LETTER OF TRANSMITTAL. 
Department of the Interior, 
United States Geological Survey, 
Washington, D. C. June 7, 1902. 
Sir: I have the honor to transmit herewith the manuscript of a 
paper on the Berea grit oil sand in the Cadiz quadrangle, Ohio, b} T 
W. T. Griswold, with recommendation that it be published as a Bul- 
letin, in the economic series. 
I believe that this paper marks a distinct advance in the methods of 
studying oil fields and of determining and delineating the structure of 
the oil-bearing formations. While it affords an exceptionally favor- 
able opportunity for subjecting the anticlinal theory of oil and gas 
accumulation to a rigid test, its primary object is to furnish practical 
information to the well driller. If the data contained in the paper 
are properly used in the field, a saving in expense of development 
will be effected amounting to many times the cost of the work done 
by the Survey. 
Very respectfully, C. Willard Hayes, 
Geologist in Charge of Geology. 
Hon. Charles D. Walcott, 
Director United States Geological Survey. 
9 
