716 



GEOLOGY. 



other cases they are irregular and elongated in a particular direction, as if the drops had 

 struck the surface obliquely, indicating a wind accompanying the rain. The same appear 

 ances occur in the formation near Shrewsbury. Professor Hitchcock mentions specimens 

 of sandstone in his possession, obtained from various parts of the United States, which show 

 footprints, ripple-marks, and rain-drops, the latter evincing, by a uniform elongation of 

 shape, the direction of the wind when the rain fell. 



Walking along our shores in the present day, we observe a well-defined cast of our own 

 footstep left in the sand still wet from the retreating tide, and similar distinct impressions 

 made by the passage of animals and birds across it, and by the descent of a violent shower 

 of rain upon it. In the same manner it is probable that the tracks which the new red 

 sandstones present, were formed on the shores of an estuary, or a tidal river, between high 

 and low water mark then dried and hardened by the action of the sun and air during 

 the recession of the waters the returning waves washing up silt to cover up the impres 

 sions, the two layers uniting, to exhibit, if ever separated, the one a mould and the other 

 a cast from it, of the forms that have been there. The observation of phenomena now, 

 similar to that unfolded by the old rock-systems, is of no mean importance and interest 

 to mankind, in every condition of society. Many a depredator has been detected by the 

 correspondence of his foot to its imprint in the snow or loose earth near the place of 

 his crime. The North American Indian finds his enemy by his trail, and can not only 

 distinguish between the elk and the buffalo by the marks of their hoofs, but determine 

 with great exactness the space of time that has elapsed since the animals have passed. 

 In the deserts of Africa the track of the camels proclaims to the Arab whether a heavily 

 or lightly laden caravan has crossed the sands. But from the simple imprints presented 

 by these ancient formations, we gather information relating to thousands, nay, tens of 

 thousands of years ago catch a glimpse of the animals that then existed, no vestige of 

 whose actual forms remains and have even the pattering of the shower and the direction 

 of the wind indicated to us. 



Dipterus, from the Old Red Sandstone, described at p. 689. 



