GEOLOGY. 325 



gas currents, and on the formation of Eock-salt nests. This distinguished 

 geologist concludes, from observation, that the carbonic acid gas is formed 

 without elevation of temperature in the dolomitic strata of the saliferous 

 deposits, including gypsum and rock-salt, and that silica combined with 

 alkalies must be operative in separating a carbonic acid from its combina- 

 tion with lime and magnesia. M. Schiibler ordered experiments to be made 

 for the confirmation of this theory. Phials filled with a pulverized mixture 

 of gypsum, dolomite, quartz, and rock-salt, and placed with the orifice 

 downwards in glasses filled with mercury, to exclude the ingress of the 

 surrounding air, were sunk in bored holes to the depth of 500 to 600 feet ; 

 care had been taken to expel every vestige of atmospheric air by exposing 

 the phials so prepared to a temperature of 100. Eight days after the com- 

 mencement of the experiment the phials were again taken out, and the pul- 

 verised mixture in them was analysed. It contained bicarbonate of lime, 

 and a substance similar to dolomite in hardness and its resistance to the 

 action of acids. The vacated portion of the phials was filled with gaseous 

 carbonic acid. 



AKTESIAX WELLS OX THE PLAINS. 



With a view of facilitating the overland intercourse with California, the 

 War Department some two years since despatched Captain Pope, of the 

 Engineers, with a party, to endeavor to procure water by means of Artesian 

 wells on the great plain of Llano Estacado, on the thirty-second parallel of 

 latitude, between ISTew Mexico and the Mesilla Yalley. 



Captain Pope went out to the scene of his labors in the spring of 1855, from 

 Indianola, by the way of San Antonio, and formed his camp on the banks of 

 the Pecos river, where it is intersected by the thirty-second parallel of latitude. 

 From this point he proceeded with his working parties due east a distance of 

 fifteen miles, and there sunk the first well. From the Pecos river the country 

 seems to the eye to be a perfect level, but instrumental observation shows 

 that there is a rise of about six hundred feet in a distance of thirty-five miles ; 

 and from that point, which may be termed the summit of the plain, it con- 

 tinues with a gradual descent eastwardly, to the hills from which run the 

 head waters of several of the forks of the Colorado river. 



In sinking the wells Captain Pope found no difficulties in th,e geological 

 formation. This is entirely composed of alternate strata of indurated clay 

 and cretaceous marls, of every variety of color, easily bored through, but 

 sufficiently hard to prevent the walls of the boring from falling and incom- 

 moding the labor. 



The first stream of water was struck at a distance of three hundred and 

 sixty feet, and it rose to a height of seventy feet in the tubing. Continuing 

 the labor through the same formation, the second stream of water was struck 

 at the depth of six hundred and forty-one feet, which rose four hundred feet 

 in the weh 1 , or about fifty feet higher than the first stream. These labors 

 demonstrated the existence of water streams beneath the surface, but as winter 

 was approaching, and the material which he had brought having been exhausted, 

 Captain Pope went into winter quarters on the banks of the Rio Grande. 



