In a previous paper some evidence was presented to account for the changes in the composition of petroleums with age and depth, by the action of active-surface catalysts. In 1934, D. C. Barton published graphs based on United States Bureau of Mines analyses of petroleums from Gulf Coast fields. Barton's graphs for the Gulf Coast Miocene, Oligocene, and Eocene oils indicated progressive change in composition with age and depth, the older and deeper oils having larger percentages of light constituents and less heavy residue. Barton's graphs did not show points corresponding with the composition of the oils considered in preparing the graphs. In the present paper, analyses of Gulf Coast oils are plotted, including the composition of oils discovered since Barton's work in 193 , together with many produced at depths not yet reached at that time.

The results shown in the present paper disclose that the regularity in change with age and depth is not as uniform as was indicated by Barton's graphs and, although many irregularities are evident, the average results show a general tendency which is in agreement with Barton's conclusions.