RAWLINSON — NEW RED SANDSTONE FOOTPRINTS. 39 



of the stratification : I am not aware that any bones, teeth, spines, 

 scales, or other osseous or enamelled parts of animals have yet been 

 found. 



The beach-line existing at the time that the footsteps were im- 

 printed may be hypothetically laid down as extending from beyond 

 Altringham on tire east, to Leasowes Castle on the west, with a 

 slight curve to the southward. It is indicated by the occurrence of 

 foot- prints and ripple-marks at the Lymm, Runcorn, and Storton 

 quarries, which lie about 10 miles apart along this line. From Al- 

 tringham to Lymm and Runcorn the supposed beach-line trends 

 somewhat to the S.W., and comes within 3 miles N. of Frodshain. 

 It then curves upwards to the N.W., and at Storton is about 2^ miles 

 S.W. of Liverpool. At Runcorn and at Storton the rock is several 

 hundred feet thick, and is divided into many beds of varying thick- 

 nesses ; the foot-impressions are confined to a few of these beds only, 

 yet all of them appear to have had the requisite materials for pre- 

 serving such markings ; namely, clay betwixt the beds of sand-rock. 

 The side of the rock upon which the raised casts of the impressions 

 are found is always downward, and upon clay, so that they are casts 

 in sandstone taken from clay upon which the impressions were in- 

 dented by the animal when in motion. 



It may be asked, how it is that foot-impressions are not found on 

 the whole of the beds in the same quarry ? The following are a few 

 reasons which may be brought forward in answer to this question : — 



1st. The stratification is so marked as to bear all the evidence of 

 having been a tidal beach, probably a portion of an estuary to some 

 great river, barred by extensive sand-banks, and subjected to land- 

 floods surcharging the waters with mud. Hence the alternations of 

 arenaceous strata and thin clay-beds, as now found. If such has 

 been the case, it may be put thus : — As the beach-line is to the river, 

 estuary, ocean, or the whole extent of the stratified rock, so will be 

 the rarity of places producing specimens ; a chance of many hundreds 

 to one against any given quarry, opened indiscriminately, revealing 

 specimens. 



2ndly. For the full formation of the impressions several conditions 

 were requisite, and all must have been fulfilled at the same time. 

 The beach, usually of sand, must by some local change have been 

 coated with mud. That change, probably wrought by a storm or 

 land-flood, must have been succeeded by a calm, or the impi'cssions 

 would have been erased by the next tide. 



3rdly. To account for the impressions occurring at intervals, it must 

 be remembered that animals usually locate in groups, and do not 

 spread indiscriminately. 



These reasons may partially account for these or similar impres- 

 sions not appearing more frequently even in the same locality or the 

 same quarry. From the impressions being accompanied by sun- 

 cracks in the clay, it must have been the summer season ; and the 

 same heat that could crack the clay or mud would also partially 

 harden it, thereby giving it a consistency to resist the wearing 



