20 RECORD OF DEEP WELL DRILLING FOR 1904. [bull. 264. 
IMPORTANCE OF RECORDS TO GEOLOGISTS. 
To the geologist records are of value from both the practical and 
the scientific standpoints. Problems are submitted almost > daily by 
drillers and by present or prospective well owners in regard to the 
occurrence of oil, gas, or water. Where he can visit the field he can, 
as already indicated, work out the general features of structure and 
character and thickness of beds, and can make certain generalizations 
as to the occurrence of water and in some cases of oil and gas; but he 
can not give more precise information without a knowledge of the 
changes which the beds undergo beneath the surface, and these are 
best afforded by well sections. 
The occurrence of oil and gas is shown, as accurate investigation 
proceeds, to be more and more dependent upon structure, which term 
is here used in a broad sense to include both the attitude of the rocks 
and the changes in extent, thickness, or texture which they may 
undergo from point to point, and the same holds to an even greater 
extent in regard to artesian waters. Combining wejl records with sur- 
face observations, the geologist is able to locate the anticlines, synclines, 
flats, etc., so important in their bearing on the occurrence of oil and 
gas, to determine similar structures governing the occurrence of arte- 
sian waters and regulating their head, to predict the character of the 
material to be penetrated, to fix the depth of the producing horizon, 
and in the case of water to estimate the approximate volume to be 
obtained. 
From the scientific standpoint records and samples, especially where 
the latter include fossils, aid the geologist to a better understanding 
of the age and succession of the rocks, assist him in the correlation of 
identical or equivalent beds in remote localities, and enable him to 
work out the details of structure and history, all of which furnish a 
basis for conclusions which are of much benefit to the driller or well 
owner. 
WORK OF COLLECTING WELL RECORDS AND SAMPLES. 
ORGANIZATION. 
EARLY COLLECTION OF RECORDS. 
Ever since the organization of the Survey the collection of records 
as an aid to the study of geology has formed an incidental part of the 
work of the geologist in the field, but since the beginning of the pre- 
cise stratigraphic and structural work of recent years the collection 
of records has become an important part of the Survey's work in cer- 
tain regions. The vast majority of wells, especially in Pennsylvania, 
were sunk a number of years ago, but fortunately many records have 
been preserved. These were carefully collected by the geologists in 
the individual localities. 
