IV 
Penck and Dr Juan Rassmuss, where ancient metamorphic rocks ana- — 
logous with them of the Sierra de Umango are the predominant. 
The present paper is a somewhat modified edition or rather a working ‘ 
up in english of my original spanish report, addressed to the Direction of 
Mines, Buenos Aires. The later will be printed in the Bulletin of the 
Direction (Serie B, Geologia). 
I am much obliged to the Direction of Mines and especially to the ~ 
Director General, Engineer E. Hermitte, for the obtained permission to 3 
publish this memoir in an independent way. ; 
Academy of Åbo, Finland. September 1921. 
