Arizona republican., 1908-04-01
Climatic Conditions

is that temperature which is felt at the surface of the body, notably upon the face and hands. The body is con- stantly furnishing moisture to the skin. which in cases exudes and stands in drops. commonly called precipitation.
 This moisture is evaporated by the air, hence the cooling Of the skin. This effect of cooling. by evaporation, is a safe guard against the injurious effects
 of extreme heat. The cooling of the skin subjects the body to the direct ef- feet of the sensible temperature. This | temperature is obtained from what is
 known as the whirling psychrometer. l consisting of a dry and wet bulb ther-
 mometer. each. or the wet-bulb ther-
 mometer, namel.. a thermometer
 wrapped by muslin, of fine texture.
 which is moistened by a small recep-
 tacle of pure water The dry-and wet bulb thermometers are fastened upon
 an iron frame which is whirled rapidly by means O. an attachment to the iron frame. As the instruments are whirl- ed around given space. rapid evapo- ration from the wet-bulb thermometer | ensues. During the process of whirling
 the wet-bulb thermometer is read a number oc times to note the lowest
 reading. and the lowest depths to which the mercury sinks, at the time of observation, is the temperature shown by the wet-bulb, which is the sensible temperature.
 During the summer months, maximum temperatures of 100 degrees to 110 de-
 grees are frequently recorded in the Salt River valley. which. in themselves. are far less enervating than one would suppose. owing to the safeguard which nature alone has provided by the proc ess Of rapid evaporation. The sen-
 sible temperature experienced in this section is decidedly lower than at
 points located in the east or the central
 states. If We utilize the sensible tenn peratures Of this locality. and com pare them with those of other sections. we shall find vast differences in the readings in favor of the Salt River
 valley. The readings O. the dry and
 wet bulb thermometers. as made at
 Phoenix. AriZ on July 1. 1904. at :32
 D. m.. local time, may serve as an ex-
 ample: Phoenix, Ariz.. July 4, 1905:
 Air temperature, or dry-bulb ther-
 mometer, reading. 105 degrees; wet
 bulb, or sensible temperature, reading.
 62 degrees: difference between the drybulb and wet-bulh thermometer
 readings, 43 degrees; dew point. r. de- grees; percentage of relative humidity of the air, per cent. While the air surrounding the bod. had a tempera- ture of 105 degrees. and being exceed
 ingly dry, and evaporation from the body being great. the body was sub jected to q temperature of 62 degrees only. When water is changed from the liquid to the vapor condition,
 certain quantity of heat is utilized which, upon evaporation, is changed
 10 latent, or insensible heat. A feeling of chilliness. therefore, results from the change, and as long as evaporation continues, the surface where il takes place g cooler than the general tenn perature O. the surrounding air.
 The following tabular exhibit of the average air temperature and sensible temperature readings at a select num- Der ot stations Of the L. $. Weather Bureau. for January and July. presents an interesting comparison. showing. as it does. the vast difference between the sensible temperature readings as made .n the Salt River valley and those observed in the eastern, the cen tral and the western states: