410 CARNEGIE INSTITUTION OF WASHINGTON. 



By carrying the theory one short step farther, from the fundamental 

 constants here derived, one may compute approximately the surface 

 current which is produced over the deep parts of the oceans by prevailing 

 winds. One may so secure a valuable quantitative check on the extant 

 theories as to the Gulf Stream, the Japan current, and the Equatorial 

 currents. 



These illustrations suffice to show that the method and constants will 

 be valuable in a variety of engineering and scientific problems. 



After accounting for the wind effects and barometric effects on Lake 

 Erie, while studying the remaining fluctuations that were then unac- 

 counted for, it became evident that the major portions of such short- 

 period fluctuations (periods less than 24 hours) are the well-known 

 seiches. These seiches are free oscillations of the lake surface with a 

 natural period fixed by the dimensions and shape of the lake, persisting 

 for a considerable time, with gradually diminishing amplitude, after 

 a sudden disturbance of the lake surface due to a sudden change of wind 

 or of barometric gradient. 



At Buffalo, during the 22 days of observations which were intensively 

 examined, there was one seiche, on October 27, 1910, with a period of 

 13.1 hours, which had a range of 3 feet during the first oscillation after 

 the initial impulse which produced the seiche. At Cleveland, the same 

 seiche in the first oscillation after the impulse had a range of 1.5 feet. 

 A seiche of this 13.1-hour period is usually in progress at Buffalo and 

 Cleveland. The range of oscillation is, however, usually very much 

 smaller than in the extreme case quoted. 



At Buffalo, the seiche periods of the prevailing seiches were found 

 to be 13.1 and 3.7 hours. 



The 13.1 -hour seiche was identified as being an oscillation of the deep 

 portion of Lake Erie as a whole, lengthwise, from the 10-fathom curve 

 southwest of Buffalo near the east end of the lake to the vicinity of 

 Cedar Point light-house off Sandusky. The portion of the lake ex- 

 tending about 40 miles west from Cedar Point is all rather shallow, 

 less than 7 fathoms deep as a rule, whereas the parts to the eastward 

 concerned primarily in the seiche are nearly all more than 10 fathoms 

 deep. This 13.1-hour seiche prevails also at Cleveland and always 

 differs in phase about 180° between Cleveland and Buffalo. That is, 

 it is high water at Cleveland on this seiche when it is low water at Buf- 

 falo, and vice versa, 



It is very probable that the seiche appearing frequently at Buffalo 

 with a period of 3.7 hours is a free oscillation, lengthwise, of that deep 

 part of Lake Erie which lies between the 10-fathom curve southwest of 

 Buffalo and the constricted part of the lake southwest of the end of 

 Long Point, where the lake-bottom slopes upward, relatively steeply, 

 to the westward from depths of about 20 fathoms to depths of about 

 12 fathoms. This deep portion of the lake which is apparently oscillat- 

 ing as a unit is only about one-quarter of the total length of the lake. 



