258 RESULTS OF COMPARATIVE OBSERVATIONS : SWITZERLAND. 



The facts shown in the preceding table, when reduced to graphic rep- 

 resentation, appear as follows : 



Mean temporatnre of the trees above or below the mean temperatiu-e of the air. 



In these results we observe a greater regularity and less differences 

 in the beech than in either of the coniferous species, apparently due to 

 differences in their conductors of heat, rather than an external cause. It 

 does not appear but that the exposures were alike and that the external 

 conditions were essentially the same. 



