INTRODUCTORY EXPLANATIONS. 21 



or comparative frequency within those areas, is in itself any 

 " knowledge of causes and their effects, and of the laws of 

 nature." Information on those points is to be acquired and 

 arranged, no doubt; and yet something more than that kind 

 of infonnation has stiU to be acquired, before we can as- 

 siune to be philosopical observ^ers of nature, — investigators 

 of causes ^and effects, and of natural laws. It is in the 

 digestion and an'angement of facts which, when so an-anged, 

 will tend to show causes and their effects and the laws of 

 nature, that we find a close approach to natiu"al science, as 

 defined by the illustrious author whose words have been 

 just quoted. Hence, the unportance of tracing the distribu- 

 tion of plants, as influenced by physical geography, includ- 

 ing the climate of coimtries. The facts of geogi'aphy, and 

 th*e facts of botany, are thus brought into relation, as proxi- 

 mate " causes and theu' effects ;" and we get so far ad- 

 vanced on oiu" way towai'ds ascertaining those " laws of 

 nature" which determine the floral productions of the eai-th, 

 or of any portion of its sm'face which may be more immedi- 

 ately under consideration. 



Still, be it remembered, we must begin with facts and the 

 arrangement of facts, as necessary preliminaries to the in- 

 vestigation of causes and laws ; and it is wished, m the pre- 

 sent volume, to keep to mere facts and their methodical 

 an'angement, as closely as the nature of the subject may 

 allow ; — causes and laws being resented for after considera- 

 tion. The nature of the facts which bear upon the an-ange- 

 ment of plants in Climatic Zones, will be made more clear, 

 by citing some examples of those changes in the flora wliich 

 ai-e seen while descending from the summits of high moun- 

 tains, into the vaUeys or glens below. 



In July of 1832, the wiiter of these pages ascended to 

 the summit of Ben-muich-dhu, the highest of the Grampian 

 moimtains, and the second (if not actually the loftiest) sum- 



