128 



DR. PARRY S REPORT. 



4 



Our route hence to the Colorado river leaves this depressed alluvial tract to the souths and 

 passes again over the hard, gravelly surface of the desert table-land till we come npon the 

 regular wooded hottoms of the main river. These hottom-grounds are everywhere bounded by 



a distinct line of the desert table-land, which forms bluffs 

 of greater or less height. The character of these bluffs 

 is often obscured by drifting sand-^ which is constantly 

 encroaching on the lower tracts. 



This npper bottom-land is densely wooded with mez- 

 quitCj which here finds its most congenial soil, and 

 spreads its thorny branches on all sides, forming im- 

 penetrable thickets. To this higher level succeeds a 

 lower surface of moist soil, supporting cotton-wood and 

 willow, both of which extend 



to the immediate edges 







n 



<- -= 



/ - . .— ^ 



^> 



of the stream. 



In passing up the river on its right bank to the junc- 

 tion of the Gila, w^e encounter a rocky ridge abutting 

 directly on the river bank : thence rising inland into 



^^ Pilot Knob" range. 



high rngged peaks, it forms the 



The character of the rock, as exposed on the river bank, 



IS gneiss 



having a distinct 



laminated structure. This 





TO 





to 

 CO 



— to 



o 



c 



"p. 



too 



a 



h4 





CJ S c^ 



.a rt 



O 



character gradually passes into a form of sienite, com- 

 posing the principal mass of the adjoining mountain 

 ridge. 



The immediate junction of the Gila and Colorado 

 rivers is marked by a formation different from any else- 

 where noticed. It consists of rounded knolls, which rise 

 from fifty to one hundred and fifty feet above the river 

 level, and are strewn over with the erratic deposites 



Its internal struc- 

 ture is thus in a great measure concealed. In the cleft 

 made by the passage of the Colorado, just below the 

 iti junction, the central nucleus is brought to view, and ex- 

 hibits a form of epidote rock, occurring as an irregular 

 breccia, and showing evidence of internal disturbance 



93 





to 



***** 



O 'TtO 



2 



H 



o 



u, CJ O 



belonging to the desert formation. 



below. 





— © f- 9 



« ."^^-^^-^ 



^ c; ^ s. > "SJ 



o 



C cj bf ^ 3 t* •-> rt 



The Colorado river, below the junction, is barely five 

 hundred feet across. The Gila, near its mouth, is one 

 hundred and fifty feet wide. The depth of channel in each 



isll"'^^ is very variable. 



The alluvial delta lying north of the junction of these 



two rivers is considerably below high- water mark. 



It 



H^ P 



^ 5 3 5 2^ 



o c :: — V, ^ ■- 



■g rt o § "^ ^ C 



o'c^ ^y— .-r £ o 



c; . .d - . . 



thus furnishes soil suitable for cultivation, and is occu- 

 pied as such by the Yumas Indians. Some two miles 

 above the junction, on the right bank of the Colorado, 

 are marks of an old river bed, which, in the time of 

 floods, is filled with an obstructed body of water, forming 

 frequent sloughs and 



lagoons along 



its course. 



The 



