PERU. 277 



reaching the wooded district of the Eastern slope of the Andes, yet 

 was very productive of results in the botanical department. 



The great difference of elevation, and the variation in climate con- 

 sequent thereon, would lead one to expect a greater variety in the 

 vegetation than was actually found. Forests were no where met with, 

 nor were any of the palm tribe seen ; very few of the many tropical 

 plants were perceived even on the coast. The smaller shrubs were 

 seldom found, except in the lower region, where their limit is circum- 

 scribed to the well-watered district. Thickets are very rare, and in 

 the higher regions appear to be "altogether wanting. The vegetation 

 of Peru on the whole is characterized by an air of tameness, indicating 

 but a slight change of season, and has been classed into four distinct 

 botanical regions, which are easily distinguished ; they will claim par- 

 ticular attention, and afford much interesting matter, in the Botanical 

 Report. 



The geological region passed over was also one of much interest, 

 and from the observations of the gentlemen, the following information 

 has been derived. 



The geological structure, as far as their observations went, cor- 

 responds to that of North Chili, with the exception of a narrow belt of 

 sedimentary rocks along the sea-coast, west of the granitic range, 

 which is wanting in that country. This belt includes the island of 

 San Lorenzo, and others, as well as the coast itself, to the extent of 

 from seven to ten miles from the sea-beach. These sedimentary 

 rocks are argillaceous, distinctly stratified, and more or less slaty, the 

 layers being in many places discoloured by the red oxide of iron. In 

 other places they appeared of a black colour, as if in the vicinity of 

 coal-beds, of which the existence was spoken of, but we did not dis- 

 cover any unequivocal traces of this substance. Some conspicuous 

 examples of faults were noticed by Mr. Dana, along the coast of San 

 Lorenzo. Many minerals were also found by this gentleman ; among 

 them gypsum was of frequent occurrence, as well as some fossils : for 

 fuller information, reference is made to the Geological Report. 



The hills and mountains to the eastward, joining the above sedi- 

 mentary rocks, are exclusively of granite, which extends in width to 

 the distance of forty-five geographical miles beyond Yaso. In places 

 it has very much the appearance of a stratified rock ; it is much broken 

 and variable in its character, so as to render it somewhat deceptive. 

 Dr. Pickering observes, that this peculiar character or appearance is 

 owing to the slow process of the decomposition of the rock in this dry 

 climate, and which would in other places, subject to the ordinary 



