58 DIVERSIONS OF A NATURALIST 



together with the flints, and in consequence are often 1 

 stained of a fine red. Such clear red-stained chalcedony 

 is called " carnelian " ; if the banded agate structure 

 shows, it is called agate rather than carnelian. It is 

 wonderful how many beautiful pieces of both carnelian 

 and agate are picked up on the Felixstowe beach, rarely, 

 however, bigger than a hazel nut. The original source 

 of these carnelians and agates is the East of Scotland. 

 At Montrose you may see the igneous rock containing 

 pale, lavender-coloured agate nodules as big as a potato, 

 the breaking and rolling of which by the sea into small 

 bits has furnished our Suffolk carnelians. Quartzite — 

 more or less translucent, sandy-looking pebbles, colour- 

 less or yellow : jasper, black or green with red veining : 

 a fine wine-red or purple stone often veined with quartz 

 — are all more or less common, and come from northern 

 igneous rocks — possibly some from Scandinavia and 

 some from the breaking up of an ancient " breccia " of 

 the Triassic age, which still exists northwards of East 

 Anglia. 



Other pebbles very common on this shore are those 

 formed in a curious way by the sea-water from the clay 

 cliffs and sea bottom which are here present, and are of 

 that special geologic age and character known as the 

 London clay. The sea at this moment is continually 

 converting the clay of our Suffolk shore into " cement- 

 stone " by a definite chemical process. The clay and 

 many other things submerged in the sea, as Shakespeare 

 knew, " undergo a sea-change." The cement-stone used 

 to be dredged up from the sea bottom and ground to 

 make cement at Harwich. Great rock-like slabs of it 

 pave the shore at low water, and pebbles of it are 

 abundant. The curious thing is that ages ago — geo- 

 logical ages, I mean — when the sea was throwing up 



