468 



EErouT — 1891. 



Oxcar Lighthouse. Mean Tidal Effect on Temperature. 



North Carr Light-vessel. Temperature of Water {Monthhj Means). 



Month 



December 



January 



February 



March 



April . 



May . 



June . 



July . 



August 



September 



October 



November 



December 



Januarj' 



February 



Llarch 



The following table shows that when high water occurs at 9 a.m. and 

 low water at 3 p.m. in the warm months, the heating effect of the sun and 

 of the ebb from the Forth makes the water 0°'4 warmer on the surface and 

 0°"3 warmer on the bottom in the afternoon than in the morning. But in 

 the cold months the cold ebb- water from the Forth completely neutralises 

 the feeble heating effect of the sun, and no rise of temperature occurs in 

 the afternoon. On the other hand, when high water occurs in the after- 

 noon in the warm months and low water in the morning, the colder water 



