AND THEIR RELATION TO IRRIGATION. 
19 
and rapidly that few records are kept of the strata passed 
through, but the following, taken by J. M. Chritton, in 
Township 39 N., Range 9 E, is typical of the whole dis¬ 
trict : 
Thickness, 
Depth, 
Strata. 
feet. 
feet. Flow 
Dark, sandy loam. 
. 7. 
.. 7. 
Coarse sand and gravel... 
. 13. 
.. 20. 
Fine light-yellow sand.... 
. 22. 
.. 42. 
Yellow impervious clay... 
. 18. 
.. 60. 
Blue clay or soft slate.... 
. 98. 
..158. 
Black sand. 
. 1.. 
.. 159.... Small flow. 
Blue clav. 
. 4.. 
..163. 
Fine black sand. 
. 3. 
.. 166.... Fine flow. 
Blue clay. 
. 45. 
..211. 
Fine black sand. 
. 12. 
.. 223.... Flow. 
Blue clay.:. 
. 53. 
..276. . 
Black sand; flow so strong that with our pump we could not go deeper. 
The accompanying map show r s the extent of the 
basin, the supposed limits being indicated by the heavy 
line. These limits were fixed as the probable ones from 
the data in my possession. In some places they are quite 
exact. They were drawn before having seen the map 
given by F. M. Endlich in Hayden’s Geological Report for 
1875, where the limits of the ancient lake, there called 
Coronados Lake, are given. The artesian basin agrees so 
closelv with the boundaries of the ancient lake, that it 
ts J 
may be taken as its map. In the southeastern portion, a 
region not visited by myself, Endlich’s map shows an 
extension of the lake to the south and east around the 
mass of basalt, striking the present course of the Rio 
Grande again in Township 23. As the accompanying 
map was completed before seeing the above mentioned 
map, it was impossible to show more than a portion of 
this extension of the ancient lake bed, which is indicated 
by the dotted lines. As the limits of the ancient lake and 
the artesian basin arc practically identical for the upper 
portion of the valley, and as the same conditions which 
make the upper portion an artesian basin hold true 
for the lower, it is probable that artesian water will be 
