THE ANALYSES. 



23 



GROUPINGS AND CLASSIFICATIONS OF ANALYSES. 



As the volumes and relative proportions of the gases found in the fore- 

 going analyses vary within wide limits, the nature of this variation can 

 best be shown by grouping the results. To make these tables as complete 

 as possible, not only the results of the present studies, but all the available 

 analyses of other investigators, have been included in the lists. Except 

 in the case of four of the five analyses by Tilden, relative to which suffi- 

 cient data are not given, all of the figures in these tables refer to volumes 

 of gas per volume of rock. Previous investigators have usually given the 

 total volume of gas and the percentages of each constituent. From these 

 I have calculated the volumes for each individual gas. 



TABLE 9. Analyses classified by groups of rocks. 



