8 ANNIYEESAEY ADDEESS. 



built. Whether tliese ranges do or do not form any outliers of 

 the long ridge of Soaves and Contendas, in Minas Greraes, those 

 that are depicted in Mr. Nicolay's map of Bahia may be con- 

 sidered as partly forming the versed sine of an arc of which the 

 Paraguaasu is the chord of a great segment formed by the lower 

 course of the Rio Erancisco. 



The general strike of the ranges varies from 'N.W. to N.E. ; 

 and the central portion occupied by the Districto Diamante is 

 that which is sometimes known as the Chapada Diamantina. 



The diamond region, which is traceable in other parts of the 

 territory between the great river and the sea, must have a wide 

 area. The country has not yet been thoroughly explored, and it 

 is partially covered by dense forests, as in the Mattas do Orobo. 



Mr. Hartt confirms Mr. Nicolay's statement as to the matrix 

 of the diamond in Bahia. He says, " From IMr. Nicolay's report, 

 as well as from what he has stated to me in conversation, there 

 can be no doubt that the diamonds of the interior of Bahia occur 

 in a sandstone bed, forming part of the great sheet which once 

 overspread the whole country, tying in with the sandstones and 

 clays of the Jequitinhonha basin ; and this sandstone, as we shall 

 see from INIr. Allen's report, is found at Jacobina, at which j)lace, 

 in 1755, diamonds were first discovered in the province of Bahia. 



" I saw specimens of the diamantiferous rock from the Chapada 

 in the hands of Mr. Nicolay. It was 7iot Itacolumite, but it 

 seemed to me to bear a very close resemblance to the sandstone 

 bed overlying the clays in the Jequitinhonha basin. It also bore 

 a close resemblance to the tertiary sandstones on the Bahia 

 Eailroad, near Pitanga, where diamonds also occur. The diaman- 

 tiferous sands I saw in the possession of Dr. de Lacerda, at 

 Bahia, appeared to have resulted from the disintegration of the 

 Chapada sandstones." 'Mr. Hartt continues : " It is much to be 

 regretted that the diamond mines of the Chapada Diamantina 

 have never been critically examined, but I feel convinced that, 

 from their study, the mystery of the origin of the diamond is to 

 be solved." {See Seientijic Mesidts ly Agassis, p. 307.) 



