AND PORTO SANTO. 5 



of Angola and Mozambique, when I learned that a Portuguese 

 schooner was on the point of sailing for JNIadeira, and having 

 safely deposited my instruments on board, with the exception of a 

 barometer, I hastened to devote the first day of leisure I had 

 enjoyed, to an excursion in the environs of the aqueduct. 



On the right of the descent to the aqueduct are large fragments 

 and rocks, presenting all the characters of transition limestone; 

 here crystaUine, there compact, equally variable in fracture ; and 

 the outer surface, exposed to the air for ages, passing through 

 all the different shades from red to black, and yielding with 

 difficulty to the hammer, which exposed the buff and white colours 

 pervading the interior of the mass. This fresh surface, where the 

 recent fall of vast blocks exposed it in considerable patches, formed 

 a pleasing contrast to the gloomy appearance which the moisture 

 of the atmosphere had induced over the rest. But few plants had 

 withstood the unusual dryness of the last summer; even the clefts 

 of the rocks were almost destitute of* them; and I was much 

 disajjpointed in my search for lichens and mosses, of which I 

 promised myself a rich harvest. To give some idea, however, 

 of the social plants which characterized the vegetation, I gathered 

 the cicJiorium intj/bus and the anagnllis arvensis, as I descended 

 to the small river, which, during the rainy season, flows under 

 the great arch of the aqueduct; and pursuing its bed for a sliort 

 distance, I found the veronica beccabunga, close to a dirty stream 

 and several tufts of the solamtm pubescens. 



Ascending from the little river by the garden of orange-trees, 

 and turning round to look to the eastward, or towards the city, 

 we are struck with the regularly-stratified appearance of the 

 lower range of the dingy hmestone of the opposite side ; looking 

 in many places like the coarse masonry of a vast fortress, while 

 the higher range, defaced as it were by the labours of the quarry- 

 men, seems hewn nito rude buttresses, and has lost all traces 



