BELOW THE TIDEMARK 273 



They recall the clouds of a mackerel sky, and the likeness 

 is not misleading. The rippling pattern of many cloud for- 

 mations is due to the undulating flow of a current of warm 

 air at the level where cold causes condensation. The crests 

 of the waves are chilled into cloud, while the troughs retain 

 their free vapour. The undulations of the sea in the breeze 

 are registered in the floating layer of sand, which keeps, 

 when it solidifies, the print of the last ripple that touched it. 

 Though moulded by a momentary ripple, and obliterated in 

 the normal course after a few hours, the ripple-marks on 

 primaeval beaches have yet survived in stone among the 

 fossils of ancient rocks. Where blocks of ripple-marked 

 sandstone overhang a modern beach, the contrast adds a 

 doubly sensitive charm to the sands bared below at each 

 tide. 



The essential beauty of the sands is in their cleanness and 

 freedom, and they need adornment even less than the clean 

 turf of an old lawn. When we tread them at low-water most 

 of their resident life has gone into hiding, either beneath the 

 surface or in the pools scooped by the falling tide. But their 

 smooth expanse is flecked with signs of activity which suggest 

 the hidden vitality of the spot. Sea-worms have thrown 

 their casts of sand like the heaps of the earth-worms on a 

 lawn, and their number is suggested by the abundance of 

 these little piles after each tide. In the wet sand near low- 

 water mark the flexible tubes of the terebella emerge on the 

 surface like large caddis-shells. The bristly sluglike sea- 

 mouse, occasionally seen striking out of the wet sand, is 

 a larger and more rapacious worm. Jelly-fish evaporate in 

 the sun to a mere patterned film, and the track of the star- 

 fish leads like the print of a rope to the pool under the weed- 

 hung pile where it found a refuge as the tide fell. The 

 nettlelike sting of the larger red and purple jelly-fishes is 



