GEOLOGICAL AND MINERALOGICAL NOTES. 73 



peat beds and the compared soundings in the harbors 

 clearly indicate this. 



During the past summer, Lieutenant Ripley, U. S. N., 

 and a corps of assistants, have been surveying Salem har- 

 bor in connection with the work of the U. S. Hydrographie 

 Survey. Lieut. Ripley has authorized nie to say that 

 the results of his work show a greater depth of water over 

 all the ledges in the harbor than was recorded by Dr. 

 Bowditch in 1804-5, and that the seaward slope in the 

 outer harbor has apparently deepened from one to one 

 and one-half fathoms since that time. This corroboration 

 of my observations is especially gratifying for the reason 

 that I had no knowledge of the work of the survey until 

 these results were obtained. 



From the aeeepted rate of subsidence, — two feet for 

 each Century, — and as indicated by my observations here, 

 it is fair to assume that the peat beds stood in their nor- 

 mal position and that the trees, whose remains we find to- 

 day beneath the ocean, were flourishing in their füll 

 growth from one thousand to twelve hundred years ago. 



ESSEX INST. BULLETIN, VOL. XXVI 10 



