CLIMATE OF THE SANTA CATALINA MOUNTAINS. 53 
exactly the same days covered by the Marshall Gulch record), and 
14.86 inches at the mountain station. The general correspondence 
between the dates of heavier rains at these stations, 5,000 vertical 
feet apart, indicates the close relationship of the atmospheric factors 
which determine the rainfall of all altitudes. 
TaBLE 5.—Comparative daily incidence of rainfall at the Desert Laboratory (2,663 feet) and 
at the Montane Garden in Marshall Gulch (7,600 feet), for June, July, and August 1911. 
June. July. August. June. July. August. 
Day of Day of 
month. month. 
D.L.|M.G D. L.| M.G.| D. L.| M. G. D.L.|M.G,) D. L.| M. G.| D. L.} M.G 
TBts silo ee alad we -98 | 4.03 |.....)...... gs | an eee ener? -19 | 1.96 | .52 |...... 
QO coves a seadeies pan) ere errs erro ABE licesael ea es Ay | detalii aavreallhe se anece 
eis cl eva. aut Ihenacheanelticacneatell oasere Ste | emuasall Maemennen TOT. ale meallas sam zz -62 | .46 ]...... 
AED cine ck eave lacs ad 5 callsutee ail] 8g 5aa-9 lente gweaeiogs QOUB. lecevuleaans MOS Varennes .53 .61 
Sted cdcoas [y cosialvd ear leserce alneakeel adadces Wes lecaccleawnd .21 .14 | .76 -10 
Gibhias ay bows ove cei ohe awa weeeek ewes DO De eal brssidearch| Sie conten [tars acene |e yess -88 | 2.60 
Ttbiscelicae sc |acivreas a rar T sesaee DBM all sicrdcaiselhshincw tive oratavera’y Watsteudpe| oceans 64 
Stick xis cP eocealbcase MOS |ewaue AS |) SAMs sl cceeulesacalsccwe ee are ere ne 
Otho |e eroslasaxs DT Weewekaliaaas. 287 || 2oths. clic ices MOD bicaccshis ee sla xe eee 
10th. EP. ladwes PAO qi cieeessaleceulial| VA wae 26thin.l sexs efuo wen .33 pr OS Meare arte 
11th ol | .25| T 5 Tal es Ga eer Dit hiss lisse scien levauers ce) lis wes eerste 
LD Gha ss | FE | Sekai recs el here.0'g2e: al tiomaatdigte & atats Sethi. dn ws omnes ee pe Bloee sheital| bs wae | cous Na ah 
13th...) T |; .42] T |...... 10 esves 29thie cD! Wsicess| eewoloedaael easy al aaa 
14th..| T det) Lo Pos ckeelieedelbeeces SOth is) LD) ieelsesvciaaillantaioaieltas 4 lowaaain 
Tcshiwaadlicess AD fess cesliwawel se di-a8 wi Sbscalewnae aver deoseeluesewaly aaa al ennrwe 
L6thiyeliseealeaaiallaces’s G84 ewes | eee eas 
Total rainfall: Desert Laboratory, 5.42 in.; Montane Garden, 14.86 in. Total number of 
rainy days: Desert Laboratory, 15 (or 31, including days with T); Montane Garden, 19. 
Another comparison which it is possible to institute between the 
summit of the Santa Catalinas and the desert is the summer rainfall 
totals from 1907 to 1914 inclusive (see fig. 9). The directions of the 
curves which show the march of the summer precipitation from year 
to year indicate an almost complete lack of relationship between the 
mountain and the plain. It is obvious that the curve of altitudinal 
increase of rainfall determined in such a year as 1910 would be very 
unlike the curve determined in 1911. 
It has been suggested by Smith * that there may be a relative 
increase of rainfall at the higher altitudes as the summer advances, 
which is to say that the gradient of increase of rainfall with altitude is 
steeper for the late summer than it is for the early summer. In order 
to test this possibility the series of ten readings taken in the humid mid- 
summer of 1911 and the one set taken in the early arid after-summer 
have been grouped into totals for five periods of approximately one 
month each (table 6). An inspection of the table shows that the maxi- 
mum rainfall occurred between July 18 and August 24 at 3,000, 4,000, 
* Smith, G. E. P. Groundwater Supply and Irrigation in the Rillito Valley. Ariz. Agric. 
Exper. Sta. Bull. 64, 1910. 
