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anywhere inside the artesian well area or east of the catchment area. When locating a site for an artesian well it is necessary to know that it is lower in elevation than the catchment area or source of the water; that the water-bearing rock extends beneath it, and that there are impervious layers of rock between the surface and the source of the water. The catchment area is the area of the exposure of the water-bearing sand. This sand is occupied by the eastern border of the Upper Cross Timbers from the Colorado to Red river. Everywhere east of this line in the artesian well area the bed of water-bearing sand passes downward to the southeast beneath the hard limestone occurring between the Upper and Lower Cross Timbers north of the Brazos river and between the Upper Cross Timbers and the black waxy land in the district between the Brazos and Colorado rivers. Along the eastern border of the hard limestone area artesian water can be gotten at depths varying from 600 to 900 feet. West of the International and Great Northern depots in Georgetown and Round Rock it is not needed to bore more than about 600 feet for artesian water.
There are many points in the hard limestone area that are above. the source of the artesian water, and unless the location is in the valley of one of the principal streams it is best to know the elevation compared to the elevation of the source of the water before proceeding to make an artesian well.
IRRIGATION.
Examinations were made wherever it was thought practicable that lands could be irrigated, and while it is not considered possible to irrigate any great extent of area by a single spring or well, there are many places at which gardens and small farms may be irrigated by them at comparatively little cost. A seventeen acre tract of land on the San Gabriel river, eight miles above Georgetown, is irrigated by a spring at no cost except ditching.
Irrigation may be done in a similar manner on a small scale by means of storage reservoirs, constructed by building dams across the valleys of small streams. The rivers and creeks of this region are streams of erosion, having narrow flood basins with terraces of its former deposits bordering them. In these valleys there are sufficient quantities of the most fertile lands to require all the water afforded by the streams to irrigate them. Along the south side of the San Gabriel valley for four miles above the Williamson-Milam county line, there are not less than 2000 acres that can be successfully irrigated by damming the river, provided that it will afford sufficient water for so large a tract.
Respectfully,
J. A. TAFF,
Assistant Geologist.