70 



FOREST INFLUENCES. 



the coustautly cooling mean temperature. These features may be in 

 part due to tlie soil. Otherwise the diagram resembles the correspond- 

 ing one of the preceding section. Fig. 41 gives the two forest tem- 



Pio. 40.— Fure.st temperature, dittereneus at Erineuouville, iiudir iiines. Soil: coarse, bare saiid. 



perature diagrams above trees from M. Fautrat's observations. The 

 line for mean temperature is omitted because of the narrowness of the 

 space. It would, in each case, hug the zero line. It is interesting to 



EVERGREEN TREES. 



MINIMA. 



.MEAN. 



MAXIMA. 



Fig. 41.— Forest temperature, ditiereiices above trees — from Fautrat's observations. 



note how the temperature diagram, iu Fig. 41, has here contracted. 

 That for everg.een trees, with the instruments close to thetoj>s, is very 

 narrow, while that fo^ deciduous trees, instrument about 20 feet above 



. EVERGREEN TREES.. 



AVERAGE OF BOTH. DECIDUOUS TREES. 



Fit). 42. — Vertical f iiiiperatiire •gradients finm (ibscrvations above trees. 



the tops, has contracted so as to vanish at times. It is evident that if 

 the instruments had been put a few feet higher up it would have en- 

 tirely disappeared. Fig. 4"J represents the vertical gradients from M. 



