64 
Proceedings of the' Royal Society of Edinburgh, [Sessl 
off stringers here and there. The material has been mined to a depth of 
over 300 feet, and a vein has more than once been followed downwards till 
it breaks up into a network of fine stringers in argillaceous rock and finishes 
finally in a sandstone saturated with heavy, sticky petroleum. All the fine 
sandstone beds among the clays are more or less stained or impregnated 
with inspissated oil, and films of dried-up oil can be detected on joint and 
slip planes among the clays. There can be no doubt as to the origin of the 
veins; the manjak in a fluid or semi-fluid state has been forced under great 
pressure upwards from its source in the parent oil-sands below, and taking 
advantage of any plane of weakness has formed the main vertical veins 
S.E. N.W. 
Cora/ 
L/mes/one 
SCOTLAND SERIES 
Ocean/c 
Beds 
MANJAK Ue/ns 
Fig. 4. — Diagrammatic Section through a Barbados Manjak-Field. 
with their ramifying branches, and has gradually solidified and dried up 
or inspissated to its present condition. The manjak veins in Barbados all 
occur above the main oil-sands, and had there not been a practically im- 
pervious cover of argillaceous rock we may safely assume that there would 
be no veins of intrusive bitumen. 
2. Trinidad . — In the principal manjak-field in Trinidad, the San Fer- 
nando field, the structure is somewhat different. Here we are dealing with 
the southern lip of a large basin, the inclination of the strata decreasing from 
40° to horizontal as we proceed northwards. Along the southern lip of the 
basin there is an outcrop of oil-sand from which heavy inspissated oil can 
be collected in excavations. The strata above for some 800 feet are entirely 
TJl 
n ► i > 
C/ays 
rCC-Jmci O/ /sands 
