190 GEOLOGICAL REPORT. [1319, 320, 321 



strata too magnesian and salty), this consideration is of especial 

 importance, and well worth a trial ; more especially as the boring 

 is generally very easy. 



It is difficult, thus far, to say, to what depth boring might require to be 

 carried ; but a few hundred feet would suffice to show what might be expected 

 within the Grand Gulf strata. So soon as, in passing through these (at Port 

 Gibson, for instance, at a depth from 500 to 800 feet) the upper, sandy strata of 

 the marine Tertiary (of the Vicksburg Group) should be reached, water would 

 be obtained almost beyond a doubt ; it would probably be somewhat limy, but 

 much less so than that of the Bluff formation, and infinitely preferable to the 

 magnesian waters in ordinary wells, of the Grand Gulf Group. It might be 

 necessary, in order to prevent the strata of the latter from contaminating the 

 water, to tube them out. The practicability of artesian wells further S., should 

 no rise of water be obtained in the strata of the Orand Gulf Group, will be simply 

 a question of depth ; in this case, the first chances at Natchez, for instance, would 

 lie between 1200 and 2000 feet ; while at greater depths, the probability of 

 obtaining artesian water would be a very strong one. But if, as is most likely, 

 water having a considerable rise should be found icithin the Grand Gulf strata, 

 the depth required might fall considerably short even of a thousand feet. 



319. c. Waters of the calcareous marine Teitiary. — All these are, 

 of course, more or less impregnated with carbonate of lime ; yet 

 not generally to such a degree as to seriously impair their fitness 

 for the ordinary household uses, nor even as strongly as those of 

 the Rotten Limestone of the Cretaceous formation. On the 

 territory of the Vicksburg Group, there is generally little difficulty 

 in regard to water : the region is hilly and much interspersed with 

 Orange Sand ridges, yielding pure water above the tertiary rocks; 

 the latter themselves contain many water-bearing strata, especially 

 in their upper portion: and the same is true of the lignitic stages 

 intervening between the several calcareous ones. The waters 

 derived from the latter are, in general, much purer than those 

 originating from either of the two principal Lignitic groups. 



320. Within the Jackson Group, water-bearing strata are 

 generally scarce, though not entirely absent. In commencing a 

 bore on the territory of the Jackson Group, we must ordinarily 

 expect to pass through their whole thickness before reaching water. 



Since, however, the dip of these strata is quite considerable, wo 

 may expect the water of deep wells to possess a corresponding- 

 rise ; and from such experiments as have been made, there can be 

 little doubt that artesian wells are practicable on a considerable part, 

 at least, of the territory of these formations ; and especially on its 

 eastern portion, at very moderate depths. 



321. The boring of the well at the Penitentiary at Jackson, 

 possesses great interest, not only "for the adjoining country, but for 

 the whole of South Mississipp ; since it will give us definite infor- 

 mation in regard to the general structure of the formations upon 

 which the success of artesian boring will depend. 1 subjoin the 

 record of the strata thus far penetrated in the Jackson well. 



