88 FIELD CoLUMBIAN MusrEuM—GEOLoGY, VOL. i. 
plain, 7. ¢., a more or less circular valley surrounded by high moun- 
tain walls. | 
I have stated that bowlders were comparatively rare, but in the 
course of a stream crossed about a half hour’s ridé from the town 
many of considerable size were seen. ‘There were also some scattered 
over the plain, but on none of them did I notice marks of glaciation. 
Volcanic products can be seen over the portion of the plain about 
a mile east of Ameca in the form of strata of broken pumice and 
coarse ashes. These can be followed for some distance up the 
mountain. 
After a ride of about an hour the foothills, low and rounded and 
made up of alluvial soil with gravél and bowlders, were reached. 
Most of the hills were cultivated. These hills, according to Packard, 
have every appearance of being moraines, but as I have previously 
stated, they appeared to me to be rather of lacustrine origin. 
The artificial hill of Tetepetongo, previously mentioned, lies at the 
right of the road among them, rising out of a cornfield. The flora 
over these hills was far more brilliant than on the plain, probably on 
account of the greater supply of moisture. Stately yellow-flowered 
shrubs of the order of Composite, a red labiate flower and blue col- 
umbines were the most numerous among the flowering plants. Pass> 
ing these we advanced into dense woods made up of firs and cedars, 
through which the trail wound now to the right and now to the left, 
but always upward. From favorable points on the trail could be 
gained charming views of the plain continually left farther below and 
exposing ever a greater expanse to the eye. Inspiration was lent by 
the thought that the scene was but little changed from that which 
greeted the eyes of Cortes and his band as they pushed on over the 
same trail from the side of Puebla nearly four hundred years before. 
At intervals the trail skirted the brink of a deep barranca or ravine, 
that of Zumpango, which was formed by a mountain stream. The 
rock cut through by the stream appeared to be a basalt, but I did not 
approach near enough to procure any specimens. It is described by 
Felix and Lenk as differing from the prevailing andesite of the moun- 
tain in possessing a relatively large content of olivine. The amount 
of water in this and other streams crossed was naturally small, as it 
was the dry season and the only source of supply was the melting 
snow of the cone. After about two hours’ ride through woods such 
as I have described, we came out upon a series of well-marked 
plateaus which extended nearly to the cone itself. The temperature 
was here considerably colder than on the plain, and the general aspect 
was quite that of a New England pasture landin May. Long stretches 
