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 — arising from the rarity 
of the air, as mentioned, what can be more favorable than 
certain parts of Mexico for aaa ies 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 use 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 
| — 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 —_ tere a 
napes.) 
is however but a local na 
5. Geological - etn 
In your letter you mention a collection of rocks and m 
rals recently arrived in New York from Europe.* If well cho- 
—w collection of G. W. Featherstonhaugh, Esq. 
Vous XVI. —No. 21 
