"2 '34 J. C. BEAXXER OUTLINES OF THE GEOLOGY OF BKAZi^ 



try. and Commerce. The director from IS To to 1S91 was Dr. Henri 

 Gorceix: the present director, who succeeded Dr. Gorceix in 1S91. is Dr. 

 J. C. Costa Sena, a native of Minas Geraes and a graduate of the school. 



In this connection should be mentioned the establishment of the "An- 

 naes da Escola de Minas."' in which have appeared many valuable contri- 

 butions to the geology and mineralogy of Brazil by the professors and 

 students of the school. Fourteen numbers or volumes have been issued. 



The state began a geological and topographical survey in 1S92. under 

 the title of Commissao Geographica e Geologica de Minas Geraes. Work 

 was carried on until October. 1S9S. when it was suspended.'- The fol- 

 lowing ten topographic sheets were published by this survey on a scale of 

 1 to 100.000. with 50-meter contours : Ayuruoca. Baependy. Barbacena. 

 Carrancas. Ibertioga. Lavras. Lima Duarte. Luminarias, Eio Preto. and 

 Sao Joao d'el Eei. Besides these topographic sheets the commissao pub- 

 Kshed reports of progress which appeared in the form of five bulletins be- 

 tween 1892 and 1898. A geological sheet was prepared for publication in 

 1899, but before it could be issued the survey was suspended. 



On the geology proper the following writers are noteworthy : Eschwege, 

 Gorceix, Helmreichem Pissis, Leith. Harder, and Chamberlin. In addi- 

 tion to the reports of progress of the Commissao Geographica e Geologica, 

 valuable geologic notes made on trips through the state are those of 

 31. A. E. Lisboa, Francisco de Paula Oliveira. J. C. da Costa Sena. An- 

 tonio Olyntho. and 0. A. Derby. 



Special mention should be made of the work done by Horace E. Wil- 

 liams, of the Service Geologico do Brazil, in northwestern Minas between 

 south latitude 18° 30' and 21"", and between west longitude 45° and 48°. 

 The results of Mr. TVilHams' excellent work on this area have been sent 

 me. but unfortunately they reached me too late to be incorporated in the 

 map. 



General geology. — Archean rocks cover a larger area in the state of 

 Minas than any other one division of the geologic column. They are 

 exposed over nearly all of the southern and eastern parts of the state, 

 occupving an area of 266,600 square kilometers out of a total state area 

 of about 580.000 square kilometers. Included in this Archean area, how- 

 ever, is the old Paleozoic series mentioned in the following paragraph. 



Thrust-faulted into the Archean are certain old metamorphosed Paleo- 

 zoic rocks that now appear as quartzites. schists, itacolumites. marbles, 

 and as iron and manganese ores. These infaulted areas are often small 



■ The follo^ring were directors at different periods : 

 Augusto de Abreu Lacerda. 1S92 to lS9o. 

 Alvaro da Silveira. 189.5 to 1898. 



