344 Tattle — Changes in Elevation of Land and Sea. 



As the effect of the atmospheric pressure and winds on the 

 sea level at any place is the integral of their effects taken over 

 a wide area, while these observations are taken at only one 

 point, a close correspondence is not to be expected, particu- 

 larly where the locality is at the junction of continental and 

 ocean areas, as in this case. 



It has been recently found from the yearly averages of atmos- 

 pheric pressure at many widely separated places, that abnor- 

 mal variations of atmospheric pressure occur of considerable 

 duration, which are apparently caused by the surging to and 

 fro of the atmosphere. They affect a very considerable area 

 and have a tendency to recur in periods of about three and 

 eight years, corresponding closely with periodic variations of 

 solar energy received by the earth. 



The examination of long series of tidal observations in places 

 scattered over the world discloses very similar periodicities, 

 which are doubtless due in the main to the surging of the baro- 

 metric pressure before alluded to, and the consequent change 

 in the atmospheric circulation. 



Tidal observations from Maine to Florida disclose a striking 

 similarity among the changes in half tide level at all localities 

 on the Atlantic Coast, and the same phenomena have been 

 observed on the shores of the Baltic Sea. It appears quite cer- 

 tain that these fluctuations of yearly half tide level, nearly 

 alike in direction and amount, are due mainly to changes in 

 the m£an annual barometric pressure, and the accompanying 

 changes in w T ind velocities. These periodic fluctuations, never 

 more than a few years in duration and very much alike in 

 extent and direction at all the points embraced in a large 

 area, evidently are changes due entirely to the sea, and can 

 in no way be considered as showing a change in the absolute 

 elevation of the land. 



On the other hand, there are no changes in the meterological 

 phenomena wdiich will account for a continuous increase of 

 half tide level for a series of years, such as have been observed 

 at New York from 1875 to 1902, at Boston for the same period, 

 and at Penobscot Bay from 1870 to 1885. Neither will such 

 changes account for the continuous depression of sea level 

 shown by the series of observations at Stockholm, Sweden, 

 commencing in 1774, and verified by numerous observations 

 along the Swedish coast of the Baltic Sea, where it has been 

 found that the land has risen nearly two feet relatively to the sea, 

 while equally reliable observations on the German coast of the 

 Baltic Sea, dating from 1811, show no appreciable change in 

 level. 



No long period or continuous variations of atmospheric pres- 

 sure, winds, temperature, ocean currents, etc., appear to exist to 



