4 

 1 



Ex. Doc. No 41. 51 



leave the valley scarcely a mile wide. The cottonwood,. however, 

 is getting'more plentiful, and we have not been obliged to use the 

 *'bors de vache" in cooking for some_days. 



To-night I measured two sets, or IS lunar distances, east and west 

 «, 1^ altitudes of polaris, 10 of andromedffij and 8 of alpha lyrte 



The resulting latitude 34" 07' 39". 



Longitude Ih. 07m. 645. . . 



October 5. — Camp near Secoro. — Last night a Mexican came into 

 camp, and said we should now leave the river and strike for the 

 Gila, nearly due west. He was one of the men engaged by me as 

 guide while on the first trip to Tome. We accordingly moved only 

 six miles to-day, and encamped a little north of Secoro, preparato- 

 ry to taking the hills to-morrow. The prospect is forbidding; from 

 the Sierra Lescadron, opposite the amphitheatre, as far south as the 

 eye can reach on the western side of the river, is a chain of precip- 

 itous basaltic mountains, traversed by dykes of trap. Through 



ass 



I rode to the base of the Sierra Secoro, overhanging the town of 

 that name, and about three miles distant from the river. It is a 

 confused mass of volcanic rocks, traversed by walls of a reddish 

 colored basalt and seams of porphyritic lava and metamorphic sand 

 stone. In- one or two places, where the water had washed away the 

 soil near the base, I found specimens of galena and copper ore very 

 pure; but of the extent of these beds I can form no opinion, nor 

 can I say positively they were not erratic. The ore in 'this moun- 

 tain is said at one time to have been worked for gold, but the diffi- 

 culty of getting quicksilver induced the operator to move to a mine 

 ■on the opposite side of the river, near Manzanas, where, it is said, 

 ^quicksilver is to be found; but tlie specimens from that place, of 

 what th6 inhabitants exhibited as rock containing quicksilver, on 

 analysis, was found to contain none. Should the command halt to- 

 morrow to prepare for' the mountains, I shall be enabled togive'the 

 place a more thorough examination. 



To the east, close to the banks of the river, still runs the Sierra 

 Grande, which commences at Zandia with such towering heights 

 but here tapers down to moderate sized hills. The formation is 

 apparently of different colored sand stone, and wherever the strati- 

 fication shows itself, dipping about 25 degrees to the south and east; 

 but in some plac>^s it is horizontal, and in others showing great dis- 

 turbance. With the glass may be seen walls of light-colored stone, 

 basalt or trap, running off for miles in a straight line nearly north 

 and south. ^ The town of Secoro, containing about one hundred in- 

 habitant^, is prettily situated in the valley of the river which is 

 here almost circular, and about three or five miles in diameter. 

 The church, as usual, forms the salient point, which meets the eye 

 at a great distance. 



The growth on the sanJ plains to-day was chiefly iodeodonda* 



* - — -T-^- I - _ J .J .._... ... _ - - _.. _ 



Since writinjr the above, the fonowing extract of a note from Dr, Torrey wa.-? received 

 in reference to this plant, which is so i-emarkahle, and extends over so great a surface. # 



The iodeodonda I find described in a late work by Moricandj entitled ^Plantes nouveUes 

 Ott Tares d^j^mcriquc' It is described by him as a new genu?, under the name larrea. It is 



veil figmed in his 48th plate as Larrea Mexicana, In its affinities it 13 allied to guiacum." 



._x 



