50 GENERAL DESCRIPTION OF THE COUNTRT. 



It sometimes happens that the irrigation is protluced by natural causes — the overflow of the 

 river. This is the case in the hasin of the Presidio del Norte, and on most of the country sus- 

 ceptible of tillage in the valley of the lower Rio Bravo, Crops depending upon this mode of 

 irrigation are very uncertain, the overflows of the river being very unequal as to time and 

 extent. In some portions, however, of the Rio Bravo there are two overflows. This is the 

 case at the Presidio del Norte, below the junction of the Conchos river. The first overflow 

 occurs in June, from the melting of the snows near the head of the Eio Bravo, in latitude 3( 

 37' ; the second occurs in August, from the tropical rains which fall on the mountains near the 

 sources of the Conchos, in latitude 26° 28'. 



This occurs to a limited extent on the lower Rio Bravo, which is principally supplied in the 

 summer months by its tributaries— the Salado, the San Juan, &c. These take their rise in the 

 mountains to the south, within the regions of .tropical rains. How far the lower Rio Bravo is 

 supplied by the melting of the snows at the head of the rivcr^ I am not prepared to say ; but I 

 am inclined to the opinion that, before reachincr the tertiarv region near the mouth of the river. 



om 



In the 



intermediate portion of the Eio Bravo, that lying between Yalverde, north of which the river 



ig of the snows throughout the summer, and the Presidio del 



melti 



Conch 



nience is felt for water in years of unusual drought. I was informed, on good authority, that 



mules along the bed of the river from 



del Norte to El Paso. The bed was dry for nearly the whole distance, occasional pools of water 



ock 



It 



suffi 



animals by digging in the river-bed a few feet below the surface. 



It might be expected in this report that I should say something of the practicability of a 

 railway route to the Pacific through the newly- acquired territory ; and it was my intention to 

 do so, but the subject has been so ably and thoroughly examined and discussed by the Secretary 

 of War, and the officers of the Topographical Engineers acting under his orders, as to leave 

 nothing more to be said. All the topographical and other knowledge bearing on the subject 

 which has been acquired by the boundary survey has been freely placed at the disposal of the 

 War Department. The signal ability with which that information and the information 

 acquired by the surveys specially ordered for the purpose have been collated, leaves nothing for 

 me to say, except that our information fully sustains the conclusions of the War Office report; 

 and it is decided, beyond all question, that a practicable, and, indeed, a highly advantageous 



m the upper basin of the Rio Bravo to the vallev of 



territory. 



It has already been stated, as one of the facts elicited by this and previous surveys, that if 



from the Gulf 



Gulf of Mexico, near the parallel of 32°^ and that north of that parallel no good road even for 

 wagons could be found, uniting the valleys of the Bravo and Colorado rivers. This remarkable 

 fact was noticed by me in a reconnoissance made in 1846-47, and was first brought to the 

 notice of the government through Mr. Buchanan, then Secretary of 



State, ■who immediately 



minister in Mexico 



of latitude should be accepted. The treaty of Guadalupe Hidalgo, however, fixed a line north 



communicat 



