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KIRTLEY F. MATHER 
result in the present connection is the downward migration of 
oil from the extremely small pores between the mud particles 
to the larger interstices between the sand grains, which had 
previously been filled with water. 
In McCoy’s second experiment, a layer of wet sand was ar- 
ranged in the form of an anticline between two layers of oil 
saturated mud. The sand grains near the crown of the artificial 
anticline were small, all passing a 40 mesh sieve, while those on 
the limbs were coarser, none passing a 10 mesh sieve. The top 
of the rectangular glass box containing the three layers was 
sealed with paraffin and water allowed to enter through openings 
at the lowest horizon of the sand, but was kept at a level below 
the top of the curve in the sand. Water entered the mud both 
above and below the sand layer, and replaced about an inch of 
the oil in the mud. The displaced oil moved into the interstices 
between the coarser grains of sand and within 24 hours there was 
an ^‘oil pool” in both limbs of the anticline on either side of its 
water-filled crest. These results could not have been effected 
by simple capillary pressure such as that operative in the Dau- 
bree experiment because the spaces between sand or mud parti- 
cles were occupied with either oil or water and the paraffin seal 
over the top of the box prevented evaporation. There were, 
however, certain forces at work which drove oil out of small 
openings into large ones and at the same time drew water from 
the larger to the smaller pores, regardless of the direction involved 
in the transfer or of the tendency of oil to float on top of water. 
In many of Mills’ experiments, coarser sands were used, and 
water circulation, sometimes under considerable head, was in- 
volved. • Few of them afforded much opportunity for capillary 
action to display itself. Nevertheless, capillary adjustments 
seem to have occurred between oil and water in saturated strata. 
These, states Mills, are restricted within short lateral ranges, 
amounting to only a few centimeters in his experiments. His 
conclusion was that the principal role of capillarity, in saturated 
strata, is to retard rather than to promote fluid movements. 
