PASS OF THE CRUZ DEL MARQUES. 179 



and sand which cover a great portion of the porphyritic 

 trap and basalt composing the cordillera issued forth. 



From my passing observations I should suppose that 

 some of these craters have ejected water as well as fire ; 

 and particularly the cone which the traveller leaves to 

 the right in traversing the ridge. It has evidently thrown 

 its lavas on both directions ; and report says, that one 

 immense stream proceeding from it, or from a neighbour- 

 ing cone of the Ajusco chain, may be traced down the 

 successive steps of the table land to the very shore of the 

 Pacific. 



In process of time we reached the Cruz del Marques,* 

 a solid stone cross erected by Cortez, to indicate the 

 bounds of the territory assigned to him by Montezuma. 



The shade of the pine forest, which still clothes a great 

 part of the upper region of the mountain, was grateful 

 to us ; at the same time that it was the most perilous 

 part of our voyage, so far as the probability of our being 

 robbed went. We passed, however, without molesta- 

 tion, retaining possession of our watches and purses, and 

 the cherished opinion of our being invincible. 



If, in quitting the valley of Mexico at daybreak, we 

 had to complain of the cold, noon brought with it a de- 

 gree of heat for which we were quite unprepared, and it 

 grew in intensity as we descended the steep face of the 

 mountain to the southward. The western slopes of the 

 cordillera of Mexico are far more sudden and inclined 

 than those on the side of the gulf, and the consequence 

 is, that by the route we were now following, after a jour- 

 ney of a few hours' travel, you descend to a level, to 

 reach which, on the opposite side, you must travel for 

 several days. 



We had not descended far upon the southwestern 

 slope, before we descried the sea of broad and yellow 

 plain, which here formed the second step of the table 



* About 9,500 feet above the sea. 



