Mr. Gardner on the Existence of Chalk in Braxil. 147 



colour, often with a grey tint The predominant constituent parts of 

 this marl, as it is termed, are described as silica and iron. But the 

 greatest resemblance which exists between this ferruginous sand forma- 

 tion and the cretaceous rocks of Europe, is the similarity of their fossil 

 remains. Dr. Morton has found it to contain the characteristic fossils 

 of the chalk, particularly Bacculites and ScaphiteSy together with 

 Ammonites, Belemnites, Echinites, the Mososauris, and Plesiosaunu, 

 also univalve and bivalve shells of the same epoch. Among the latter 

 is the well-known Pecten 5-costatus, one of the most widely-distributed 

 cretaceous fossils. 



It is asserted by Humboldt that neither oolite nor chalk exist in 

 South America, from the fact that no traveller who has hitherto written 

 on the geology of that immense continent has met with either. The 

 southern, like the northern continent, has now been pretty extensively 

 explored. Humboldt himself made extensive journies on the western, 

 and central parts of its northern extremity ; and the same has been 

 done more recently on the eastern side by Schomburg. The chain 

 of the Andes southward has been examined by Col. Hall, Pentland, 

 my friend Mr. Miers, Caldcleugh, Gilles, Poepig, Darwin, and others. 

 And if we turn to the eastern and central parts of the continent, we 

 will find that they also have been extensively traversed. The southern 

 portions have been well examined by Darwin, Miers, and Caldcleugh. 

 The southern provinces of Brazil have been carefully explored by 

 Spix and Martius, whose travels extended through the central parts 

 of Brazil northward to the district of the Rio Negro, situated between 

 the Amazon and the Oronoco. The mining districts have also been 

 well explored by them, as well as by Von Eschwege, and our country- 

 man Maw. Langsdorf, Burchel, and St. Hilaire, also made extensive 

 journies in the interior of Brazil ; and my excellent friend, M. Riedel, 

 the botanist who accompanied Baron Langsdorf, crossed the whole 

 Brazilian empire in a north-west direction to the boundaries of Bolivia, 

 and finally, like Poepig, descended the Amazon to Parlu But by none 

 of these travellers were any traces of the chalk formation detected. 



My own excursions during upwards of five years of nearly incessant 

 travel extended over a vast tract of the Brazilian empire. Although 

 my principal object was to make botanical collections, zoology and 

 geology were not neglected. My geological observations, I may men- 

 tion, have extended along nearly the whole coast from the equator to 

 the southern tropic ; and, inland, from two degrees of south latitude, in 

 a south-west direction, nearly to the western extremity of Brazil, and 

 from thence in a south-east direction through the diamond and gold 

 districts to Rio de Janeiro. The northern provinces of Brazil had 

 hitherto been the least visited by naturalists — indeed several of them 

 of great extent had never been visited at all. These, therefore, I was 

 the most anxious to explore ; and riclily have I been rewarded by the 

 ^umerous new plants which I found there, and by the discovery — for 



