50 Conservation Department 



sions, bad weather interrupted the work at Dunkirk or Port Dover 

 or both, and the interval between the first and last stations was 

 correspondingly lengthened. The lake is so large, however, and its 

 diurnal changes, even under the influence of a brisk wind are so 

 small that mean temperatures can be discussed and contour lines 

 of distribution draw^n as safely as though it had been possible to 

 occupy all of the stations within the same twenty-four hours. 



Cruise 1 began on July 24 and continued, with interruptions 

 due to bad weather, until July 31. The distribution of surface 

 temperature was in accordance with Fig. 4. There was a pro- 

 nounced piling up of warm water along the American shore and 

 into the pocket at the Buffalo end of the lake. The Dunkirk region 

 was warmest with water slightly above 23° while all the Long 

 Point bay region was covered by water below 21°. 



When station 14 was occupied the relatively feeble penetration of 

 vernal warming was evident and the first evidence of a thermocline 

 observed. There was a drop of 10° in the ten meters between the 

 10 m. and 20 m. levels and at the bottom in 36 m. water of 4.7° was 

 encountered. 



A stop of 18 hours was made at the next station, 15, the ''deep 

 hole". Here the temperature Avas taken every 5 m. down to the 

 30 m. level and then every 10 m. to the bottom in 60 m. True 

 winter water of just above 4° was found in the bottom 10 m. and 

 a marked discontinuity layer occurs between 25 and 35 meters. 

 The finding of the 4.7° water at station 14 was now explained and 

 a glance at Fig. 5 shows a rather widespread distribution of water 

 below 5°. Rather surprising was the fact that this cold water 

 seemed to be running up hill a little, for 4.7° occurs at a level 

 10 m. higher at station 14 than at station 15. But this inclination 

 of the water layers occurs in a manner truly remarkable on the 

 northern side of the "deep hole" where at station 17 where water 

 fractionally above 5° is found at 15 m. although six miles away at 

 station 15 it is 40 m. below the surface. 



The most remarkable discovery at station 17 was the existence 

 of a thermocline in which a change of 7.8'° takes place in a vertical 

 distance of only one meter — between 14 m. and 15 m. Such a 

 condition has never been found before in a large and exposed body 

 of water so far as I can find out; and in order to make certain 

 of this phenomenon the readings were repeated three times with 

 different thermometers. The region is one of strong currents and 

 wave action. This cold water which climbs uphill against the 

 force of gravity extended a certain distance ''around tlie corner" 

 into Long Point bay. But to tlie westward of the neighborhood of 

 liluff ])ar there was citliei- no further intrusion or tlu^ sun's rays 

 had penetrated tli(» sliaHows sufficiently to make tlie water virtu- 

 ally uniform from toj) to bottom, there being a differential of only 

 0.&° at the station 18 and of 1.8° at stntioii D. 



It may be considered that the to)) 10 meters of the lake were 

 now pretty thoroughly mixed, the mean surface temperature being 

 21.8° and the mean for 10 m. being 20.!)°. l)Ut this mixing did not 



