ds of Mexico, extends above
25 deg..

There, for the reason we have been considering, it does extend further
north during July and August, in occasional showers, and in the vicinity
of Mount Picacho, Mr. Bartlett met one of its mountain thunder-storms on
the 13th of July, on his return south through Mexico, in latitude 32 deg., in
the following year. (Personal Narrative, vol. ii. p. 285). These showers
originated in strata of counter-trade, which had followed up along the
eastern side of the mountains and not from strata which had crossed them
and curved to the eastward, as is shown by the course of progression of
the showers.

Let us look, in this connection, at a fact or two of great interest,
though not directly connected with the point in hand. The southern limit
of the extra-tropical belt in winter, on the Pacific coast of North
America, is in the vicinity of San Diego, at about 32 deg.. In summer, that
limit is carried up above Astoria, which is in latitude 46 deg. 11'--about
14 deg.--yet New Mexico receives little if any rain in winter in the vicinity
of Albuquerque, but does receive a limited supply of about seven inches in
summer and autumn, five and a half inches of which falls in June, July,
and August. Albuquerque is in latitude 35 deg. 13', below the southern summer
limit of the extra-tropical belt, and north of the northern limit of the
equatorial belt. This anomaly is explained by the extension west over
northern New Mexico, of the extreme western edge of our concentrated
counter-trade, by reason of its issuing further west from the equatorial
belt in its northern extension in the summer months. This western edge, in
curving to the east, north-east of New Mexico, covers the north-western
States, Iowa, Minnesota, Wisconsin, etc., and furnishes them that great
excess of summer precipitation which is a peculiarity of their climate;
and its absence further east in winter, and the very great elevation of
the Rocky Mountains and other ranges over which their ordinary
counter-trade of that season curves, account for the absence of much
precipitation and snow there, or over the valley of the Rio Grande in New
Mexico, in winter.

We may now see, too, why the western coast and the Pacific region of the
continent, below 45 deg., are so deficient in moisture. The S. E. trades,
which arise from the western portion of the south Atlantic and the
continent of South America, which, if it were not for the Andes chain, in