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to the Leguminosas, Rhamnacaæ, and Cactacæ, constituting the chaparral of the Mexicans. There are enormous orchards of Opuntia rafinesquei, the common prickly pear or nopal of the Mexicans, and tasajillo, Opuntia leptocaulis, is often extremely abundant. Of the Leguminosæ, the mesquite and several species of acaciæ are the most common. Lignum vita also is a common and characteristic plant. Except along the creeks, where occasionally live oaks grow, there are no trees, unless the mesquite reaches a size sufficient to entitle it to that name. Professor Bray, of the University of Texas, is making a careful study of the flora of western Texas with reference to climatic and other natural conditions. Rains are very infrequent, and the country is not capable of supporting a dense population.

The following table gives the average annual rainfall at some of the more important places, as determined by observations extending through several years:

The mean annual temperature is as follows:

January is the coldest month, but the average temperature for that month at any place is rarely as low as 45°. August and July are the hottest months, but the average for these months is rarely as high as 90°. In the summer, in the middle of the day the heat is intense, but at night there is always a refreshing breeze.

The region as a whole is underlain by a series of rock sheets belonging to the Cretaceous and Tertiary periods, which are covered to a considerable extent by surficial deposits of silt and gravel. The beds will now be described in ascending order.

The Cretaceous strata of the Texas region have been divided into two great subgroups or series, an upper and a lower. These series have been further divided into formations, which are still further subdivisible into individual strata; but for purposes of general discussion the formations are the units of the system of classification.

Climatic conditions of Texas, by Gen, A. W. Greely: Senate Ex. Doe. No. 5, Fifty-second Congress, first session.