256 PROCEEDINGS OF THE ACADEMY OF [1884. 



borhood of the latter town, and is characterized b3' the numerous 

 particles of green sand contained in it. The thickness could not, 

 however, be accurately determined, running as it does, indistinctly 

 into the overlying gravels. West of the railroad, the deposit 

 thins out entirely, and does not again appear. Along the ravine 

 made by Scott's Run the red sand has been found Ijing upon the 

 shell marl, running to the south into a black decomposed green 

 sand. Notwithstanding the deposit of red sand, which outcrops 

 along the south shore of the canal, the shell marl is dug by several 

 parties on a strip along the same side, and for this reason, I have 

 extended the southern limit of the lower marl belt slightly to the 

 south of the southern shore of the canal. 



Considering the foregoing facts, the writer with some trouble 

 that cannot well be removed, has referred the reddish yellow sand 

 stratum to the red sand of Prof. Cook. This red sand occupies 

 a narrow strip along the south side of the canal, to the east of 

 the railroad, and runs to the south beneath the overlying stratum 

 of decomposed marl, by which nearly the whole area of the bed 

 as previously marked out, is covered. From this we see that the 

 true red sand, which is so extensively developed in New Jersey 

 has a less thickness in Delaware, but is replaced by the indurated 

 marl, which in New Jersey is found more thickly exposed, but 

 occupying the same stratigraphical position above the red sand. 



Indurated Oreen Sand. — This marl attracts from the observer 

 more attention than any other, coming to the surface as it does 

 in numerous localities, and having been extensively worked for 

 its pre-eminent qualities as a fertilizer. 



Already in a state of partial decomposition, the decay rapidly 

 progresses by the removal of the potash, and the oxidation of the 

 ferous salt of iron, or its direct solution by carbonated water. 

 Generall}^ speaking, the marl in the bed is of a black, loamy 

 nature which, when dry, assumes a brownish or grayish tinge. It 

 is made of a variable quantity of green sand, with a large pro- 

 portion of siliceous sand. In some places the marl is found to 

 contain a large amount of argillaceous matter, while again it is 

 extremely clean and dry. It differs entirely from the lower marl, 

 by containing no carbonate of lime in the pulverent state ; but 

 in certain places the deposit abounds in shells, which renders it 

 comparable with the shell marl of the former formation. 



Examined with a glass, the grains of indurated marl prove of 



