42 CHARLES DARWIN 



ant excursions in the neighbouring country. One day I went 

 to the Botanic Garden, where many plants, well known for 

 their great utility, might be seen growing. The leaves of the 

 camphor, pepper, cinnamon, and clove trees were delight- 

 fully aromatic; and the bread-fruit, the jaca, and the mango, 

 vied with each other in the magnificence of their foliage. 

 The landscape in the neighbourhood of Bahia almost takes 

 its character from the two latter trees. Before seeing them, 

 I had no idea that any trees could cast so black a shade on 

 the ground. Both of them bear to the evergreen vegetation 

 of these climates the same kind of relation which laurels 

 and hollies in England do to the lighter green of the decidu- 

 ous trees. It may be observed, that the houses within the 

 tropics are surrounded by the most beautiful forms of vegeta- 

 tion, because many of them are at the same time most useful 

 to man. Who can doubt that these qualities are united in the 

 banana, the cocoa-nut, the many kinds of palm, the orange, 

 and the bread-fruit tree? 



During this day I was particularly struck with a remark 

 of Humboldt's, who often alludes to " the thin vapour which, 

 without changing the transparency of the air, renders its 

 tints more harmonious, and softens its effects." This is an 

 appearance which I have never observed in the temperate 

 zones. The atmosphere, seen through a short space of half 

 or three-quarters of a mile, was perfectly lucid, but at a 

 greater distance all colours were blended into a most beauti- 

 ful haze, of a pale French grey, mingled with a little blue. 

 The condition of the atmosphere between the morning and 

 about noon, when the effect was most evident, had under- 

 gone little change, excepting in its dryness. In the interval, 

 the difference between the dew point and temperature had 

 increased from 7°-5 to 17 0 . 



On another occasion I started early and walked to the 

 Gavia, or topsail mountain. The air was delightfully cool 

 and fragrant; and the drops of dew still glittered on the 

 leaves of the large liliaceous plants, which shaded the stream- 

 lets of clear water. Sitting down on a block of granite, it 

 was delightful to watch the various insects and birds as they 

 flew past. The humming-bird seems particularly fond of 

 such shady retired spots. Whenever I saw these little crea- 



