184 Proceedings of Royal Society of Edinburgh. [sess. 
solar radiation penetrates in the waters of the Mediterranean 
does not exceed 20 metres, and the accumulation of heat within 
this layer during the sunshine of a September day may be 
estimated at 450 calories per square centimetre of surface, or 
about two- thirds of the available radiant energy incident on the 
surface. 
These, broadly speaking, are the conclusions to which a study of 
the Pola observations seems to lead. But it is obvious that a 
much more valuable set of data would he obtained by the use of 
several platinum thermometers permanently fixed in mid-ocean at 
convenient depths, and read at fairly frequent intervals through- 
out the day and night, under different atmospheric conditions as 
regards cloudiness and wind. 
(. Issued separately April 4 , 1904 .) 
