THE ORIGIN AND DURATION OF PETROLEUM. 273 



yielded such abundance for a while and then become dry. But if 

 this theory is correct it does not follow thab the drying of such a well 

 proves a final stoppage of the supply, for if the cavity and crevice are 

 left, more oil may ooze into the crevice and flow into the cavity, and 

 this may continue again and again throughout the whole oil district 

 so long as the surrounding feeders of permeable strata continue satu- 

 rated, or nearly so. The magnitude of these feeding grounds may 

 far exceed that of the district wherein the springs occur, or where 

 profitable wells may be sunk, seeing that the localizing of profitable 

 supply depends mainly on the stoppage of further oozing away by 

 the action of the impermeable barrier. 



A well sunk into the oozing strata itself would receive a very small 

 quantity, only that which, in the course of its passage came upon the 

 well sides, while at the junction between the permeable and imper- 

 meable rocks the accumulation may include all that reached the 

 whole surface of such junction or contact many square miles. 



To test this theory thoroughly it would be necessary to make bor- 

 ings, not merely at the wells, but in their neighborhood, where the 

 porous rocks dip toward the limestone, and to bring up sample cores 

 of these porous rocks, and carefully examine them. Dr. Sterry Hunt 

 has done this in the oil-yielding limestone rocks of Chicago, but not 

 in those of the nearest coal-measures. 



As the oil industry of America is of such great national impor- 

 tance, an investigation of this kind is worthy of the energies of the 

 American Government geologists. It would throw much light on the 

 whole subject, and supply data from which the probable duration of 

 the oil supply might be approximately calculated. 



Such an investigation might even do more than this. By proving 

 the geological conditions upon which depend the production of petro- 

 leum springs, new s.ources may be discovered, just as new coal-seams 

 have been discovered, in accordance with geological prediction, or as 

 the practical discovery of the Australian gold-fields was so long pre- 

 ceded by Sir Roderick Murchison's theoretical announcement of 

 their probable existence. 



When the "kerosene wells" were first struck, the speculations 

 concerning their probable permanency were wild and various. Some 

 maintained that it was but a spurt, a freak of nature limited to a 

 narrow locality, and would soon be over ; others asserted forthwith 

 that American oil, like everything else American, was boundless. 

 Neither had any grounds for their assertions, and therefore made 

 them with the usual boldness of mere dogmatism. 



Then came a period of scare, started by the fact that wells which 

 at first spouted an inflammable mixture of oil and vapor high into 

 the air soon became quiescent, and from " spouting wells" became 

 " flowing wells," merely pouring out on the surface a small stream at 

 first, which gradually declined to a dribble, and finally ceased to flow 

 at all. Even those that started modestly as flowing wells did the 

 latter, and thus appeared to become exhausted. 



This exhaustion, however, was only apparent, as was proved by 

 the application of pumps, which drew up from wells, that had ceased 

 either to spout or flow, large and apparently undiminishing quanti- 

 ties of crude oil. 



Further observation and thought revealed the cause of these 

 changes. It became understood that the spouting was due to the 



