180 GEOLOGICAL RECONNAISSANCE OF THE DOMINICAN REPUBLIC. 



obtained at less depth. For such a test a pipe 15-centimeters in diameter 

 will be sufficient, and a strainer will be necessary if the water-bearing 

 beds are composed of fine sand. An accurate record of the strata pene- 

 trated and of the quantity and quality of water encountered at each 

 water-bearing stratum should be kept in order to obtain data for drilling 

 other wells. Samples of the water from each water-bearing stratum should 

 be collected in clean bottles that are stoppered with unused corks. Sam- 

 ples of the rocks that are penetrated should also be collected. A well of 

 this size, though large enough to furnish a test, will not be large enough to 

 supply water for irrigation. If the results of the test well are satisfactory 

 a well with a 30-centimeter casing should be drilled on high ground in the 

 vicinity of the test well. 



Although it is possible that a well 100 meters deep may obtain an artesian 

 flow, an adequate test for artesian water will require a much deeper well, 

 for failure to get water under pressure in a well at such a depth will not 

 prove that artesian flows can not be found in this region. To make an 

 adequate test for artesian water a well should be drilled to a depth of 500 

 to 700 meters unless a satisfactory supply is found at less depth or unless 

 the stratified rocks are passed through and hard crystalline or metamor- 

 phic rocks are penetrated. A site farther upstream than the experimental 

 farm — one near Guayubin, for example — would be more favorable for an 

 artesian test well. Favorable artesian structure in this neighborhood is 

 suggested by the fact that the Miocene sedimentary strata in the hills 

 south of Guayubin dip gently northward, toward the valley. The ground 

 water near Guayubin is nearer its source and is therefore probably less 

 mineralized than that farther downstream. If favorable results are ob- 

 tained from a test well sunk at this locality other deep test wells, both up 

 and downstream, would be warranted. No single well will furnish con- 

 clusive proof as to the ground water conditions throughout the region 

 around Monte Cristi, but one well properly drilled and tested will add to 

 the knowledge of the ground water conditions and will furnish data that 

 will afford more intelligent direction to further prospecting. 



