As another example of the disturbance of water at the time of a great earthquake in districts where the earthquake was not felt, may be mentioned the swelling of the waters of the Marañon, in 1746, on the night when Callao was overwhelmed. Sudden variations in the level of the water have been many times observed in the North American lakes. The changes in level which sometimes take place in the Genfer and Boden lakes are supposed to have some relation to the condition of the atmosphere. A rising and falling of especial note took place on April 18, 1855. In Switzerland these sudden changes are known as ‘seiches’ or ‘rhussen.’ From the observations and calculations of Prof. Forel it would seem that the period of the ‘seiches’ depends upon the dimensions of the lakes; the calculated periods dependent on the depths of the lakes being approximately equal to the observed periods.[150] W. T. Bingham, writing on the volcanoes of the Hawaiian Islands, remarks that it is not unusual for the sea to be agitated by great and unusual tides, and that such sea waves have not been attended with volcanic eruptions or seismic disturbances. Thus in May 1819 the tide rose and fell thirteen times. On November 7, 1837, there was an ebb and flow of eight feet every twenty-eight minutes. Again, on May 17, 1841, like phenomena, unaccompanied by any other unusual occurrences, were recorded.[151] Phenomena which may possibly hold a relationship to earth pulsations are the periodical swellings of the ocean on the coast of Peru. Dr. C. F. Winslow, who made a long period observation upon the coast of Peru, found ‘the highest tides to prevail at Callao and Paita in December and January,’ and ‘also a series of enormous waves or sea-swells to be thrown from time to time upon the coast, varying from twenty-four to twenty-seven hours in continuance, accompanied by unusual height of the tide during the same period.’ During June and July the ocean was unusually tranquil. These phenomena do not appear to be connected with great atmospheric storms, nor do they hold any relation to the prevailing wind. They increase with and accompany the swelling of the tides, and occur generally, but not always, about full moon. Sometimes they break suddenly upon the coast. ‘_They are annual and constant in their periodicity._’ The periodical swellings are most noticeable between Tumbez 3° S.L. and the Chincha Islands 14° S.L. These oceanic phenomena synchronise with the periodic intensity of earthquake phenomena in that part of the globe, and these with tidal movements.[152]