9G l ORTON— ROCK PRESSURE OF NATURAJ GAS. 



Professor Orton says, a practical man estimates according to the pressure it 

 will attain in a minute. In the region contiguous to AJleghany county and 

 Washington they have about five producing horizons. They are all porous 

 sand rocks, and there is an increase in pressure with the depth such as rep- 

 resented by I' ! Orton's figures; bo that, where it is possible to gel any 

 data with reference to these wells, they seem to amply confirm his statements. 

 Dr. A. C Lawson: 1 understand thai Professor Orton has suggested the 

 possible connection between the pressure of 600 feel of sail water and the level 

 ■ it' Lake Superior. I would ask whether that figure represents a horizontal 

 plane in the earth's crust, or whether it has a slope from 600 feel down to 



zero? 



Professor Orton: So far as my observation goes, in Michigan. Indiana 

 and Ohio, the surface of the salt water is a horizontal plane. The water 

 doe.- not always rise promptly, but give it time and it rises to the level already 

 named. For example, a deep well has lately been drilled in Erie, Pennsyl- 

 vania, and salt water, apparently derived from the Trenton limestone, has 

 risen from a depth of about 3,000 feet to the lake level. 



Dr. Lawson : I would like to ask the extent to which capillary attraction 

 in the rocks raises salt water in the column above the sea level ? 



Professor Ortox : I would not presume to answer that, but this factor is 

 taken out of the account, from the presence of the impervious shale that 

 makes in all cases the cover of the gas rock or oil rock and that prevents 

 the a.-cent of the salt water; and it i> the penetration of this cover that 

 gives us our first ace-- to the gas, oil, and water that are contained in these 

 porous rocks. 



Mr. W J McGee: A few months ago 1 had occasion to make a study of 

 the Indiana gas held. Fortunately I was acquainted with Professor Orton's 

 work in Ohio, and not only made use of the theory which he has so well 

 developed, but was able to fortifyit by a large number of observations (made 

 chiefly by a collaborator of the I . S. ' Seological Survey, I )r. A. .1. Phinnej 

 in my hands at thai time; so I can supplement Professor White's remarks 

 b\ Baying that this theory explains in a satisfactory manner the phenomena 

 displayed by all the gas fields of Indiana— those of the great central field 

 and those of tnosl of the .-mailer outlying fields as well. 



I desire to add a more general tribute to the excellent work recorded in 

 Professor Orton's communication. In my judgment, the most important 

 advance .ver made in economically applied geology in a brief period was 

 that made within the last three years in the United States. Three years ago 

 k gas with all it< phenomena was a mystery t" the geologist a- well a- to 

 the layman, and the geologisl W unphl.lv in the dark a- the prospector 



concerning the origin of tie mcerning the law- of its distribution, con- 



ning the cause of the rock pressure, and concerning other important qui 



