Vol. 50.] GEOLOGY OF MATTO GROSSO. 87 



(14) Poitljiann, Robert, 'Gesteine aus Paraguay,' Neucs Jahrb. 188G, vol. i. 

 pp. 244-248. 



(15) Derby, Orvili.e A., 'On Nepheline-Bocks in Brazil. [Pt. I.] Quart. Journ. 

 Geol. Soc. vol. xliii. (1887) pp. 457-473. 



(16) , ' On the Magnetite-Ore Districts of Jacupiranga and Ipaneina, Sao 



Paulo, Brazil,' Am. Journ. Sci. ser. 3, vol. xli. (1891) pp. 311-321. 



(17) , ' On Nepheline-Rocks in Brazil.' — Pt. II. Quart. Journ. Geol. Soc. 



vol. xlvii. (1891) pp. 251-205. 



e. Other papers referred to. 



(IS) Barbour, Erwin H., and Joseph Torrey, Junr., ' Notes on the Micro- 

 scopic Structure of Oolite, with Analyses,' Am. Journ. Sci. ser. 3, vol. xl. 

 (1890) pp. 246-249. 



(19) Van den Broeck, Ernest, ' Les Cailloux Oolithiques des Graviers Ter- 

 tiaires des Hants Plateaux de la Meuse,' Bull. Soc. Beige de Geologie, 

 vol. iii. (1889) pp. 404-410. 



(20) Whympbr, Edward, ' How to use the Aneroid Barometer,' London, 1891. 



(21) Gregory, J. Walter, ' The Physical Features of the Norfolk Broads,' 

 Natural Science, vol. i. (1892) pp. 347-355. 



III. Physical Features of Matto Grosso. 



Matto Grosso is the second largest of the Brazilian States. Its 

 area exceeds 2 million square kilometres 1 (about half a million 

 square miles). It is adjacent to Bolivia and Paraguay, and 

 holds as nearly as possible a central position in the South American 

 continent. 



The centre of the State is occupied by an undulating tableland, 

 rising in places to more than 800 metres (2600 feet) above sea- 

 level. 2 It extends from the south-west of the State of Goyaz in a 

 ■west-north-westerly direction to the cataracts of thellio Madeira, just 

 above its junction with the Bio Madre de Dios. The eastern 

 portion is called the Chapada, a name commonly applied in Brazil 

 to tablelands like this with precipitous sides. Farther west, the 

 steep southern margin is known as the Serra dos Parecis (from the 

 Indian tribe of that name) and the Cordilheira Geral. 



On the northern boundary of the plateau we find the bead- 

 waters of the Araguaya, Xingu, and Tapajos, which flow northward 

 into the Amazonas. The southern drainage is performed partly by 

 the Guapore, a tributary of the Madeira (which above the point of 

 confluence is known as the Marmore), and therefore of the Amazonas, 

 and partly by the numerous tributaries of the Upper Paraguay. 



This tableland is believed to sink more or less gradually to the 

 northward into the Amazonian plain, while on the south there is a 



1 The official unit of distance is the kilometre, but the Brazilian league of 

 6'6 kilometres (4T English miles) is often used. 



2 Calculations from the author's aneroid readings near the village of Sant' 

 Anna da Chapada gave a height of 880 metres or 28(>0 feet ; but no doubt some 

 deduction must be made from this estimate, on account of the progressh 8 changes 

 which Mr. Whymper has shown to take place in an aneroid when it is 

 under diminished pressure : see (20) p. 58. 



