Arizona republican., 1908-04-01

tlcularfy those m the Salt River valley,
 were higher than the readings made in the middle west. yet the sensible. or wet bulb. temperature readings of i Phoenix at the same time. showed a much greater decrease than those
 made in the middle west
 The minimum temperature readings made on January l5. 1905. during the passage of a cold wave over the middle west present an interesting study. It may be noted that at several places minimum readings below zero and maximum readings far below the | freezing point were recorded, while in the Salt River valley the readings of both maximum and minimum ther
 mometers, t66 degrees and 49 degrees respectively, were considerably above
 the freezing point For instance, Chi cago recorded a ma yimum temperature of degrees above zero and mini mum temperature of 6 degrees below zero: Memphis, a maximum of 26 de- grees and Q minimum of 10 degrees; Oklahoma, maximum, l2 degrees, mini- mum. degrees below zero; St. Louis.
 maximum 10 degrees. minimum, 0; Denver. maximum, IS degrees. mini mum. s degrees.
 The winds are generally light in character. The contour of the noun tain district gives the wind direction of the Salt River valley an easterly component. In the summer months. the winds at night are from the east; : during the day they invariably blow [ from westerly direction. The great est maximum Velocities occur during ! July and August. accompanied by thunderStOrms; the least maximum ve- locities in Januar.-, February, Novem- Der and December. The highest ve- locity of the wind during the past l2 years, was AS miles per hour, from the southeast, on July 25. 1903. The ever age hourly velocity for the seasons is | as follows: spring 50 miles per hour; summer, 4.9 miles per hour: autumn, Al miles per hour: winter, 40 miles. The average monthly movement of the wind is as follows: January. 2,747 miles: February, 2.917; March, 3.650; April. 3,656: May, 3636: June. 3555; July. 3,6l4; August. 3339; September, 3,61S: october. 2.974: November. 2.597: December, 2.554. The average annual movement is 3S,057 miles. The aver age hourly movement of the wind is
 as follows: a. n., S.S miles per hour; 1 . a. m., 3.7: a. m., 3.7; 4 a. m., 3.S; 5 a. m, S.S; a. m., 3.S; a. m.. 3.9: 8 a. m, 3.9: 9 a. m., 3.s: 10 a. m., 40;
 II a. m., AZ: 12 noon, 4.6; D. m.. AS; I2 D. m.. 50: 3 D. m., 5.2; 4 D. m., 5.5; , D. m.. 5.6; D. m, 5.6; ?. m.. 5.4; Is D. m.. 4.9; 9 D. m.. 4.2; 1O D m.. SS;
 II D. m. 3.S; F midnight 3.7. The
 prevailing direction Of the wind is as
 follows: north, 6 per cent: northeast. , per cent: east, 24 per cent; south-
 east. 13 per cent; south. 6 per cent;
 southwest. per cent: west, 22 per cent; northwest. 13 per cent; calm
 per cent The average hourly velocity
 of the wind ss 45 miles per hour
 The amount of aqueous vapor pres
 ent in the air may be expressed by
 the expansive force. or pressure Gin
 inches of mercuryD. When expressed
 in terms of weight or pressure. the amount of vaDor actually present in
 the air is sometimes called the absO- lute humidity. Care should be eXer-
 cised to distinguish between the abso-
 lute humidity and the relative humid
 ity. which is commonly called humid ity. The relative humidity is the ratio of the amount of vaDor actually pres ent in the air to that which might be present at the then existing temporal ture if fully saturated. The dew point is, therefore, that temperature at which dew forms: and in order to condense moisture into dew or rain. the air temperature would have to decrease suddenly.
 To, are the most humid months of the | year; April, May, June and July are ! the driest months. The average rela- tive humidity Of spring, for the past | F years, is 8 per cent: summer. 32 | per cent: autumn. A per cent. and | winter. AZ per cent Commencing | with January. which has an average of | 90 per cent. there is a gradual decrease in the amount of water vapor in the | air during February and the spring | months until June. in which month the | determinations average 22 per cent A | rapid increase occurs in July, with an | average of 4 per cent. caused by the | advent of the seasonal summer rains ] From August to December the varia- | tions in the percentage of relative hu- | midity are exceedingly small. the form CT averaging Al per cent, the latter 46 | Der cent. Occasionally in January and | December, during rainstorms. which | are Of short duration, the humidity at- | tains maximum readings of 100 per | cent, but recedes rapidly to normal | conditions. This rarely occurs in the | remaining months of the year. From | April to August, the midday determi- | nations of humidity often read as low | as per cent.
 The averages of the night humidity, l by months. are as follows: In January, 63 per cent: February 61: March, 5S: | April, A; May. 51: June. 32; July, AS: August, 56; September, 52; October, 52; November. 58; December 60. The | averages Of the day humidity are: January. 36 per cent: February. 27: | March. 23: April. r. May, IS: June, l2' July, 2l; August, 26: September. 24; october, 27; November. 90: De- cember. 8. The greatest night hu- midity occurs in January: the least night humidity. in June. .The greatest day humidity occurs in January; the least day humidity, in June
 The average annual humidity of the I Salt River valley is given in the ap- pended table.
 Per cent Per cent 1896. 6..........44 1902. 2.......36 1897. 1903 3S i |