114 The National Geographic Magazine 



TIMBERLINE 



IN the last number of the National 

 Geographic Magazine* the dis- 

 tinguished geologist and physiographer, 

 Prof. I. C. Russell, discusses the sub- 

 ject of timberline, and suggests the use 

 of the term in at least three different 

 senses. It is seldom that I find myself 

 called upon to differ from this eminent 



*Nat. Geog. Mag., vol. xiv, no. 2, pp. 80-81, 

 February, 1903. 



authority, but in the present instance 

 I feel it my duty to file a protest. 



The term ' ' timberline ' ' has come to 

 have a perfectly definite and well-under- 

 stood meaning, accepted by naturalists 

 the world over. It is the upper or boreal 

 limit of tree growth as determined by tem- 

 perature. To use the term in other senses, 

 as for upper limits of tree growth not 

 dependent on temperature, for lower 

 or austral limits of tree growth on moun- 

 tains or other slopes, for the line where 



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Chart Showing Annual Precipitation at Salt Lake City and Water Level of 



Great Salt Lake 



EXPLANATORY NOTES. 



The upper line indicates the precipitation and the lower one the lake level. 



Broken lines indicate periods of no authentic observations, or that the data have been 

 approximated. 



This chart was prepared by Mr L. H. Murdoch to illustrate his article on " Why Salt Lake 

 has Fallen," in the last number of this Magazine. 



