726 



SCIENCE. 



[N. S. Vol. XXIII. No. 503. i 



fabrics, etc., proceeded nearly as rapidly 

 as wetting. Similarly, no observations 

 were recorded on mirages or other phe- 

 nomena of refraction, of which there was a 

 notable dearth ; on a few occasions of light 

 dust da^e due to strong winds over the 

 crests and broader valleys, Sierra de la 

 Cabeza Prieta appeared magnified and 

 brought near, though its angular altitude 

 (determined by sighting over fixed points 

 in rocks adjacent to the instrument shelter) 

 did not vary perceptibly; and during the 

 entire one hundred days not a single 

 mirage of the type so common a few score 

 miles further eastward was seen. In a 

 word, the atmospheric phenomena in gen- 

 eral, like the temperature records, denoted 

 a condition of striking steadiness or sta- 

 bility during the period of observation. 



Tinajas Altas was chosen primarily as a 

 site for a study of light and its effects on 

 desert organisms; and after unsuccessful 

 efforts to obtain a satisfactory photometer 

 a series of determinations of the intensity 

 •of light by means of a simple exposure 

 meter was planned. The record is of little 

 Talue, partly because the paper used in the 

 apparatus is sensitive to moisture as well 

 as light, but in the inverse direction, so 

 that the time of coloration gave merely an 

 inseparable measure of aridity and lumin- 

 osity. In general the record indicates a 

 light intensity twice or thrice that of Saint 

 Louis— a measure probably worth less than 

 the common experience of photographers 

 that in the arid region given plates ordi- 

 narily require but one half to one fifth of 

 the exposure needed in humid regions. 



COMPARISONS. 



Tinajas Altas was selected as a desert 

 station, yet the records were found notably 

 discordant with incidental recollections of 

 and notes on climate in the more desert dis- 

 tricts of Nevada, southern-central Arizona 

 and central Sonora. The absolute and 



mean maximum temperatures were de- 

 cidedly lower and the diurnal thermometric 

 range much lower, while the mean tem- 

 perature was rather higher and the abso- 

 lute and mean minima much higher than 

 anticipated; eoncordantly, the moisture 

 (dew-point and relative humidity) was 

 both higher and much less variable than 

 previous experiences indicated as probable 

 or even possible — it is, indeed, a striking 

 fact that the entire range of relative 

 humidity during a period of one hundred 

 days should be no more than 71 per cent., 

 and it is even more striking that, despite 

 the considerable average humidity, the 

 dew-point was never reached during the 

 one hundred-day period. In short, while 

 Sierra Gila and the adjacent plains are 

 typical if not utter deserts, the climate of 

 Tinajas Altas impresses the observer as 

 subhumid rather than arid— and this de- 

 spite the limited precipitation. 



As the record assumed form during July 

 and August, definite comparisons were 

 made with other stations in Arizona, espe- 

 cially with the cooperative (until recently 

 known as volunteer) stations in the western 

 division of the territory; this being made 

 easy through the monthly records issued by 

 the 'Arizona section of the climate and 

 crop service of the Weather Bureau' pub- 

 lished by authority of the Secretary of 

 Agriculture, under the direction of the 

 chief of the "Weather Bureau, by Lewis N. 

 Jesunofsky, section director. Contrary to 

 a widespread impression (first produced 

 when Fort Tuma was the sole station in its 

 region), these reports show that Tuma is 

 (at least during summer) by no means the 

 hottest station in the country— indeed, with 

 the single exception of the mountain sta- 

 tion Kingman, its temperature is both 

 lower and more equable than that of any 

 other station in western Arizona: Aztec, 

 Mohave, Mohawk, Parker and Sentinel, 

 with several other points in the southern 



