vu by Dr. 

 bird] J, so 



C. F. Hartt— Geological Survey of Brazil 467 



metal of the lower portion in this part of the vein. Action of 

 this nature was first demonstrated bj Dr. James E. Mills in the 

 auriferous district of Rio Grande do Sul and has been confirmed 

 by the observations of Viscount de Barbagena in his mineral- 

 ogical studies of the auriferous gneiss of Minas Geraes. 



Secondly, the gold occurs in the lower part of a deposit of 

 red earth, which covers the whole surface of this region. This 

 is a mechanical mixture of the ingredients of the decomposed 

 gneiss, the local origin of which is not perfectly evident. All 

 parts of the earth are not equally rich, and the gold is proba- 

 bly distributed in some relation to the outcrops, as has been 

 ' "^ . Mills in the eastern part of the province, 



! gold is found in the alluvial deposits of the 

 river-valieys, and in the vicinity of the ancient excavations of 

 Sao Gon9alo and Campanha ; the abundant " waste" also con- 

 tains a considerable quantity of the metal. 



Notwithstanding the small amount of gold and the fact that 

 the richer deposits have already been extensively washed, this 

 section appears to be worthy of scientific study, and, probably, 

 by the application of methods similar to those employed in tiie 

 California ^/acers, the region may yet become productive. To 

 this end are required the detailed exploration of this part of 

 the country, the limitation of claims and the introduction of a 

 cheap method of extraction. A survey of the character men- 

 tioned will probably be soon made. 



Last year, Dr. Mills spent about six months in the study of 

 the auriferous region of Minas Geraes, where he succeeded in 

 discovering and applying the law of the distribution of gold, 

 especially of its occurrence in the series of rocks characterized 

 by the presence of itacolumite,Si law extremely important 

 in its bearing upon the future development of the resources of 

 that province. This gentleman has promised to give me a 

 complete report, in which he will not only enunciate and illus- 

 trate this law, but will also include all the scientific results of 

 his interesting explorations. 



For several years past I have been engaged in the systematic 

 examination of the border of the Brazilian plateau for the pur- 

 pose of discovering and critically studying the different geo- 

 logical formations, which are there better developed and more 

 fossiliferous than in the interior, being convinced that I could 

 thus most quicklv obtain a sure basis for the study of the gen- 

 eral geology of the country. Having received instructions for 

 continuing those studies by beginning in the northern provinces 

 and proceeding southward, I judged it best to inaugurate the 

 labors of the Commission by the exploration of the coast of 

 Pernambuco. On the 10th of July [1875] I left Rio for that 

 province, accompanied by Drs. Jordao and Freitas, and Senhor 



