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u'O receives as compared with the other; to the iuflu- 



L of prevailing winds according to the station, position 



L'X[iosiire; or to locid or general magnetic influences — 



oal as peculiar to small areas, or general as pertaining to 



i'ger or extensive regions. An accumulation of data 



iT»'g,"ht show a marked and constant character in the relation 



;;imeters to such factors of the environment; and also 



iked character in the diameters of one region, as a 



0. when compared with another region, where modi- 



)r different chmatic conditions exist. 

 1 i a comparati vely arid region, with a high mean tem- 

 ture and infrequent rainfall and a dry atmosphere, we 



suppose that the southerly half of a tree, following the 

 V of its circumference /row east by loay of south to west, 



t, through excess of light and heat, suffer from dessi- 

 iiig influences, and make a less growth than the nortli- 

 \ half, following the curve of the trunk /rom ea^^ byway 

 / )i'fh to 'rest, as the northerly half would have the ad- 

 itage, if advantage it be, in such a climate, of less light 

 1 iieat and more" shade; while in a region less arid wath 

 iiuch lower mean temperature, etc., the greater propor- 

 n of light and heat which the southerly half receives, 

 uld give that side of the tree an advantage over the 

 rtherly half. 



As to the effect of prevailing winds in differentiating the 

 nneter, we may suppose that the side of a tree most 

 })Osed might be affected, and the growth on the wind- 

 rd side much modified or repressed; while the leeward 

 sheltered side, being protected, would exhibit a greater 

 imeter or semi-diameter, measuring from the true center 

 tlie tree, i. e., from its initial ring. 

 In the " big tree" measured by Professor AVhitney, the 

 itherly half of the diameter shows the excess, indicating 

 It heat and light were specially advantageous; but here 

 Itude comes in as a factor, as the height of the Calaveras 



