368 E. W. Hilgard—Oeology of the Delta, etc. 



cone, the glittering of a flowing mudstream was unmistakable 

 Inasmuch as in Morgan's account of his visit the smaller cone 

 IS not mentioned, it is presumable that it has been formed siiuv. 

 by a lateral eruption ; the old cone havino-, perhaps ret. 

 the extreme limit of height to which mudlump force can -: 

 its materials. 



The steep slopes of both the old and new cone are siigg(>- 

 as to the influence of sandiness on that feature, and the expi;::... 

 tjon of the steep inchnation of strata, observed chietlv pi. 

 Southwest Pass. 



It is my impression that another cone exists in the mar.li 

 about two miles south of these. It is almost screened fn a-: 

 view by the reeds, but the telescope shows it to be distin ■' 

 conical. It does not seem to have attracted notic«^ iKrot- ; 



But if mudlump cones are scarce in the marshes, lUc ^ 

 is not true with reference to the salt and gas sprinss, Avhici. , . 

 reported to be quite abundant by the hunters— the oulv n^' 

 whose occupation leads them to "thread the pathless waste" of 

 reedy marsh, otlierwise seldom visited, save by survejing par- 

 ties, and alligators. These springs are found on or around all 

 mudlumps, of whatever age : even on the shoals left behind by 



aismtegrated lumps, where they i 

 altering ]>erceptiblv tlie character 



er in the immediate 

 neighbor h.->o.:l. The Southwest lighthouse was originally built 

 on a mii(llum|) separated from the mainland by a bavou ; this 

 IS now filled up, but salt springs still issue at several points in 

 the marsh near the foot of the tower. It is obvious that the 

 gradual accumulation of deposit is not likely to check lively 

 springs, possessing sufficient head to rise, hydrostatically, above 

 the level of the alluvium ; though in many cases they may lo^c 

 themselves in the sandy strata. 



I have not had an opportunity of ascertaining whether or ' 

 salt springs are known to exist in the marshes near the F^^ 

 and above. I fully expect to find, however, that they do ex 

 though, for obvious reasons, they will become less and : -- 

 abundant as we ascend the river. At New Orleans, as alreaev 

 stated, gas and salt water are reached, and brouodit to the sur- 

 face with considerable vehemence, by bores varvimr from 31 to 

 06 feet ;* and I have no difficulty in believing in'the correct- 

 ness of the impression made upon Col. Sidell, that the fouIv^'■ 

 tions of the New Orleans customhouse were located up-r^ 

 mudlump. t That such obstinate resistance ixs that of the " H 

 of the Passes" to denudation can hardly be attributed to a ::^ 

 of nver deposit, I have already intimated. A large mudkn:, 

 mass has, probably, first caused the deflection. 



[To be continued.] 

 * See above, p. 245. f Lyell's Principles of GeoL, 10th ed., p. 552. 



