas of our peripheric circulation and conse quent evaporation" Prof. Lortet, (
 Lyons, while ascending Mont Blan
 found that the temperature in his moutl and armpit was less than the norma : ard became normal when he was at res
 But the cooling effect of evaporation exhibited on 0 grand scale in the meteo ology of the tropics. Last year, for il
 stance, while in the high attitudes |. London and Boston the thermomett : reached or exceeded about 90 deg;
 the Island of Mauritius, lying in u : "steaming bosom" of the Indian ocea1 | within 20 deg. of the equator, the the e mometernever once rose during the ye, t over 85.6 deg, and the register show h that at the Island of Barbadoes, 12 de;
 from the equator, and in the hotte j. part of the equatorial ocean, the max
 mum temperature for the year was , deg. The greater coolness of the' tropical islands was, of course, due Il the rapid evaporation of the equatori 0 seas around them, and the fact demol
 strates more palpably than even D Il Von Pettenkofer's costly apparatl > " the hygienic value of evaporation t a the rooljno of our bodv 'sf