170 THE AMERICAN MONTHLY [June, 



brown deposit, I consider that I have reached the ancient 

 deposit laid down in open water. Here I examine for 

 diatoms, as from this point to the bottom wliere gravel 

 or hardpan is found the deposit should contain more or 

 less diatoms ; near the bottom the stratum should be 

 quite rich. 



In many swamps this stratum will be found to aver- 

 age about two feet in thickness, in others the strata may 

 alternate to a considerable depth; in those connected 

 in a series at different levels through which a stream 

 flows or did flow in ancient times the deposit may be 

 of great thickness. I have known it to exceed seventy 

 feet. These thick deposits are not necessarily any more 

 ancient than others of moderate depth, the differing 

 surroundings and circumstances being sufficient to ac- 

 count for them. 



The boring apparatus described is intended for use 

 only in soft deposits of no unusual depth, it brings up a 

 large amount of material and will work under water, 

 but for hard or dry deposits its use would be impracti- 

 cable ; dry deposits are best reached by simply digging. 



For the marine deposits of the salt marshes a cylinder 

 two inches in diameter would probably be best. On the 

 Connecticut shore some of the larger ^estuaries were 

 filled first with a deposit of fine clay of glacial origin, 

 which seldom contains any organic material. In the 

 Quinnipiac marshes this clay has been bored to a depth 

 of over fifty feet without penetrating through it. The ma- 

 rine deposit overlaying this clay is only six or eight feet 

 thick, but some parts are very rich in diatoms. Ancient 

 marine deposits similar to those of j)arts of New Jersey, 

 Md., Va., and California cannot be expected to be found 

 north of the limit of glacial flow ; all such deposits were 

 thoroughly ground up and carried away during the ice 

 period ; but the time since then has been sufficiently 

 long to produce an abundance of fresh water deposits, 



