The age-herald., 1897-09-12
VARYING LAKE LEVELS.
inquiries as to the Causes of the So-CalIed Tidal
 Waves.

From the Cleveland Plain Dealer.
 The peculiar phenomena on the lakes which are popularly, but erroneously, styled tidal waves have attracted att tention and caused speculation among scientists and laymen. The late Col Charles Whittlesey was much interested in the subject and published a mono graph, in which was collected all the information attainable concerning the peculiar oscillations of level observed on Lake Erie, which had no apparent connection with prevailing wind cur rents. A steady wind from one direc- tion piles up'' the water at the lower or upper end of the lake, and materially changes the level for a time, but the. tidal waves" or "seiche," as they are scientifically termed, are of a different character from this piled up" water, and cannot be explained in the same manner. On a still day, when the sur face of the lake is glassy in its tram quility, huge wave suddenly forces it's way up the shore, followed at intervals by one or more of less volume Some times the sudden rise of water is but a few inches; at others, if the reports of excited observers can be trusted, it is as many fee: and runs up the creeks with destructive force. When the tidal waves" have receded the lake is, for while at least as smooth and seemingly. pulseless as before, but it is the gen. eral belief that the oscillations presage a storm.
 At the British Association meeting on Monday MT. F. Napier Denison of the Toronto University read paper on ''The Great Lakes as Sensitive Barometer" in which an attempt was made to ex- plain the causes of these oscillations of lake surface. MT. Denison's observa- tions were taken in the shallower part of Lake Ontario, fronting Toronto, un- der conditions strongly resembling those at the Lake Erie ports where the tidal waves have been most noticed. The records show that the longitudinal and transverse "seiche" movements are very marked preceding and during storms primarily due to differences of atmos- rheric pressure over the extremities of the lake, but greatly augmented, when the gale strikes the water surface. The mean time interval of longitudinal ''seiche' is four hours and forty-nine minutes; the transverse, forty-five min utes. There is a marked agreement be- tween the time intervals of the smaller lake undulations and those found upon the corresponding sensitive biograph traces, both showing predominance of twenty-minute intervals.
 MT. Denison explains the smaller lake undulations as due to atmospheric waves which are seen up along the boun- dary surfaces of different air strata when travelling in opposite directions. The action of these atmospheric waves upon the surface of the water tends to form minute undulations, which increase in amplitude as they move into bays, where the water becomes shallower, until finally they assume the propor- tions as recorded upon the instrument.
 It was found that marked rapid and large undulations often occur during the autumn and winter months upon both instruments, when the barometer Is ac- tually rising and fine weather prevails over all the surrounding territory. The explanation is that at such times an area of low pressure, a. cyclone, is situated over the south or southwestern states. which usually moves over or near to
 
 corded atmospheric waves are due to the lower, denser air of the anti-cyclone moving toward the southwestern cy- clone, along whose upper boundary sur face huge waves, extending to the earth, are set up by the rapidly opposing upper poleward current. The mean velocity of this upper current in summer is sixty miles per hour, and in winter 110 miles per hour. On the other hand, during the approach of an anti-cyclone, at tended by fine weather and westerly winds, these lake undulations become extremely small because the lower air moves in approximately the same direc- tion as the upper poleward current. In illustration of the direct action of these air waves upon the surface of the lake MT. Denison notes that on March last during the passage of several successive huge atmospheric pillows" the water rose SIS inches in ten minutes, then fell 101s inches in fifteen minutes, followed by the phenomenal rise of 111s inches in fifteen minutes.
 The information obtained from fisher- ermen on Lakes Ontario, Erie, and Hu- ron shows that a twenty-minute inter- val has been frequently observed be- tween the two or more so-called tidal waves" that follow each other.
  Dress I .ininoc at New Vorl-