LETTER OF TRANSMITTAL. xv 



quently, I liave not tVlt wM.Tauted in usiuj.- his luuue iu this g-eneral Avay 

 Chapter i he prepan-.l, with the exception of a few pages, and this is 

 cre.lite.I to hini: eha,p(ers ui, iv, an.l v were jointly prepared; the remain- 

 nig chapters have fallen upon nw. In ,,rder to make it perfectly clear to 

 what extent the work can have the shelter of Prof. Irving's authority, each 

 chapter is headed Ijy the name of its author. 



Very respectfully, your obedient servant, 



C. R. Van Hise, 



GeoIoijiM ill charge. 

 Hon. ,T. W. Powell, 



. Director U. S. Geolof/kal Survey, Washington, D. a 



