372 On the Geological Value of Recent Occurrences. 



have of a snake, and yon can fancy our disgust, amounting to horror, 

 at this invasion of slimy things crawling upon us. All the salt 

 water fish have left the hay, and all the oysters have, like good men, 

 died in their heds." 



Another remarkable modern illustration of ancient work I 

 have lately met with a slight note of in a paper of the day. In 

 a comparatively recent eruption of one of the Icelandic volca- 

 noes, a stream of lava making its way to the sea, caught up and 

 embedded in its flow the recent shells and pebbles of the beach. 

 Some specimens of this lava, lately shown to me by Captain 

 Campbell, contained this beach-debris, and reminded me forci- 

 bly of the layers of volcanic ash, contemporaries in time of far 

 gone Silurian ages, which lie inter- stratified with the sea beds 

 they intruded on through Northern Wales. 



Another exceptional modern event — may it be the last of its 

 kind ! which has been made to do good service in the geological 

 cause was the bursting of the Holmfirth reservoir ; by observing 

 the effects of which, in moving huge stones and re-laying the 

 transported material along the course of the flood, Mr. Prestwicli 

 was enabled to throw light upon the power and effects of water- 

 action similarly confined in geological times.* 



These cases I have noted, however, may truly be regarded 

 as exceptional ones, though by their prominent character their 

 power of teaching is the greater; but, as they illustrate the 

 kind of phenomenon which it will be instructive to study when- 

 ever opportunity presents, I have quoted them in illustration of 

 the work. In an excellent paper upon " Trails, Worm-markings, 

 and Tracks/' contrrtmted by my friend Professor Rupert Jones 

 to the Geologist of last month, much valuable material for study 

 is pointed out, and he shows most clearly, by direct teaching 

 and by inference, that by the use of a modern key we read the 

 Nature-printed hieroglyphs of the past. 



Geological Society of London, May 1862. 



* Journal of the Geological Society, vol. viii. p. 225. 



