114 
SOUECE OF THE BITUMEN. 
It is idle to speculate on the ultimate source of the asphaltum. The generally attributed 
source, namely, a deposit of fossil vegetable matter, overheated *by volcanic rock, does not 
occur here apparently. The strata through which it escapes are, where observed, almost 
destitute of vegetable matter; the brown sandstone wholly, and the greenish having a few 
traces of fucoids scattered sparingly throughout their structure. The tertiary rocks are in 
contact with the granite. The sedimentary strata are hut a few hundred feet thick before primary 
rock is met with. There are no palasozoic strata, no extensive beds of metamorphic shale, no car¬ 
boniferous strata, to fall hack upon to hypothecate its formation. There are no excessive fish 
remains whose decomposition could he supposed, even hy a chemical imagination, capable of 
producing this mineral. 
Illustrations of the relation of asphaltic effusions to the contiguous strata are given in plate 1, 
figure 2, plate 4, figures 3, 4, and 6, and plate 5, figures 2 and 3. 
