626 



MR E. M. WEDDERBTJRN ON THE TEMPERATURE SEICHE. 

































Moritzfelde, 12th August 1910. 











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10-00 



7-5 



12-00 



7-6 



14-30 



11-5 



16-00 



7-7 



18-11 



7-5 



21-35 



7-3 



24-05 



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20 



























14-56 



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20 



19 

 18 

 17 

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2-08 

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7 : 8 



8 : 3 



4-09 



8-0 



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8 : 2 



8 23 



8-37 

 8 31 

 8-47 



8-0 



8-8 



9-2 



10 2 



10-05 

 10-15 

 10-10 

 10-26 



8-4 



9 



11-1 



15-1 



12-05 



12 -10 



12-35 



7-6 



7 ; 7 

 16-4 



14-42 

 14-37 

 14-34 

 14-51 



8-6 

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16-05 

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18-16 

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18-28 



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15 



14 

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2-33 



2 21 

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2-45 



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4-05 

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 4 39 



10 

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 15 



16-5 



6-12 

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 6-23 

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11-5 

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 16-8 

 16 8 



8-56 

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16 6 



17 



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12-25 

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18-33 

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12-2 

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21-55 

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6 33 



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9-08 



17-2 



10-42 



17 3 



12-39 



17-4 







16-26 



17-5 







22-35 



17-6 



24-40 



17 7 







If the observations at midday and 2 p.m. (14 h.) are referred to, it will be seen that 

 the temperature changes are very erratic, and that at the same time the discontinuity 

 in temperature is very sharp. At midday a difference of 9 *3° C. between 14 and 

 15 metres of depth is recorded, and though it is probable that this is exaggerated by 

 convection currents and the fact that the observations were not made simultaneously, 

 even at 1 6 h. (4 p.m.), when the observations indicate a steadier state of affairs, there is a 

 difference of 7 "8° C. in one metre, and at midnight one of 6*4° C. Other examples of 

 sharp temperature discontinuities are a difference of 67° 0. in one metre on 26th, on 

 27th July of 6 *4°, at midnight on 12th August of 6*4°, at 4 a.m. on 13th August of 

 57°, and at 6 p.m. on 13th August of 7S C C. 



§ 15. It was noted in Loch Ness that the discontinuity was sharper at the lee than 

 at the windward end of the lake. This was also the case in the Madiisee, and is well 

 illustrated by fig. 3. The heavy continuous line in this diagram shows the maximum 

 fall in temperature through one metre at Moritzfelde — taking means of the maxima from 

 each day's observations. The broken line shows the same thing for Werben. When 

 these curves are compared with the wind directions previously given, the relation between 

 Avind directions and the sharpness of the discontinuity is at once apparent. It is also 

 seen that the stronger the wind the sharper becomes the discontinuity. The explana- 

 tion of this last phenomenon is that a strong wind mixes up rapidly the surface layers 

 which in calm weather get heated up by conduction, solar radiation, etc. This is 

 illustrated by fig. 2, for it is seen that the strong winds blowing on 12th August 

 bad the effect of making all the isotherms from 10" to 17° bunch together; that is, the 



