(8 PROCEEDINGS OF THE AMERICAN ACADEMY. 



could be made before this reoxidation was needed. Regeneration of the 

 copper oxide was effected by drawing air through the apparatus while 

 hot. It was found that the copper oxide when once ioapreguated with 

 carbon dioxide while strongly heated could be reoxidized by an air current 

 with very little tendency to occlusion of air. After the passage of air 

 for a few hours, a stream of carbon dioxide readily expelled the remain- 

 ing air and the apparatus was again ready for further determinations. 

 But if the copper oxide was allowed to cool in contact with air, much 

 time was lost in removing the air by the current of carbon dioxide, even 

 wlien strong heat was applied during the process. It appears that little 

 or no occlusion of air takes j^lace when the copper oxide is first impreg- 

 nated with carbon dioxide^ while the same substance exposed to air in 

 the cold occludes the air and hoUls it with much persistence. 



Selection of Samples of Gas. 

 Many'of the wells are drilled through several different gas producing 

 sand rocks, separated by deep layers of impervious shales and other strata. 

 The gas from these different sands mingles, and tlie product flowing from 

 a single well is often a mixture of gas from formations many hundred 

 feet apart in the vertical scale. It was attempted as far as possible in 

 the present work to secure samples from wells yielding gas from a single 

 sand rock. It was desirable that the samples be taken as far as possible 

 from wells situated at no great distance from the laboratory, in order 

 that as short a time as possible should elapse between the collection of 

 the sample and the commencement of the analysis. 



Results of Determinations of Nitrogen. 

 1. Gas well at Shields, 14 miles west of Pittsburgh. This well was 

 drilled in 1892, and yields gas exclusively from the Fourth Sand, which 

 was reached in drilling at a depth of 1,7G0 feet. 



Date of Collection of Samples. Percentage of Nitrogen found. 



August 0, 1896 (1) 1.25 



(2) 1.26 



February 5, 1897 (1) 2.70 



(2) 2.67 



(3) 2.68 

 April 6, 1897 (1) 1.79 



(2) 1.80 



April 20, 1897 (1) 1.85 



(2) 1.85 



Junel, 1898 (1) 1.10 



(2) 1.10 



