Pooi-E — On the Convection of Heat in Vertical Water Columns. 271 



evidence of a maximum at about 17° C. followed by a fail for higher 

 temperatures. With double columns the results were much more consistent, 

 the heat flow for a given gradient iDcing approximately proportional to the 

 excess of the mean temperature above 4° C. 



We should expect, at fii'st sight, that the flow of heat should increase 

 with the temperature at about this rate, owing to the increase in the coefficient 

 of expansion and the decrease in the viscosity. The contrary results obtained 

 with the single column are probably to be ascribed to the increased mixing 

 of the ascending and descending currents with rise of temperature. In the 

 ease of the double tube this mixing cannot occur. 



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-/ 



Fig. 2. 



Results. 



The results for single columns are plotted in fig. 2, and those for double 

 columns in fig. 3, the lengths and diameters being shown on the figures. Since 

 it was desired to estimate the probable magnitude of the effect of convection 



