60 



Recent Excavations at Stonehenge. 



they were found would have so greatly diminished their weight 

 and the difficulties of their transport ? The same people, as we 

 have seen, in dealing with the blocks of sarsen-stone (which were 

 probably moved only a few hundreds of yards) would appear to 

 have left only the final dressing to be done after their transport, and 

 to have reduced their weight as far as possible before removal. 



I have long believed that the explanation of the true source of 

 these " foreign rocks " is to be found in the circumstance that such 

 materials are constantly found transported as boulders of the 

 glacial-drift. It is true that the " southern limit of the boulder 

 clay " is usually placed by geologists considerably to the north of 

 Wiltshire ; but it is a well-known fact that scattered boulders 

 often occur far to the south of this limit. The sheets of boulder 

 clay which now cover so large a part of the country are merely 

 relics of an originally much more widely spread formation. 



In many places the boulder clay has been greatly diminished in 

 thickness by denudation, and deep valleys have been cut through it by 

 the existing rivers. Many tracts where the boulder clay was thin 

 have probably been swept quite bare of the formation, except for 

 the large boulders that would be left behind. A proof of this is 

 found in the fact that the gravels of the rivers of the South of 

 England, including those which drain Salisbury Plain, contain 

 many fragments of " foreign rocks " which must have been derived 

 from the boulder clay, and among these it would not be difficult to 

 select representatives of the " bluestones " and fragments from the 

 soil of Stonehenge. I have myself seen a boulder of a slaty rock, 

 comparable in size to the largest of the " bluestones " of Stonehenge, 

 on the hills to the south of London. 



It may doubtless be objected that such large boulders of foreign 

 rock do not now occur anywhere upon Salisbury Plain. But it 

 must be pointed out that rocks of considerable hardness and 

 durability are everywhere sought for and utilised for millstones, 

 gate-posts, and for road-metal. Even the widely distributed sarsen- 

 stones are rapidly disappearing, the blocks, especially the harder 

 ones, being broken up and carried away for building-stones and 

 road-metal; and it is certain that the much more sparsely distributed 



