332 On the Secondary and Tertiary Formations. 



Art. VIII. — Ohservations on the Secondary and Tertiary Forma- 

 tions of the southern Atlantic States ; by James T. Hodge, 

 Member of the Association of American Geologists.* With an 

 Appendix, by T. A. Conrad. 



Messrs. Editors, — Having spent a few months of the last 

 year in making a tour on horseback through parts of the south- 

 ern Atlantic states, I have put some of my observations into the 

 present form, and if you deem them worthy of a place in the 

 American Journal of Science, they are at your service. My 

 object was to obtain from my own notice a general idea of a 

 large portion of our country not familiarly known, but so rapidly 

 did I pass through it, that my notes are crude and imperfect. 

 From the investigations of Mr. Conrad, to whose instructions I 

 am much indebted, the accompanying lists of fossil shells, which 

 I there collected, were made out, and a few new species are 

 now added to our catalogue of the tertiary fossils. 



Until I arrived in the southern part of Virginia I was unable 

 to see much of the " marl beds" of the tertiary, owing to the 

 snow and ice that covered the ground. I found, however, that 

 the marl extended all along the eastern section of the state, and 

 that it was extensively used as a manure by the planters. On the 

 Rappahannock, seven miles below Fredericksburg, the bed is at 

 least ten feet thick, and so conveniently exposed that vessels might 

 come alongside and load with it, if it were important enough to 

 transport. It here abounds in shells, and also contains teeth of 

 sharks, and fossil bones. Nearly all belong to extinct species, 

 and the genera besides are those most common to the lower 

 tertiary. The fertilizing properties of the marl appear to depend 

 almost entirely upon the carbonate of lime afforded by the slow and 

 long continued decomposition of the shells ; it contains more or 

 less of the green sand, but in too small proportion to add much 

 to its richness ; and the quartzose sand and mica that constitute 

 the remainder of it can be of little service. The effect of this 

 marl upon the cotton and clover is superior to that of any other 

 manure, but then it is put on at the rate of 700 bushels to the 



" The substance of this paper was communicated to the meeting of the Associ- 

 ation of American Geologists, as referred to in the report of their proceedings, 

 published in the last. 'Ho.— Eds. 



