1 865.] Draper on Petroleum. 55 



fast as if between the oblique sides of a narrow fissure. He shows 

 that from certain facts connected with their intermittence and occa- 

 sional interference with one another, the wells are often connected by- 

 channels more or less free, running, sometimes along the strata, some- 

 times across them. The productiveness of a well depends upon its 

 entering either one of the main reservoirs, or some of its important 

 connections. Every collection of oil is accompanied by varying quan- 

 tities of gas and water, the gas being above and the water below. The 

 material yielded by a well turns on the part of the cavity entered. If 

 it is pierced near the top, gas first escapes with violence, and subse- 

 quently, as water enters such cavities readily, the oil is floated to the 

 end of the boring, and may be pumped out. If, however, water enters 

 more quickly than the oil is removed, the latter may be floated to the 

 higher parts of the cavity, and be out of reach till the former is 

 pumped away. If the middle parts of the cavity are tapped, oil rises 

 at once in the well, forced up by the gas at the upper part, and may be 

 thrown out from the mouth of the well. This will continue till the 

 pressure of the gas is equal to the hydrostatic pressure of the column 

 of oil, when pumping out must be resorted to. If the lower parts of 

 the cavity are tapped, water at first will be the only product ; but if 

 this be pumped out, oil will at length be reached. It will rise in the 

 tube one-fourth higher than the water, on account of its less specific 

 gravity, *816, and thus a very unpromising well may prove productive. 

 The Shattuck well on the Little Kanawha had to be drained of water 

 with a steam pmnp for two weeks before oil was obtained, but after 

 that it yielded abundantly. 



In addition to this class of wells, which seem to consist of but one 

 isolated cavity, and which may be permanently exhausted, there is 

 another class in which the oil is more or less quickly replenished. 

 These are distinguished as intermittent wells, and where one is found, 

 it is a sign that there are many oil cavities near together in the same 

 locality. If it yields copiously for many months in succession, with- 

 out diminution in quantity, or increase in the intervals of yield, the 

 rocks in its neighbourhood may be presumed to contain rich supplies 

 of oil that may be directly reached. 



On Oil Creek, in Pennsylvania, most of the oil is found in the 

 same stratum of sandstone, the rock seeming to be perfectly honey- 

 combed with Petroleum cavities. The action of many of the wells is 

 as follows : — When oil is entered, the gas begins to raise it over the 

 top of the boring, increasing gradually in force till it projects perhaps 

 forty or fifty feet into the air, then alternately it increases and dimi- 

 nishes in force at regular intervals. These variations in the force of 

 the gas, or " breathings of the earth," as they are called, are explained 

 by supposing that, as the tension of the gas is relaxed by the removal 

 of oil, the gas and oil from other cavities rush in through the slight 

 fissures, until the maximum tension is again reached. A well may 

 alternate two or three times in a day, or as often in an hour ; it may 

 almost cease to yield, and then suddenly give out more than ever 

 before, owing to the bursting in of a new supply from some untouched 

 source, solicited by the decreased pressure. 



