204 NEW YORK STATE MUSEUM 



same general direction as the surface rills. Tidal rills are produced 

 by the downrush of considerable masses of water lagging behind the 

 retreating and broken surge, and it is easily conceivable that larger 

 amounts or continuous sheets of water, flowing down the strand, 

 might produce series of unbroken water channels, rather than dis- 

 continuous rill channels. This is put forward as a possible ex- 

 planation of the latter phenomenon, and as these and allied appear- 

 ances seem to be intelligible by such explanations, they are included 

 among those which are readily and deductively interpreted. 



The other class of these strand markings includes those we are 

 especially trying to interpret. Of this large class there are first the 

 striated surfaces, which are here illustrated by specimens which 

 are really less effective than that given by Professor Hall, but at the 

 same time of more variant character. Various observers, speaking 

 casually, have thought that these markings might have been due, in 

 some part at least, to more or less compressed trunks of wood buried 

 in the sand and fossilized. One might see a reason for such sugges- 

 tions upon consulting our plates 16-19, but in my judgment this 

 interpretation is absolutely excluded. There is seldom any straight 

 tree-tissue associated with these beach marks, and whenever the 

 opinion referred to has been expressed, it has generally been based 

 upon the contemplation of the wrong side of the specimen. These 

 slabs are actually grooved and furrowed in parallel lines, and these 

 groovings are of various degrees of magnitude, from coarse to 

 exceedingly fine. The surfaces of the larger grooves are not only 

 sometimes, but usually striated finely by lines parallel to them. Even 

 in our greatly reduced figures these details are very obvious and the 

 fact stands out without reasonable challenge that these markings 

 have been made by the dragging or shoving of irregular objects 

 over the surface of the wet sand; not necessarily above water, but 

 if not, then within the moderate water depths. One can conceive, 

 for example, a heavy kelp attached at its root to a stone loosened 

 from its moorings, thrown upon the strand and dragged down by 

 the suck of the undertow, producing if moving with sufficient rapid- 

 ity and without interruption, some such channelings as are indicated 

 on our plate 16, or on plate 18, which is a single deep, sharply angu- 

 lar groove. But my observation leads me to doubt if anyone ever 

 saw such an effect produced by the suggested cause. We may, 

 however, for the moment, assume that heavy objects dragged by 

 the undertow of storm waves might create such channeled strand 

 and substrand surfaces as are here indicated. 



