gas have been observed throughout the whole extent of the area with which we are dealing. The 
value of such surface evidences is very great indeed. I know of very few oilfields the development 
of which has not been due either directly or indirectly to their presence. Some American oilfields 
have been quoted as showing no surface evidences, but in many of these cases outcrops of beds 
of the same geological age as those which were known to underlie these areas have contained sands 
which were impregnated to some extent with petroleum compounds or limestones which contained 
bitumen, and though these outcrops may occur at considerable distances from the developed 
oilfields, they have in large part given a clue the following up of which has led to the discovery 
of commercial supplies of oil. However, it cannot be denied that discoveries have been made 
without the known existence of such clues, though they have not been so numerous as some people 
believe. Everybody who makes use of petroleum products knows how quickly they discover 
any weaknesses in a containing vessel and show their presence on the outside. In nature it is the 
same. The petroleums take advantage of any flaw in the beds which contain them. They often 
show themselves on the sides of igneous rocks which have pierced the beds. Sometimes such 
igneous rocks will pick up a certain amount of petroleum in passage through the strata. Lines 
of fracture, such as those formed by faults, and strongly developed joint planes often liberate a 
certain amount of oil, especially where water is escaping also. Again, where strata containing 
oil are tilted so as to form what are called monoclinal folds, or where an anticline is deeply eroded 
at its crest, the sands which contain oil at depth may be exposed at the surface and give some 
indication of their nature, either by allowing seepages of oil to exude or by being impregnated 
with dark asphaltic or tarry matter where the oil is asphaltic in character, or with lighter-coloured 
paraffins where the oil has the paraffin type of base. The latter are sometimes difficult to detect 
since the rock may be discoloured very little and possess only a very faint odour on being broken. 
However, even in this latter case the experienced prospector is usually able to detect the nature 
of the sand. Outcropping tar sands are not at all uncommon. They are known in many places 
in the United States and Canada, while beautiful examples exist in Europe also, some not at all 
connected with any producing field at present. The best examples of outcropping paraffin sands 
T know of exist in Macedonia and in the Andes, in South America. It may be objected that in the 
case of strata having a very low angle of dip frictional resistance would prevent the oil from 
migrating up the dip for such distances as would be required for it to reach the surface, but in 
actual field work 1 have seen such beds impregnated with petroleum where the strata were almost 
horizontal. Now these Walloon strata lie in the form of a low monoclinal fold dipping of! north 
of Roma to the south or south-east at from 40 to 50 feet to the mile. Their edges must all come 
to the surface between Roma and a little distance north of Injune, but no evidences of the presence 
of petroleum have been found in any of the exposures that have been so far examined. Two 
conditions may exist to prevent any observable oil content being present in these outcrops. First, 
it is just possible that oil may be locked in by the lenticular nature of these deposits. Secondly, 
some of these sands are considered to be the intake beds for the water supplies that exist in the 
great artesian basins, and it is possible that the constant drainage of water down the dip of the 
sands has either washed down any traces of oil which may have existed or may have prevented 
it from migrating to the surface. 
Another feature of the case must be considered. The Walloon strata are a fresh-water 
series, and until recently this type of deposit was considered to be and had been found unfavorable 
to the formation of oil in commercial quantities. Prof. Scbuchert,* a well-known American 
geologist and author, has classified under the heading of “ The Impossible Areas for Petroliferous 
Rocks 
Practically all continental or f resit water deposits, relic seas, so long as they are partly salty, and saline lakes 
are excluded from this classification. 
But within the last five or six years certain types of fresh water deposits have been found to contain 
appreciable quantities of oil, and several good fields have been opened up along the eastern flanks 
of the Rocky Mountains. What are the conditions, therefore, that have been found to be necessary 
before fresh water formations can be expected to contain paying quantities of oil ? In the Rocky 
Mountain foothill region referred to the indications suggest fairly deep water conditions involving 
the accumulation of dark-blue carbonaceous shales in beds approaching 1,000 feet in thickness 
and permitting of fresh water limestones to be found at depth also. On the other hand, it must be 
noted that marine beds of Carboniferous age underlie the fresh water series, and these Carboniferous 
beds have not only been proved to contain oil in this region, but have been a prolific source of 
oil throughout the Mid-Continent oilfield area. Thus the possibility that the oil may have migrated 
into the fresh water series from the underlying marine Carboniferous formation can not altogether 
be overlooked. 
* Petroliferous Provinces. Discussion of 1C. Q. Woodruff's Paper. — Trans. Am. Tnst. Min. Eng., Chicago Meeting, 1019. 
