378 



NOTES ON GEOLOGICAL KESULTS. 



Point and La Moje Point. As far as my own observations 

 go the layers found at St. Martin's Point are much the 

 best example of this formation. Here we have practically 

 four bands of varying depth of from 3 or 4 inches to 12 to 16 

 inches. 



These concretions are hard and not capable of being 

 broken by hand, but with the hammer they break easily with 

 a friable fracture, showing granular surfaces. In the fractures 

 are found minute pieces of shell, frequently with a cast of the 

 shell originally enclosed but now dissolved. There are also 

 found whole shells (to be described later), but, with one 

 exception, these shells have not been found in the clay deposit. 



The concretions are covered and interlayered by clay 

 in which there is comparatively little sand. The clay itself 

 is layered, hence is of fluviatile origin. 



The mode of origin of the concretions appears to be 

 as follows : A mild period, as regards climate, enabled the 

 shell life to exist, but probably hot summers and cold winters 

 followed each other with greater extremes of temperature 

 than at present. This would cause the washing down of clay, 

 shells and vegetable matter, and would also account for the 

 stratification noticed in this deposit.* 



Assuming that the shells were equally divided among the 

 clay of the deposit, but now are found in the concretions 

 only, we may take it that the shells themselves have caused 

 the concretions. 



The solution of the carbonate and phosphate of lime has 

 formed the clay into an indurated cement, the concretion being, 

 in fact, a natural concrete. The water thus charged with 

 lime penetrated a few inches only and then its lime formed 

 the first layer of concrete. This being impervious arrested 

 the action, as far as the underlying clay is concerned, but the 

 band would naturally thicken above until all the shells in the 

 immediate super-imposed clay w 7 ere dissolved. 



The layers being four in number, and at distances varying 

 from 1 to 2 feet, show that the processes of deposition and 

 solution were arrested and resumed at least four times. Of 

 course these bands, being on the eroded edge of the cliff', 

 are only slight remnants of much larger deposits and their 

 horizontal position points to a past flat area extending over the 

 present sea at an elevation of nearly 50 feet. 



At Divette and Fermain I cannot trace the bands, but find 

 that the clay in which they were has slipped and the con- 



*The stratification is not visible everywhere, but is well seen at Divette, St. 

 Martin's Point and Fermain. 



