W. A. Richardson—The Relative Age of Coneretions. 117 
although possessing a large angle of repose, sand occurs in zones of 
relatively strong movement 
A further example is afforded from the Nottingham district, where 
pebbles frequently project from the wind-eroded surface of the 
Bunter into the overlying, laminated, Keuper sands.1 Professor 
H. H. Swinnerton kindly allows me to publish his field sketch of 
one case (Fig. la). It will be seen that the lamine are level and 
terminate abruptly at the pebble, showing no tendency to heap 
over it. 
Experiment and observation, then, seem to indicate that 
accumulation of sediment in layers, conformable in shape to a 
contemporaneous nodule, is unlikely to be frequent. However, 
such an origin of the structure admits of ready determination, for 
conformity would be confined to lamine passing above a concretion 
—those below necessarily being unaffected. I consider, on the whole, 
that the characteristic arrangement would be for thin layers to 
terminate abruptly against a nodule (Fig. 1a), and for those thicker 
than the nodule to pass in horizontal lines above it (Fig. 10). 
Before considering the remaining possibilities, it may be mentioned 
that conformity of stratification lines to the shape of a nodule has 
usually, if not invariably, concomitant phenomena. Such are smooth 
or slicken-sided contacts ; a tendency to the development of cone- 
in-cone structure in the surrounding matrix ; and miniature faulting. 
These may be fairly attributed to pressure, but whether the pressure 
is generated by nodular growth or vertical loading has not been 
established. 
These two cases were tested experimentally in the way indicated 
below :— 
(a) A cake of hard soap was embedded in a matrix, formed by 
superposed layers of different coloured plasticene. These were 
arranged so that they were thinner than the cake, and termmated, 
without initial bending, abruptly at its surface. The model was 
subjected to vertical pressure in a hydraulic machine. When 
removed from the press and sectioned vertically, the lamine were 
found to be compressed over the nodule, thinning out above and 
below, and generally conformable to the shape of the cake. The 
removal of the cake showed that smoothing of the contact had taken 
place (Fig. Ic). 
Therefore, pressure applied vertically to a contemporaneous 
nodule would be competent to cause bending of stratification lines. 
(b) The attempt to imitate a nodule “ srowing”’ in a deposit 
presented difficulties. Finally it was decided to force a steel ball 
gradually into a layer of coloured plasticene.. Suitable arrangements 
were made to prevent plasticene from squeezing up around the ball, 
as the latter was forced very slowly into the model. Since the ball 
thus entered at a poimt, and the volume of the intrusion increased 
1 Swinnerton, Proc. Geol. Assoc., vol. xxix, 1918, p. 20. 
