1879.] - ltJ L [Derby. 



one volume of which was exhibited, and the other promised 

 in August next. 



The meeting was then adjourned. 



The Geology of the Diamantiferous Region of the Province of Parana, 

 Brazil. By Orville A. Derby, M. S. {English Version.) 



(Read by permission of the Director of the Brazilian Museum before the 

 American Philosophical Society, May 16, 1879.) 



A portion of the ancient Capitania of Sao Paulo, now the province of 

 Parana, has long been known to be diamantiferous, but as no extensive 

 washings have ever been undertaken, and as the gems thus far found have 

 been of small size, although of good quality and color, only very little 

 attention has been attracted to this region, in comparison with the more 

 fully explored diamond fields of the provinces of Minas Geraes and Bahia. 

 During a recent excursion in Parana, I was able to make some observations 

 on the geology of the region in question, and on the mode of occurrence of 

 the diamonds. 



The province of Parana lies between Sao Paulo on the north, and Santa 

 Catharina and Rio Grande do Sul on the south, and extends from the 

 Atlantic to the river Parana, occupying about six degrees of longitude and 

 three of latitude. Topographically it is divided into two very distinct 

 regions : a mountainous region along the coast, extending about 100 miles 

 inland, and a plateau region, occupying the central and western portions 

 of the province. The first or mountainous region constitutes a distinct 

 geological area, while the plateau portion is divided into two grand geologi- 

 cal provinces. Strictly speaking, the whole province, with the exception 

 of a coast belt from ten to twenty miles wide, is a plateau, the coast moun- 

 tains, constituting a part of the great Serra do Mar system, but known in 

 this province by the beautiful and appropriate name of the Serra Graciosa, 

 rising abruptly from the coast belt, and forming the margin of a plateau, 

 from 800 to 1000 metres in height. In the northeastern part of this great 

 plateau, an interior range of mountains, a continuation of the Parana- 

 piacaba range of Sao Paulo, rises above the general level, but dies away 

 towards the south. The coast belt, the Serra do Mar, and the eastern por- 

 tion of the great interior plateau, whether mountainous, as in the north, 

 or nearly level, as in the south, have the same general geological charac- 

 ters, and may properly be united together in what I will designate as tin- 

 first or mountainous or, geologically speaking, the metamorphic region. 

 The topography of this region, in the more mountainous portions, is bold 

 and abrupt, with picturesque peaks, rising to a height of about 1500 metres 

 above the sea, and 600 to 700 metres above the river valleys and the more 

 level portions. The latter are, in general, moderately undulating prairies, 



