23 PREFACE 



The Maryland Geological Survey has enjoyed the cooperation of the 

 U. S. Geological Survey as in previous volumes. It is indebted to this 

 organization for the use of drawings illustrating Dr. Kindle's contribution. 

 Special acknowledgment is due to Dr. John M. Clarke for the loan of many 

 drawings first used in the classic volumes of the Xew York Geological 

 Survey. 



