108 EXCAVATION FOR GAS-WORKS. [CHAP. XXVIH 



Mint at New Orleans, estimates the height of some of these shell 

 banks north of the lake, at twenty feet above its level ; yet h$ 

 thinks they may have been washed up by the waves during 

 storms. I suspect, however, that some change in the relative 

 level of land and sea has taken place since their accumulation. 

 Dr. M Cormac informed jne that he had observed heaps of these 

 same shells recently cast up along the margin of the bay called 

 the Sabine Lake, where the waters of the delta are brackish. 



Returning to the bayou, we passed a splendid grove of live 

 oaks on the Mctairie ridge, supposed by some to be an old bank 

 of the Mississippi. These bayous, which traverse the delta and 

 alluvial plain of the Mississippi in every direction, are some of 

 them ancient arms of the great river, and others parts of its main 

 channel which have been deserted. They are at a lower level 

 than the present bed of the river, and convey the surface-waters 

 to the sea from that part of the land which the Mississippi is 

 incapable of draining. The bayous are sometimes stagnant, and 

 sometimes they flow in one direction when they convey the sur 

 plus waters of the Mississippi to the swamps, and in an opposite 

 direction at seasons when they drain the swarnps. 



When we reached the canal which connects Lake Pontchar- 

 train with New Orleans, we found its surface enlivened with the 

 sails of vessels laden with merchandize. On the stern of one of 

 these I read, in large letters, a favorite name here &quot; The Dem 

 ocrat.&quot; Many features of the country reminded me of Holland. 

 About a mile from the city we passed a building where there is 

 steam machinery for pumping up water and draining the low 

 lands. 



It is not easy for a geologist who wishes to study the modern 

 deposits in the delta, to find any natural sections. I was there 

 fore glad to learn that, in digging the foundations of the gas-works, 

 an excavation had been made more than fifteen feet deep, and 

 therefore considerably below the level of the Gulf, for the land at 

 New Orleans is elevated only nine feet above the sea. The con 

 tractors had first hired Irishmen, with spades, to dig this pit ; 

 but finding that they had to cut through buried timber, instead 

 of soil, they were compelled to engage, instead, 150 well-prac- 



