RECORD OF DEEP-WELL DRILLING FOR 1905. 15 
WELL RECORDS. 
By Samuel Sanford. 
INTRODUCTION. 
The definition of a deep well is so variable in different localities 
that it has been difficult to determine where to draw the line in 
selecting logs for publication in the present report on deep-well drill- 
ing in 1905. In many localities a 100-foot well is regarded as deep, 
while in others 500 or even 1,000 feet is the limit fixed. Nor is the 
value of a record necessarily dependent on depth, the data of certain 
shallow wells being more important than those of many of the deeper 
ones. There are, moreover, a large number of drillers, especially 
those using light portable rigs for drilling domestic wells, who are 
interested in relatively shallow wells, for which reason the present 
report is made to cover all wells over 100 feet in depth. That shal- 
lower wells are not included does not mean that details of such wells 
have not been obtained, nor that they are not deemed worthy of 
record. The line is drawn as indicated because the number of records 
of shallow wells is so great as to prohibit their inclusion in a report 
primarily relating to deep wells. 
Many hundreds of records that have been obtained by the Survey 
during the past year are not published here, but are reserved for use 
in the preparation of special reports on particular districts where 
it is desired to present with the greatest exactness the relations of 
the underlying rocks or the depths to certain beds. Such records 
are of particular value in the preparation of the structural geology 
maps that appear in the various folios of the Geologic Atlas of the 
United States, many hundred logs often being collected and com- 
pared before the publication of a folio, especially in the case of 
those located in the oil and gas fields of Pennsylvania and other 
States. It is because of the omission of such records that so few 
wells from the more active districts, where the rock succession in 
many places is well known, are included. The object, on the con- 
trary, has been to present records from the scattering or so-called 
" wild-cat" wells drilled in new or little-known territory. 
ACKNOWLEDGMENTS. 
Thanks are tendered the following contractors and drillers who 
have assisted the Survey in its endeavor to secure information as to 
the strata penetrated in drilling and the economic results of the 
deep borings. To the interest they have shown and the pains they 
have taken in furnishing data whatever of value this work may have 
is chiefly due. 
