
_ 
Parr lJ _ FALSE-BEDDING. ATT 
fissility may be recognized among rocks. Ist, lamenation of original 
deposit, which has just been described; 2nd, cleavage, as in slate; 
3rd, foliation, as in schists. Occasionally, by the development of 
steam-holes or spherulitic concretions in lavas, and the drawing out 
of these into planes during the movement of the molten mass, a 
kind of fissility is produced which at first might be mistaken for 
the lamination of deposit. Close-set joints likewise give rise to 
divisional planes, which now and then may deceive an observer by 
their resemblance to stratification. _ | 
Originally the planes of stratification, in the great majority of 
cases, were nearly horizontal. As most sedimentary rocks are of 
marine origin, and have accumulated on the shallower slopes of the 
sea-floor, they must have had from the first a slight inclination sea- 
wards ; but, save on rapidly shelving shores, the angle of declivity has 
been usually so slight as to be hardly appreciable by the eye. 
Slight departures from this predominant horizontality would be 
caused where sediment accumulated unequally, or where the floor 
on which deposition took place was of an undulating or more 
markedly uneven character. 
False-bedding, Current-bedding.—Some strata, particu- 
larly sandstones, are marked by an irregular lamination, wherein the 

Fig. 184.—SxrctTion oF FALSE-BEDDED STRATA, 
Jamine, though for short distances parallel to each other, are oblique 
to the general stratification of the mass, at constantly varying 
angles and in different directions (ab ¢din Fig. 184). This structure, 
known as false-bedding or current-bedding, points to frequent 
changes in the direction of the currents by which the sediment was 
carried along and deposited. Sand pushed over the bottom of a 
sheet of water by varying currents tends to accumulate irregularly 
in bands and ridges, which often advance with a steep slope in front. 
The upper and lower surfaces of the bank or bed of sand (* * in 
Fig. 184) may remain parallel with each other as well as with the 
underlying bottom (a), yet the successive laminz composing it may 
lie at an angle of 30° or éven more. We may illustrate this structure 
by the familiar formation of a railway embankment. The top of the 
embankment on which the permanent way is to be laid, is kept level ; 
but the advancing end of the earth-work shows a steep slope over 
which the workmen are constantly discharging waggon-loads of 
rubbish. Hence the embankment, if cut open longitudinally, would 
present a “ false-bedded ” structure, for it would be found to consist 
