MAMMALS OF THE MEXICAN BOUNDARY. 29 



shallow, alkaline water. The sand wastes surrounding them are 

 covered with a white deposit intolerable to the eye. 



Crossing the divide to the west of the great San Luis Kange of 

 mountains, Cajon Bonito Creek rises in the San Luis a short distance 

 south of the Boundary. This stream, like the San Bernardino, of 

 which it is a tributary, flows to the Yaqui River. The San Bernar- 

 dino River rises in southeastern Arizona and joins the Yaqui through 

 the Bavispe River. 



Farther west, the San Pedro and Santa Cruz are the only rivers 

 worthy of mention, unless a small stream (Agua Prieta) in Sulphur 

 Spring Valley be excepted. These two are tributary to the Gila, 

 which flows into the Colorado at Yuma. 



In the Pajaritos Mountains west of Nogales there is a small stream 

 called Bear Creek, which contains fish, and flows into the Altar 

 River, in the State of Sonora, Mexico. The Sonoyta River, which 

 runs an independent course (mostly dry) to the Gulf of California, 

 also contains fish, and is the only stream of consequence between the 

 Santa Cruz and Colorado rivers. 



The Salton and Xew rivers, previously mentioned, are merely 

 temporary drains which occasionally conduct an overflow of water 

 from the Colorado River to the ancient basin of Salton Sea, west of 

 the Colorado. 



The mountains forming the Coast Range break off abruptly along 

 the Colorado Desert and Gulf of California, and, consequently, their 

 drainage is to the Pacific, The Tijuana and San Diego rivers are 

 those which reach the ocean in the vicinity — -just to the northward of 

 the Boundary. Each of these has numerous tributaries. The absence 

 of fish in them is remarkable. 



Lieutenant Gaillard has given a detailed account of all the springs 

 and wells along the boundary strip, his account being summed up in 

 the following paragraph : 



To persons luifamiliar with the deserts of the Southwest, it will doubtless 

 appear that undue prominence has been given to the question of water in the 

 preceding description of the country along the Boundary, and in refutation 

 of this idea it is necessary to call attention to the fact that supplying the 

 working parties with water on the deserts was the problem of the survey, in 

 comparison with which all other obstacles sank into insigniticance. To the 

 traveler on the desert the all-important questions are : The distance to the 

 next water, the nature of the supply, and the character of the intervening roads. 

 For while he may be able to live without food for several days, he knows that, 

 exposed to the scorching heat of sunnner, men drinking their fill at sunrise 

 frequently become crazed and in some cases perish of thirst before sunset. Nor 

 must it be forgotten that at such times so profuse is perspiration and so rapid 

 its evaporation that the quantity of water consumed by men and animals is 

 very large, averaging at one period of the Survey about 7 quarts a day for the 

 men and 20 gallous for the animals. 



