134 SHELL EOAD 8 [CHAP. XXVIII. 



March 5. 1846. From New Orleans I made a 

 short excursion with Dr. Carpenter and Dr. M Cor- 

 mac to Lake Pontchartrain, six miles to the north 

 ward. We went first along the &quot; shell road &quot; by the 

 Bayou St. John s, and then returned by the canal. 

 The shell road, so called from the materials used in 

 its construction, namely, the valves of the Gnaihodon 

 cuneatus, before mentioned, is of a dazzling white 

 colour, and in the bright sunshine formed a strong 

 contrast with the vegetation of the adjoining swamps. 

 Yet the verdure of the tall cypresses is somewhat 

 dimmed by the sombre colour of the grey Spanish 

 moss hanging everywhere from its boughs like dra 

 pery. The rich clusters of scarlet and purplish fruit 

 of the red maple (Acer Drummondii) were very con 

 spicuous, and the willows have just unfolded their 

 apple-green leaves. The swamp palmetto ( Chamce- 

 rops adansonia) raises its fan-shaped leaves, ten feet 

 high, although without any main trunk, like the sea- 

 island palmetto before described. Several of them 

 are surmounted by spikes bearing seeds. Among 

 the spring flowers we gathered violets ( Viola cucul- 

 lata\ the elegant Houstonia serpyllifolia., which we 

 had first seen at Claiborne, and a white bramble 

 (Rubus trivialis), the odour of which resembles that 

 of our primrose. The common white clover, also, 

 is most abundant here, as on the banks of the Mis 

 sissippi, below New Orleans ; yet it is not a native of 

 Louisiana, and some botanists doubt whether any 

 of the European species now growing wild in this 

 State are indigenous. 



Lake Pontchartrain is about fifteen feet below 



