On rock that is much softer than that on the other side of the oolite hills: much softer, because it is much newer. We have got off the oolites on to what is called the Oxford clay; and then, I believe, on to the Coral rag, and on that again lies what we are coming to now. Do you see the red sand in that field?
Then that is the lowest layer of a fresh world, so to speak; a world still younger than the oolites--the chalk world.
But that is not chalk, or anything like it.
No, that is what is called Greensand.
But it is not green, it is red.
I know: but years ago it got the name from one green vein in it, in which the "Coprolites," as you learnt to call them at Cambridge, are found; and that, and a little layer of blue clay, called gault, between the upper Greensand and lower Greensand, runs along everywhere at the foot of the chalk hills.
I see the hills now. Are they chalk?
Yes, chalk they are: so we may begin to feel near home now. See how they range away to the south toward Devizes, and Westbury, and Warminster, a goodly land and large. At their feet, everywhere, run the rich pastures on which the Wiltshire cheese is made; and here and there, as at Westbury, there is good iron-ore in the greensand, which is being smelted now, as it used to be in the Weald of Surrey and Kent ages since. I must tell you about that some other time.
But are there Coprolites here?
I believe there are: I know there are some at Swindon; and I do not see why they should not be found, here and there, all the way along the foot of the downs, from here to Cambridge.
But do these downs go to Cambridge?
Of course they do. We are now in the great valley which runs right across England from south-west to north-east, from Axminster in Devonshire to Hunstanton in Norfolk, with the chalk always on your right hand, and the oolite hills on your left, till it ends by sinking into the sea, among the fens of Lincolnshire and Norfolk.
But what made that great valley?
I am not learned enough to tell. Only this I think we can say--that once on a time these chalk downs on our right reached high over our heads here, and far to the north; and that Madam How pared them away, whether by icebergs, or by sea-waves, or merely by rain, I cannot tell.