508 Geological Society. 



long before, as the footsteps are indented by the drops of rain, but 

 to a less degree than the untrodden parts, in consequence, the author 

 conceives, of the pressure which the clay had undergone beneath the 

 feet of the animals. Ripple marks are exhibited also on the surface of 

 many sandstone strata in the same quarries ; and the rain marks as 

 well as the sharpness of many of the footsteps prove, that the clay was 

 not covered by water during the shower, or while traversed by the 

 animals ; and Mr. Cunningham, therefore, is of opinion that the con- 

 ditions necessary to the preservation of such impressions, particu- 

 larly of the rain drops, would be a return of water over surfaces 

 which had been left uncovered during an interval too short for the 

 desiccation of the laminse of clay before the shower fell ; and which 

 were sufficiently soft to receive the impressions, as well as tenacious 

 enough to retain them, until the return of the water which filled the 

 prints with sand. Anotlier condition is, that the velocity of the 

 water charged with the sand was not sufficient to overcome the 

 tenacity of the clay, or disturb the impressions of the rain drops. The 

 author adds, that Dr. Buckland has suggested to him, that the interval 

 between the rise and fall of tides over extensive sandbanks, the sur- 

 face of which was between the level of high and low water, might 

 have afforded daily occasions for the fulfilment of all the conditions ; 

 and that it is not easy to explain the alternate exposure to air and 

 submersion under water without appealing to the flux and reflux of 

 tides. 



An extract was then read from a letter addressed to Dr. Buckland, 

 by John Taylor, jun., Esq., F.G.S., on a slab of sandstone, exhibit- 

 ing footmarks, and supposed to be from the Kelsall quarry, at the 

 foot of Delamere Forest, but now in a pavement in the house of Mr. 

 Potts, of Chester. 



A letter was next read, addressed to Dr. Buckland by Sir Philip 

 Grey Egerton, Bart., M.P., F.G.S., respecting the same slab ; and 

 accompanied b)^ a tracing of the foot-marks, by Miss Potts. 



When the slab was first laid down, there were no indications of the 

 footsteps, and Sir Philip Egerton explains, in the following manner, 

 their origin in a homogeneous stone and subsequent development. 

 The weight of the animal on the soft sand compressed the yielding 

 materials in the vicinity of the foot, and the print having been 

 filled with sand, the stone, on becoming indurated, would present a 

 nearly uniform texture. Ihe action of the Aveather, on the flag 

 being exposed, would remove the softer portions of the surface, and 

 the denser parts surrounding the impressions of the feet, would resist 

 the same operation, and present in relief the outline of the foot. 



The flag contains the prints of three hind and two fore feet, the 

 latter bearing nearlj^ the same proportions to the former as in the 

 other species, but Sir Philip Egerton could not make accurate 

 measurements, because the markings are not all on one plane ; the 

 length of the stride he was also unable to determine, in consequence 

 of the impressions in the same line being all of the right foot. There 

 are distinct marks of claws on several of the toes. 



A jmper was next read, " On the occurrence of numerous Swallow 



