17 



and the curious markings found upon them. Sufficient reference 

 has already been made to the first ; the deposits occur in any or 

 every district, and they rest " uuconformably " as geologists say, 

 upon everything below ; they fill up hollows, they lie at the foot of 

 the hills, they are piled up at the mouth of valleys, or spread widely 

 over the plains. As to their composition, sometimes they are of 

 " sharp gravelly sand," at others " expanses of pebbly shingle, and 

 more generally perhaps, of variously coloured clays." In the central 

 counties of England we find " sheets of clay embedded in an open 

 gravely drift, composed of fragments of all the older rocks up to the 

 chalk, masses of which, thousand of tons in weight are embedded 

 in it. In other districts, as the middle counties of Scotland, large 

 areas are covered with a thick, dark, tenacious clay, locally known 

 by the name of " Till," and enclosing rounded and waterwom 

 boulders as well as angular fragments of all the older and harder rocks 

 — granite, gneiss, greenstone, basalt, limestone, and the more com- 

 pact sandstones. Let me call your attention especially to the 

 presence of such miscellaneous collections in one locality. One is 

 never surprised at the occurrence of blocks of stone of any size, or 

 in any number, provided they are natives, i.e., so long as they 

 belong to the district in which they aie found. We naturally 

 expect to see in our own neighbourhood blocks of the sandstone of 

 which the cliffs and inland slopes are composed. Nor do the people 

 of Cornwall feel astonished at the masses of granite scattered on 

 their hills or embedded in the ground. But suppose that such 

 blocks of Cornish granite lay strewn around Folkestone, and the 

 Folkestone sandstone rocks were on the Cornish heights, 

 then they would , be foreigners, not natives, and their 

 presence would require explanation, just as much as would the 

 presence of a colony of New Zealanders in some recess of the High- 

 lands. Most striking among such blocks are solitary specimens 

 found in Cumberland, Scotland, and Switzerland — composed of 

 stone, different to any kind known for miles around, lying like 

 solitary strangers in a strange land, or a stranded vessel on an un- 

 known shore. " Erratics " they are called — wanderers. At Pre- 

 volta, in the Alps, there rests upon hills of limestone, along with 

 thousands of others, the erratic shown on the screen, a block 50ft. 

 long, 40ft. broad, and 25ft. high, with all its edges and angles perfect; 

 it is composed of granite, and weighs about 5,600 tons. How came 

 it there? Note again on the next slide the "perched blocks," as 

 they are called, seen by every tourist in the Pass of Llanberis. 



Almost everywhere on the Jura Mountains, Sir C. Lyell tells us, 

 lie these granite, gneiss, and other crystalline blocks, which un- 

 doubtedly came across one of the widest and deepest valleys in the 

 world, from the Alps, which are fifty miles distant. How did they 



