HI.] THE STONES IN THE WALL. 87 



said in mj last chapter) was certainly laid down by the 

 estuary of some great tropic river, among palm-trees 

 and Anonas, crocodiles and turtles. 



Is the reader '$ power of belief exhausted ? 



If not : there are to be seen, capping almost every 

 high land round London, the remains of a fifth world. 

 Some of my readers may have been to Ascot races, or 

 to Aldershot camp, and may recollect the table-land of 

 the sandy moors, perfectly flat atop, dreary enough to 

 those to whom they are not (as they have long been to 

 me) a home and a work-field. Those sands are several 

 hundred feet thick. They lie on the London clay. 

 And they represent the reader must take geologists' 

 word for it a series of beds in some places thousands 

 of feet thick, in the Isle of Wight, in the Paris basin, 

 in the volcanic country of the Auvergne, in Switzer- 

 land, in Italy ; a period during which the land must at 

 first have swarmed with forms of tropic life, and then 

 grown but very gradually more temperate, and then 

 colder and colder still ; till at last set in that age of 

 ice, which spread the boulder pebbles over all rocks 

 and soils indiscriminately, from the Lake mountains to 

 within a few miles of London. 



For everywhere about those Ascot moors, the top 

 of the sands has been ploughed by shore-ice in winter, 

 as they lay a-wash in the shallow sea ; and over them, 

 in many places, is spread a thin sheet of ice gravel, 

 more ancient, the best geologists think, than the 

 boulder and the boulder- clay. 



If any of my readers ask how long the period was 

 during which those sands of Ascot Heath and Alder- 

 shot have been laid down, I cannot tell. But this we 

 can tell. It was long enough to see such changes in 



