DIFFERENT GRADATIONS OP 



waich, in mountain scenery, renders at times every outline 

 dim and indistinct, when scrutinised by reasoning on the 

 cause of the phenomena, may be clearly viewed and correctly 

 resolved into separate elements, to each of which its own 

 individual character is assigned ; and thus, in the study of 

 nature, as well as in its more poetic description, the picture 

 gains in vividness and in objective truth by the well and 

 sharply-marked lines which define individual features. 



Not only is the torrid zone, through the abundance and 

 luxuriance of its organic forms, most rich in powerful im- 

 pressions, it has also another advantage, even greater 

 in reference to the chain of ideas here pursued-, in the 

 uniform regularity which characterises the succession both 

 of meteorological and of organic changes. The well-marked 

 lines of elevation which separate the different forms of 

 vegetable life, seem there to offer to our view the inva- 

 riability of the laws which govern the celestial move- 

 ments, reflected as it were in terrestrial phenomena. Let 

 us dwell for a few moments on the evidences of this regu- 

 larity, which is such, that it can even be measured by 

 scale and number. 



In the burning plains which rise but little above the level 

 of the sea, reign the families of Bananas, of Cycadeae, and of 

 Palms, of which the number of species included in our floras 

 of the tropical regions has been so wonderfully augmented 

 in our own days by the labours of botanic travellers. To 

 these succeed, on the slopes of the Cordilleras, in mountain 

 valleys, and in humid and shaded clefts of the rocks, tree 

 ferns raising their thick cylindrical stems, and expanding 

 their delicate foliage, whose lace-like indentations are seen 

 against the deep azure of the sky. There, too, flourishes 



