1880.] "lit/ [Ashburner. 



ford Oil Sand of McKean county, Pennsylvania. Remarks 

 were made by Dr. Rogers and Mr. Lesley. 



Prof. Frazer exhibited his microscopic reflector, made by- 

 Mr. Zentmeyer. 



Mr. Frazer then discussed the principles of the problem 

 of the popular 15 number puzzle with Mr. Briggs. 



Pending nominations Nos. 893 to 897, and new nomina- 

 tions Nos. 898 to 901 were read. 



On motion, the subject (postponed from the last meeting) of 

 appointing delegates to assist at the Centennial Anniversary 

 of the American Academy of Science and Art, at Boston, 

 was referred to the President, Mr. Fraley, with power to act. 



And the meeting was adjourned. 



On the Constitution of the Bradford Oil Sand. By Chas. A. Ashburner, 

 3LS., Asst. Second Geological Survey of Pennsylvania. ( With a plate.) 



(Bead before the American Philosophical Society, March 5, 1880.) 



The constitution of the petroleum sands of Western Pennsylvania, which 

 were discovered in Venango county twenty-one years ago, and which 

 have ever since been producing mineral oil, is no doubt familiar to most of 

 our geologists. The question suggests itself ; in what way is the Bradford 

 sand of McKean county, Pennsylvania, and Cattaraugus county, New 

 York, dissimilar? 



Before describing the structure of the sands, permit me to give some 

 general facts showing the relative per centage of dry holes and the out-put 

 of the producing wells in the two districts. At a glance, the comparison 

 will indicate that some essential differences must exist in the sands and 

 mode of occurrence of the oil, to account for the different results which 

 have been obtained. 



During the year 1879, there were 475 wells drilled to the Vemmgo oil 



