IN THE NORTH AMERICAN LAKES. 23 



vain and thunder-storms arc produced in this way. A brr(>zc from the water press- 

 ing against the side of an abrupt liighUmd chain fnupicntly causes its summits to 

 be enveloped in fogs and clouds of condensed moisture. Fogs excite electrical 

 action like clouds, though with less intensity. Winds and unequally heated bodies 

 of air may produce the same effect, causing rapid undulations in the atmospliere, 

 and these may be transmitted to the water beneath. 



Without offering this as a satisfactory explanation, 1 jjresent it for consideration. 

 To discuss the question rationally, we need observations upon the electrical state 

 of the atmosphere during a period of oscillations.' 



Upon Huctuations caused by winds it will not be necessary to enlarge, as they 

 are produced by a visible cause, and little is left for speculation. The mecluini(-al 

 power of winds, heaping up water on a lea and depressing it on a windward shore, 

 is generally known. On the North American Lakes the registers show that it is 

 a force worthy of attention where the construction of harbors and piers is con- 

 cerned. In such cases there must be added to the general stage of water something 

 for the temporary rise due to storms. 



Certain winds cause at the same place a greater rise than others. At each port 

 the amount of this kind of fluctuation is shown by the daily registers for each 

 direction of the wind. I select some instances from the tables in my possession, 

 choosing from among those on Lake Erie only such as were registered three times 

 a day, and on Lake Ontario once a day. 



Those at Cleveland are from Colonel Stockton's observations; those at Buffalo 

 from Mr. Lathrop's; and at Oswego they are taken from those of Messrs. Hatch 

 and Malcolm. 



[' The simplest hypothesis for the explanation of these phenomena is, that they are prodnccfl I)y the 

 pnssa-re of thunder-storms, and perhaps, in some eases, of water-spouts, across distant parts of the 

 Lake'' It is well established, by observations at this Institution, that rapid oscillations of the barometer 

 are produced during the passage of a thunder-storm across the meridian of this city. The mercury sud- 

 denly descends, then rises a little, and again falls, and after this regains its former level as the storm 

 passes oir to the east. A thunder-storm, therefore, crossing the lake at a distance, would transnnt to 

 the place of observation undulations from every point of its path, and these, arriving in success.o.., 

 would produce effects similar to those described. This hypothesis can be tested by the observations which 

 are now about to he established along the lake.-SEC. Smithsonian Instituti n.] 



