L. C. JOHNSON — THE NITA CREVASSE. 23 



gathered in the folds of the mantle and between it and the shell, the bars or reefs 

 throughout the region were within a month actually silted over and buried, some of 

 them several inches deep, in the fresh material from the crevasse. From May 24 to 

 May 30 railway parties working in the vicinit}' of Gulfport, who were in the habit of 

 seining for fish in the sound, found the firm, sandy beach bottom, the delight of 

 bathers, covered by a brown yellowish ooze ; and instead of red-fish, pompano, sheeps- 

 head and Spanish mackerel they caught only catfish and buffalo — inhabitants of 

 muddy inland lakes — with a few scattering mullets. 



Tracing the waters back to their source, their work may be better understood. 



At the break the immediate action was destructive. Except where there was little 

 or no current there was no deposition of sediment, although in the wake of stranded 

 houses and other obstructions elongated banks or ridges of sand and mud were formed, 

 and these included many fragments of the wrecked houses and mills. In one case 

 many iron implements were found embedded in the sand and silt with leaves, sticks 

 and other debris. A part of this silty sediment, but with less and less of sand, was 

 deposited eastward along the bayous and timbered bottoms between the crevasse and 

 Lake Maurepas. On the large flat prairie or pine meadow towards Ponchatoula, the 

 water, deep as it was, left no sand, but only a fine, impalpable, yellowish or bluish- 

 brown clay, such as constitutes the basis of the pine meadows from Ponchatoula to 

 Escatawpa river. 



The bed of the sound itself does not seem to have been aftected during recent years 

 by the various inundations and the constant contributions from the rivers — that is, 

 there is no proof of filling up ; there seems to be the same stiff blue clay, overlain by 

 ocean sand, that was first reported ; the same average depth ; the same shelving bot- 

 tom, sloping gulfward about 3 feet to the mile for the 12 to 15 miles of its width. 

 Yet the filling-up goes on. The river contributes its clay, to be covered by the tides 

 with sand, regularly, slowly, from year to year; but at an equal pace with this goes 

 on a subsidence, slowly, steadily ; and for no recent historical period can we exactly 

 measure the rate. We can observe that the oldest shell heaps of the aborigines were 

 of Gnathodon shells, with some fresh water and land moUusks ; we can see that the 

 bases of the shell heaps have sunk below tides now and probably 10 to 15 feet below 

 the shore elevation of the beginning; we can cut into these and find some of them 10 

 to 20 feet deep, and observe that, above the brackish water Gnathodon remains, later 

 occupants of the camps have piled 8, 10 and 12 feet of oysters and conchs, proving 

 that latterly the salt tides have reached farther up the rivers and bayous than when 

 the settlements were first located and the inhabitants lived mainly upon the fresh and 

 brackish water mollusca; but as to the time in years, there is wanting a common 

 standard of measurement. The time was so considerable that the fresh-water shells 

 are mostly crumbled to powder; the Gnathodon shells are much decayed, and only 

 the more enduring shells of Ostrea remain as sound as ever. So sound and abundant 

 are these that, without much apparent diminution, the shell heaps have furnished 

 material for streets and roads and quicklime for the cities and settlements of the coast 

 from the first occupation of this region until recent transportation facilities rendered 

 northern lime cheaper than the older wood-burnt supplies. Similar evidence of sub- 

 sidence, even to a greater degree, on Mobile bay was thought worthy of notice by 

 Professor Tuomey.* Such facts are not uncommon in other parts of the world, but 

 the subject is only incidentally of interest in connection with the matter in hand and 

 need not be pursued further. 



*2nd. Bien. Rep. Geol. Survey of Ala., 1855 (1858), p. 148. 



