Conglomerates^ and Marls of Devonshire. 
38 
of false stratification) -|- 10° (dip of true stratification in the 
opposite direction). Subsequently much of this bed was destroyed, 
it being cut dovm to the level of f. — which it only retained, however, 
farther west than the point so marked — and to a still lower level 
further eastward. On the surface thus planed ofi", and of which 
c. f. is a portion, water moving towards the opposite direction, 
S. 70° E. (mag.), deposited similar material in stratula inclined 
at an angle of 13°=23° (dip of stratula)— 10° (dip of true 
stratification). On the completion of this, denudation again set in 
and produced an even sloping surface h.f. e., the slope, in fact, of 
the original stratula. This efiected, the water flowed again towards 
X. TO'' W., and diagonal stratification, agreeing in amount and 
dii-ection of dip with that first formed, was produced in the matter 
which it deposited. It is assumed in the foregoing explanation that 
the planes of stratification were originally horizontal. 
There can be no doubt that the operations just described absorbed 
a considerable amount of time, but it would appear that the various 
changes succeeded one another without considerable intervals or 
periods of intermittence, inasmuch as the sand seems to have 
remained incoherent throughout the whole, since the lines c. / and 
h f. e. are not more strongly marked than those which separate 
contiguous and conformable stratula. 
My friend Mr. Sorby exhibited to the Geological Section of the 
British Association, during the meeting at Cheltenham, in 1856, a 
" Working Model," which he had recently invented for the purpose 
of illustrating the phenomenon now under notice. The following is 
his description of the instrument. " In the model, the drifting effect 
of the current is intimated by a kind of coarse screw, which, when 
turned round, carried foi-ward the sand, supplied from a bag, along 
a groove, from which it fell into a space with a glass front, where it 
accumulated at the angle of rest. Being a mixture of heavy black 
fine grains of specular iron and coarser white quartz sand, it became 
sorted by moring the screw alternately quickly and slowly, and thus 
accumulated in black and white bands ; whereas if it was moved 
with a uniform velocity no such bands were producod, but the coarse 
white particles collected at the bottom."- 
There are certain remarkable appearances - in the coarser Sand- 
stones and verv' fine Conglomerates at Watcombe of which I can 
give no explanation, and which I fear it may be difficult to describe. 
In ordinary^ and unaltered sandstone the grains, or, more correctly, 
scales or plates of sandy matter are unequiaxed, and, as might be 
expected, lie with their shortest axes at right angles to the plane of 
sedimentation, so that their inclination to the horizon is the same as 
tkat of the bed or layer which they compose ; hence in either a 
llejjort Brit. Assoc., 1856, page 77. 
