Recording drilling time manually has been fairly successful, but the method allows the human element to enter largely into the accuracy of the data. The information has been restricted chiefly to the depths where production is expected, and of course has not been kept for most rotary operations.

The geolograph is an instrument which automatically records the rate of penetration, foot by foot, along with such related information as time out for repairs, round trips, et cetera. A diagram of the hook-up illustrates the manner in which the motion of the tools is recorded. A chart form depicts the typical drilling changes in rates of penetration together with the information as to when the tools are on bottom, when drill-pipe connections are made, samples circulated, et cetera.

The geolograph was conceived by the writer and developed in cooperation with the engineering department of the Indian Territory Illuminating Oil Company. Its success

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has led to use as standard equipment on all this company's operations. The instrument is recommended as a geologist's tool as the record is subject to gross misinterpretation if studied apart from well samples and knowledge of geology of the areas involved.