Miscellaneous Notices, ^c. 161 



and a half degrees of Fahrenheit, and the lowest sixty-six 

 degrees. I arrived in the extreme part of the dry season, 

 the hot one, and this is now the rainy one, and the coldest ; 

 the sun nearing us every day. With this small variation of 

 temperature, in addition to the effects arising from the rarity 

 of the air, as mentioned, what can be more favorable than 

 certain parts of Mexico for consumptive patients, whose dis- 

 ease arises from overaction of the lungs, caused or increased 

 by the dense air of our country ? Besides these two advanta- 

 ges, there are others, and those of importance ; they are fruits, 

 and other esculents, of all climates, and all seasons, which the 

 extreme variableness of level above the ocean, enables this 

 country to produce, and which are produced in sufficient 

 abundance. 



4. Obsidian. 



From the fragments of obsidian which I every where find in 

 this neighborhood, on land susceptible of cultivation, it is evi- 

 dent that it was pretty extensively used by the aborigines of 

 Mexico: it was, so far as I have observed, fashioned in two 

 ways only. The most common of the instruments made of it, 

 presents a parallelogram of about two inches long and an half 

 inch in width, and in thickness two lines, more or less, at the 

 center, from whence it tapers to the longest sides, so as to 



I I ^^ ^ form two cutting edges. 



They were used for cutting, as is evident from the number I 

 find of them with their edges hacked or notched. The form of 

 the other kind is that of the common arrow or spear head 

 of our country. Many are found here, very small, much 

 more so than any I have seen belonging to the former in- 

 habitants of the United States. The most 'glassy kind of 

 obsidian was used for the former or cutting instrument : the 

 opaque, or lapideous, being the toughest, for the arrow 

 heads. None are now in use, and I should suppose, from a 

 conversation I had with a Mexican, that their use was now 

 forgotten. They are here called chinapis, (pronounced che- 

 napes.) It is however but a local name. 



5. Geological Classification. 



In your letter you mention a collection of rocks and mine- 

 rals recently arrived in New York from Europe.* If well cho- 



* The very interesting collection of G. W. Featherstonhaugh, Esq. 



Vol. XVI.— No. 1. 21 



