CHAP. XXVI.] YELLOW FEVER. 87 



much farther in the interior, and, as he truly remarked, they 

 refute the theory which would refer such accumulations to the 

 Indians, who, it is well known, were accustomed to feed on the 

 Gnatkodon. The distinct stratification seen in some of the 

 heaps of shells and sand at Mobile, also satisfied me that they 

 were thrown up by the action of water. Mr. Hale gave me a 

 map, in which he had laid down the localities of these beds of 

 fossil Gnatliodon, some of which he has traced as far as twenty 

 miles into the interior, the accumulations increasing 1 in thickness 

 in the most elevated and inland situations, and containing 1 there 

 an intermixture of the Neritince with the Cyrena, which last 

 seems only to occur in the recent banks of mud and sand. Mr. 

 Hale observes, &quot; that the inland heaps of shells often rise so far 

 above the level of the highest tides, that it seems difficult to ac 

 count for their position simply by the advance of the delta, and 

 without supposing that there has been a slight upheaval of the 

 land.&quot; 



In the gardens at Mobile there were jonquils arid snowdrops 

 in flower, and, for the first time, we saw that beautiful evergreen, 

 the yellow jessamine (Gehcmium sempervirens), in full bloom, 

 trailed along the wall of Dr. Hamilton s house. Its fragrance 

 is delicious, more like that of our bind- weed than any other scent 

 I could remember. It had not been injured by the late frost, 

 although the thermometer at Mobile had been eight degrees below 

 the freezing point. 



The citizens are beginning to flatter themselves that the yel 

 low fever has worn itself out at Mobile, because the hot season 

 of 1845 was so healthy both here and at New Orleans. Some 

 medical men, indeed, confessed to me, that as the wind blew ibr 

 many weeks from the north, passing over the marshes north of 

 the city during the summer, without giving rise to the usual epi 

 demic, all their former theories as to the origin of the pestilence 

 have been refuted. It may still hold true, that to induce the 

 disease, three causes must concur, namely, heat, a moist ground, 

 and a decaying vegetation ; but it seems clear that all these may 

 be present in their fullest intensity, and yet prove quite innocuous. 

 The dangerous months are July, August, and September, and 



